Chapter 80

Patient Positioning and 

Precautions During 

Anesthesia and Surgery 

80 

CHAPTER 

Ahmed Mohamed Shalabi 

INTRODUCTION 

Proper patient positioning is an important but often overlooked 

part of the surgical plan. It not only allows optimal surgical 

exposure and reduces surgeon fatigue but also ensures the patient’s 

comfort and protection from injury. Physiologic changes that 

occur as a result of positioning have their origins primarily in 

gravitational effects. 

GENERAL GUIDELINES AND 

PRECAUTIONS FOR POSITIONING 

Frequently, a small child is happy to sit up and play but has no 

intention of lying down on the operating table. In such cases, it is 

much better to proceed with induction with the child sitting up 

near the upper edge of the operating table and his or her back 

supported by the anesthesiologist’s chest or arms or resting on her 

or her lap. This should not be considered a mandatory approach 

for induction of anesthesia, but rather, one method out of many 

that reduces stress and anxiety for the child. Of course, the choice 

depends on the medical condition, the type of premedication used, 

and the surgical situation. For instance, preoxygenation is more 

effective in 25 degrees head-up position than in supine position in 

severely obese patients and/or patients with poor pulmonary 

reserves. 1 The following considerations must be observed before 

beginning the anesthesia: (1) ensure that the operating room table 

is working properly; (2) ask the surgical personnel about the 

position of the patient for surgery; (3) ensure that help will be 

available for positioning and communicate clearly the different 

steps to achieve position before the patient is moved to avoid 

personnel injuries; (4) prepare all needed material and equipment 

for positioning (e.g., padding, rolls, blankets, tape); (5) move the 

patient slowly while protecting the airway, intravenous lines, 

drains, monitoring cables, and other equipment; and (6) once the 

patient is positioned, recheck everything, particularly to ensure 

proper lung ventilation and avoid pressure points and neuro - 

vascular compressions. The anesthesiologist is responsible at all 

times for the airway equipment and the handling of the head of the 

patient. In this position, she or he can better guide the positioning 

of the patient and ensure safety during this precarious maneuver. 

Many anesthesiologists prefer disconnecting the monitor cables 

and intravenous and arterial lines just before positioning in order 

to prevent accidental removal or kinking. It helps, while recon - 

necting the monitoring cables and vascular lines, to ensure proper 

functioning, prevent pressure points, and provide proper padding 

to protect the patient against potential injury. 2 However, to mini - 

mize the time while the patient is not monitored, it is recom - 

mended to remove the pulse oximeter just before positioning and 

replace it immediately after positioning. Proper lung ventilation 

should be confirmed immediately by capnography and chest 

auscultation. The team should be prepared to return the patient to 

the supine position immediately if, for unknown reason, the 

patient’s safety cannot be ensured in this new position. General 

review of the items that should be checked and verified during a 

positioning process is listed in Table 80–1. 

The following anesthetic considerations are the basic principles 

for selecting the patient’s final position for the surgical procedure: 

A 

B 

C 

D 

E 

TABLE 80-1. Positioning and Repositioning Checklist 

Airway 

Breathing 

Circulation 

Disability/ 

neurology 

Exposure 

Endotracheal 

tube/LMA 

Ventilation 

Auscultation 

Monitoring 

Monitoring 

Intravascular 

lines 

Eyes Neurovascular 

All cables, 

catheters, 

and 

electrodes 

Access 

Patent and in correct 

position 

Satisfactory lung 

compliance 

Axillary lines bilaterally 

SaO 2 

Capnography trace and 

shape 

Check that HR/BP/ECG 

are still functioning and 

readings are stable 

All still in situ, patent and 

accessible 

Closed and protected, 

padded vulnerable 

areas, and avoidance of 

excessive passive stretch. 

Avoid compression of 

male genitalia and 

female breasts. 

Checked and removed 

from the patient/ 

operating table interface 

Maintain access for review 

of at risk areas if possible 

BP = blood pressure; ECG = electrocardiogram; HR = heart rate; LMA = 

laryngeal mask airway; SaO 2 

= arterial oxygen saturation.

1342 PART 4 ■ Special Monitoring and Resuscitation Techniques 

(1) Does the position allow proper surgical exposure? (2) Does 

the position allow access to the airway at all time, to vascular 

access, and monitors? (3) Does the position stretch muscles or 

hyperextend joints unacceptably? (4) Does the position increase 

the risk of pressure points on the skin or neurovascular structures? 

(5) Is ventilation and/or circulation compromised? (6) Does the 

position respect the patient’s physiologic condition? and (7) Does 

the position affect the proposed anesthetic technique and increase 

the risk of complications related to the suggested position. 

For instance, the position chosen for the administration of 

spinal anesthesia should ensure that the head of the patient is 

neither up nor down to prevent sudden hemodynamic complica - 

tions if the head is down, allowing for the local anesthetic to move 

upward; or an insufficient block level if the head is up, allowing 

the local anesthetic to move downward by gravity. 

Figure 80-2. The “lawnchair” position. The advantage of the 

position lies in the comfort of the awake or sedated patient 

because the weight of the body is more evenly distributed, and 

in addition, it permits less strain at the hips and knee joints. 

SUPINE POSITION 

General Considerations 

The supine position is the most commonly used surgical position. 

It is well tolerated and causes no important effect on the phy - 

siologic systems in normal adults and children. It is normally used 

in most circumstances at the beginning of anesthesia to the secure 

the airway, ensure proper lung ventilation, and place vascular 

access and monitoring equipment. However, because the head of 

an infant and a small child is large in comparison with the trunk, 

it is highly recommended to use a head ring (the shape of a donut) 

and a roll under the shoulders to maintain the head in position 

for induction and airway management. Furthermore, the use of 

this roll under the shoulders will limit the neck flexion and 

improve airway patency. 

Variation of Supine Positions 

With the traditional supine position, the patient lies on his or her 

back and the head is supported on a pillow. The arms are placed 

by the side of the body or rest on outstretched armboards. The 

weight of the patient rests on the occiput, back and scapula, 

sacrum, dorsal legs, and heels (Figure 80–1). There is a loss of the 

normal lumbar lordosis that may lead to postoperative backache 

and is usually associated to the duration of the surgery. With the 

contoured supine/lawnchair position, the hips and knees are slightly 

flexed into an anatomically neutral joint position using soft rolls 

underneath the knees, reproducing the position assumed when 

one is resting in a reclining chair. This is a more natural position, 

especially during prolonged surgical procedures. With a pillow 

beneath the shoulders and the head slightly elevated above the 

level of the atrium, a reduction of cerebral venous pressure is 

ensured. This posture should be considered over the traditional 

supine position for the older and larger child (Figure 80–2). Care 

should be taken to ensure that the venous return from the lower 

limbs is not jeopardized by external compression. The frogleg 

supine position is achieved by simultaneous flexion of the knees 

and hips while the hips are externally rotated, bringing the heels 

together in the midline. The thighs are externally rotated at the 

hips. Pillows are placed beneath the knees and on the lateral sides 

of the thighs and lower legs (Figure 80–3). This posture allows 

procedures to be performed on the medial thigh, genitalia, and 

perineum. The supine hanging leg position is used during opera - 

tions involving the knee joint with the patient moved to the end of 

the operating table, allowing the knee to overhang the edge of the 

table. 

Physiologic Effects of the Supine Position 

The normal hydrostatic effect of gravity on venous return is insi - 

gnificant in the supine position. As a result, the change of posture 

from an erect to a supine position results in an initial increase in 

venous return with a subsequent increase in pulmo nary perfusion 

and an increase in cardiac output and arterial pressure. This effect 

is not sustained because compensating mechanisms (via arterial 

baroreceptors in the walls of the aorta and the carotid arteries) are 

initiated, resulting in the reduction of heart rate, stroke volume, 

peripheral resistance, and mean arterial pressure (MAP). Regional 

Figure 80-1. Supine position. 

Figure 80-3. The “frogleg” supine position allows excellent surgical 

exposure to the perineum and groin. Excessive strain or 

stretch at the hip joints is minimized by supporting the lateral 

aspects of the legs.

CHAPTER 80 ■ Patient Positioning and Precautions During Anesthesia and Surgery 1343 

pulmonary circulation is mainly distributed within the lung below 

the right atrium. Preferential perfusion to the dependent lung 

areas remain unchanged in awake and anesthetized patients. There 

is a reversal of the dependence ventilation in the conscious patient 

to that of the increased ven tilation to the nondependent portions 

of the lungs in anesthetized patients, resulting in an increased in 

the ventilation-perfusion (V˙/Q˙) mismatch and, consequently, 

hypoxemia. 

The effect of gravity accounts for the majority of the physiolo - 

gic changes in the supine position with alterations in respiratory 

mechanics, ventilation, and perfusion. In the upright posture, the 

position of the diaphragm is determined by the balance of forces 

between the cephalad pull by the lungs’ elastic recoil forces and 

the caudad pull by the weight of the abdominal contents. The 

diaphragm is displaced cephalad owing to the combined forces of 

the lungs’ elastic recoil and the hydrostatic forces of the abdominal 

contents. During quiet breathing in the awake subject or spon - 

taneous respiration in an anesthetized patient, there is only a 

minor cephalad shift of the diaphragm dome. However, anes - 

thetized and paralyzed patients show greater cephalad shift, with 

the dorsal part of the diaphragm most significantly displaced. 3 

Studies in the pediatric population demonstrated similar 

respiratory alterations with postural changes. In healthy children, 

the functional residual capacity (FRC) in the supine position is 

lower than sitting FRC by 25 to 30%. 4 Hypoxemia may occur if 

the FRC is less than the closing volume and small airway closure 

occurs during exhalation. Some small airways will in fact be closed 

throughout the respiratory cycle, leading to a reduction in lung 

compliance. The closing volume is much higher in neonates and 

infants because of the decrease in elastic tissues present in the 

lungs. Consequently, in infants, the small terminal alveoli at the 

dependent portions of the lungs would be closed by atelectasis at 

the end of each breath. Healthy infants can overcome this 

tendency by constant activity and crying. As in adults, induction 

of anesthesia is associated with a significant reduction in the FRC. 

Computed tomography (CT) revealed that atelectasis occurs on 

induction of anesthesia in pediatric patients. 5 Anesthesia with 

spontaneous breathing increased the volume of atelectasis mea - 

sured whereas anesthesia with mechanical ventilation significantly 

decreased the volume of atelectasis present at end-expiration. In 

anesthetized-paralyzed healthy adults, the amount of atelectasis 

formation in dependent lung regions could be as much as 16 

to 20% of the normal aerated lung tissue as seen on spiral CT. 

The distribution of atelectasis is nonhomogeneous, with the 

amount of atelectasis greatest near the diaphragm and less at 

the apex of the lungs. This suggests that relaxation and cranial 

shift of the diaphragm that compresses the dependent portion of 

the lungs could be responsible for the formation of these atelectatic 

regions. 6 

Atelectasis is an important cause of impaired gas exchange 

during general anesthesia because it causes pulmonary shunting 

and regions with low V˙/Q˙ ratios. The pulmonary shunt increases 

up to 12% and is located in dependent lung regions corresponding 

to the atelectatic areas. Atelectasis development occupied 0.6 to 

7% of the intrathoracic area. Increasing tidal volumes will abolish 

the reduction in FRC and minimize the degree of atelectasis. Reexpansion 

of the atelectatic regions by the application of positive 

end-expiratory pressure (PEEP) has also been shown to be effec - 

tive in reversing atelectasis and improving arterial oxygenation. 7 

The institution of muscle paralysis and intermittent positivepres 

sure ventilation results in preferential ventilation to the non - 

depen dent portions of the lungs. However, the anesthetic agent may 

play an important role in the changes in lung volumes. For instance, 

the FRC did not change during induction of anesthesia with 

ketamine in children who were spontaneously breathing. 8 Similar to 

adults, total respiratory compliance is decreased after induction of 

anesthesia in supine infants breathing spontaneously. This can be 

prevented by increasing tidal volume in the paralyzed children to 

match tidal volumes of these infants during the sedated state. 9,10 

Complications of the Supine Position 

Several skin surfaces are placed at risk for injury from direct 

pressure (Figure 80–4). Decreased skin blood flow may favor 

blistering and skin necrosis. In small infants and children, the 

scalp is at risk during prolonged anesthesia in the supine position. 

Most often, the occipital area bears the full weight of the head, 

creating the potential for pressure-induced ischemia and hair loss. 

Alopecia (circular bald spot) may appear only days or weeks after 

the procedure. Even the adequate padding may not prevent this 

injury during very long procedures. Lifting the head and massag - 

ing the scalp briefly or turning the head at reasonable intervals 

seem appropriate to prevent this problem. Supraorbital nerve 

compression from the anesthetic ventilation circuit or tracheal 

tube or from pressure from the facemask or strap placement may 

lead to permanent supraorbital paresthesia. Coexisting medical 

problems (e.g., diabetes mellitus, uremia, hypothyroidism, polycythemia 

vera, hypothermia) may also contribute to nerve injury. 

The potential causes of nerve injury include: 

● 

● 

● 

● 

Section (e.g., type of surgery [sternotomy]). 

Compression (e.g., prolonged tourniquet [>2 h]). 

Traction (e.g., prolonged position (>4 h lithotomy]). 

Ischemia (e.g., congenital anomalies [cervical rib and thoracic 

outlet syndrome]). 

Figure 80-4. Area at risk for pressure 

point injuries in the supine 

position. A: Scalp over the occiput. 

B: Condylar groove. C: Skin over 

the sacrum. D: Area over the 

Achilles tendon and foot. 

1 2 3 4


● 

● 

Neurovascular compromise: 

• Compression or stretching of intraneural vasa nervorum— 

neural ischemia. 

• Nerve has a long or superficial course between two points of 

fixation. 

• Stretching and compression combined—worst. 

• Tissue edema from intravenous fluid may contribute to neurovascular 

compression. 

Equipment malfunction is another cause of problems, especially 

tourniquets, blood pressure cuffs, infusion pumps or armboards. 

The brachial plexus is at risk from pressure-induced ischemia 

and stretch injury, and it is the second most common nerve injury 

reported under anesthesia. The most common mode of brachial 

plexus injury is through excessive stretching of the nerves. Stretchinduced 

neuropathy of the brachial plexus remains a frequently 

preventable complication. The arms of the patient are frequently 

abducted and externally rotated for ease of access to the monitors 

and intravenous access. With the arm held in constant abduction, 

flexion of the neck to the contralateral side puts the brachial plexus 

under tension with the head of the humerus being a pivot point for 

the stretch. Neurapraxia may result. Modification of the supine 

position with the arm suspended above the head may also result 

in stretch injury to the brachial plexus when extreme abduction or 

anterior flexion of the arm is performed and especially if com - 

bined with contralateral neck rotation. The anesthesiologist should 

always be vigilant to guard against extremes of movement during 

the course of the surgical procedure to minimize the risk of peri - 

operative neuropathy. In adult patients, brachial plexus formed 

the second most common site of anesthesia-related nerve injury in 

the American Society of Anesthesiologists (ASA) Closed Claims 

Database (20% of 4183 claims). 11 The diagnosis is established on 

the basis of pain, numbness, and decreased movement noted 

immediately postoperatively to 48 hours postsurgery. Brachial 

plexus injury may present in the first postoperative day with pain 

in the neck and upper arm accompanied by sensory anesthesia 

and motor function loss. Commonly, only the upper roots (C5–7, 

Erb’s palsy) with upper arm and forearm are involved. Rarely, the 

lower roots (C8–T1) with predominantly hand involvement or the 

whole plexus may be damaged. Full recovery is expected if incom - 

plete lesions are present, although regeneration may take 3 to 6 

months. If there is no evidence of activity, stretch injuries may 

have a poor prognosis because not only are the axons injured but 

also the tubular conduits, which permit regeneration, are affected. 

In 2000, the ASA published a practice advisory for the prevention 

of perioperative peripheral neuropathies. 12 This advisory made 

several recommendations that may decrease the incidence of 

neuropathies and are listed in Table 80–2. 

Ulnar nerve injury accounts for nearly one third of all nerve 

injuries associated with anesthesia and is the most common 

anesthesia-related neuropathy. Traction injury occurs with exten - 

sion and lateral displacement of the neck, with resultant increased 

TABLE 80-2. Summary of Task Force Consensus by the American Society of Anesthesiologists 

Preoperative Assessment 

● When judged appropriate, it is helpful to ascertain that patients can comfortably tolerate the anticipated operative position. 

Upper Extremity Positioning 

● Arm abduction should be limited to 90 degrees in supine patients; patients who are positioned prone may comfortably tolerate 

arm abduction > 90 degrees. 

● Arms should be positioned to decrease pressure on the postcondylar groove of the humerus (ulnar groove). When arms are 

tucked at the side, a neutral forearm position is recommended. When arms are abducted on armboards, either supination or a 

neutral forearm position is acceptable. 

● Prolonged pressure on the radial nerve in the spiral groove of the humerus should be avoided. 

● Extension of the elbow beyond a comfortable range may stretch the median nerve. 

Lower Extremity Positioning 

● Lithotomy positions that stretch the hamstring muscle group beyond a comfortable range may stretch the sciatic nerve. 

● Prolonged pressure on the peroneal nerve at the fibular head should be avoided. 

● Neither extension nor flexion of the hip increases the risk of femoral neuropathy. 

Protective Padding 

● Padded armboards may decrease the risk of upper extremity neuropathy. 

● The use of chest rolls in laterally positioned patients may decrease the risk of upper extremity neuropathies. 

● Padding at the elbow and at the fibular head may decrease the risk of upper and lower extremity neuropathies, respectively. 

Equipment 

● Properly functioning automated blood pressure cuffs on the upper arms do not affect the risk of upper extremity neuropathies. 

● Shoulder braces in steep head-down positions may increase the risk of brachial plexus neuropathies. 

Postoperative Assessment 

● A simple postoperative assessment of extremity nerve function may lead to early recognition of peripheral neuropathies. 

Documentation 

● Charting specific positioning actions during the care of patients may result in improvements of care by (1) helping practitioners 

focus attention on relevant aspects of patient positioning and (2) providing information that continuous improvement processes 

can use to lead to refinements in patient care.


traction on the contralateral brachial plexus, or when the arm is 

abducted more than 90 degrees with posterior displacement that 

will increase tension of the ipsilateral ulnar nerve. At the elbow, the 

ulnar nerve runs superficially behind the medial epicondyle of the 

humerus (condylar groove); at this location, direct prolonged 

compression or indirect compression during elbow flexion due to 

stretch of the cubital tunnel retinaculum between the medial 

epicondyle and the olecranon process can render the nerve 

ischemic with resultant neurapraxia. Positioning the arm and wrist 

dorsally and in extension to secure an indwelling arterial catheter 

may also lead to compression of the nerve at the wrist. Injury to 

the ulnar is disabling, because the small muscles of the hands will 

be paralyzed. Vigilance is mandatory to keep the elbow well 

padded and the position of the arm noted at all times during the 

surgical procedure. Unfortunately, treatment of established lesions 

has yielded mixed results. 13 

Median nerve injury results from extreme wrist dorsiflexion or 

from extravasations in the antecubital fossa. Very tight blood 

pressure cuffs and upper limb tourniquets can cause radial nerve 

injury. 

Lower limb neuropathies are more common in the lithotomy 

position than in neutral supine positions. In the supine patient, 

injury to the sciatic nerve is uncommon; however, it could result 

from a direct stretch or compression secondary to strangulation of 

its blood supply. This complication can lead to a compartment 

syndrome. Positioning of the buttock over an edge of the operating 

table or on beanbags placed to elevate and stabilize the leg during 

arthroscopy can result in compression injury to the sciatic nerve. 

The common peroneal nerve, a branch of the sciatic nerve, can be 

damage by direct pressure around the neck of the fibula. The 

common peroneal nerve is more frequently affected than the 

sciatic. All muscles below the knee are paralyzed and the patient 

will present with a footdrop. There is also loss of sensation below 

the knee except for the area distributed medially supplied by the 

saphenous nerve. Femoral neuropathy can result from improper 

placement of abdominal wall retractors, which causes direct com - 

pression of the iliopsoas muscle resulting in direct compression 

of the nerve, or from occluding the external iliac vessels or pene - 

trating vessels, causing ischemic injury to the nerve. 

Management of postoperative neuropathy can be carried on as 

follows: 

1. If a sensory disorder is present usually in the form of numbness 

and/or tingling, reassure the patient because it usually resolves 

during the first 5 postoperative days. If it persists for longer 

than 5 days, consult a neurologist. 

2. If a motor disorder is present, consult a neurologist imme - 

diately. Usually, neurophysiologic studies are done as electro - 

myography and nerve conduction studies. 

Improper handling and positioning of the head and neck in 

certain patients such as those with Down syndrome, achondro - 

plasia, Morquio-Brailsford syndrome, or cervical instability may 

predispose to cervical cord complications. The range of movement 

for flexion, extension, and lateral flexion should be determined 

before anesthesia, and the limits of motion, especially flexion and 

extension, avoided. Extremes of position (rotation, lateral flexion) 

and improper care during patient movement also place the 

cervical spine at risk. When transferring the anesthetized patient, 

it is important that the head move as one unit with the trunk, 

because “whiplash” injury may occur if the trunk moves faster 

than the head and neck. Hyperextension of the knee may result in 

ligament stretch and pain over the posterior joint capsule. Com - 

partment syndrome of the lower limbs is a very rare complication 

in a patient lying in the supine position. This may occur, however, 

when the calves are resting on a hard cushion used to maintain 

knee flexion during a lengthy procedure, leading to rhabdomyoly - 

sis and myoglobinuria. 14 

HEAD-UP TILT POSITIONS/REVERSE 

TRENDELENBURG POSITION 

Physiology of the Head-Up Tilt/Reverse 

Trendelenburg Position 

Changes in respiratory system mechanics are relatively small in 

healthy awake subjects owing to adaptability of total chest wall 

mechanics. A change of posture from the supine to a 30-degree 

head-up tilt results in a negligible decrease in the chest wall and 

lung elastances and improved compliance 15,16 but increases the 

FRC by nearly 20%. In a healthy anesthetized adult, the head-up 

tilt results in a significant reduction of cardiac output and MAP of 

up to 40% compared with the supine position. The heart rate and 

peripheral vascular resistance are slightly increased because filling 

pressures are reduced significantly. Echocardiographic indices of 

preload, as measured by left ventricular end-diastolic area, are also 

decreased, changing in the same direction as the pressure indices. 17 

This is associated with a decrease in intrathoracic and pulmonary 

blood volume by 14% and 17%, respectively. The decrease is 

probably due to a shift of blood volume toward extrathoracic 

compartments, especially the dependent lower limbs. The creation 

of a pneumoperitoneum during laparoscopic surgery on the upper 

abdominal viscera results in a reduction of 13% in cardiac output 

in anesthetized-paralyzed patients placed in a 20-degree reverse 

Trendelenburg position. 18 The effects of carbon dioxide (CO 2 

) 

pneumoperitoneum are a reduction in cardiac index of 3% and 

stroke volume of 10% and an increase in both heart rate and MAP 

of 7% and 16%, respectively. Head-up tilt of 20 degrees further 

decreased cardiac output by 11% and stroke volume by 22% 

whereas heart rate increased by 14% and MAP by 19%. 19 The 

mechanisms that result in these hemodynamic changes are com - 

plex and include direct mechanical effects, neurohumoral 

responses, and absorbed CO 2 

. 

The respiratory effects are well documented. The total com - 

pliance of the lungs may be reduced up to 48% due to the cephalad 

shift of the diaphragm caused by the insufflated gas. 20 This is 

without significantly altering the intrapulmonary distribution of 

ventilation and perfusion. 21 Although the reverse Trendelenburg 

position increases FRC and, presumably, compliance, oxygenation 

does not necessarily improve. 22 This is probably because of the 

reduction in cardiac output, which occurs in the head-up tilt, 

negating the beneficial effects of position on the distribution of 

ventilation. There are limited data regarding the effects of reverse 

Trendelenburg position in the pediatric population. One report 

on 25 children aged 1 to 14 years undergoing laparoscopic fundo - 

plication showed that 3 patients developed hypotension or 

bradycardia occurring before peritoneal insufflation. 23 Transient 

hypotension was probably related to hypovolemia. One bronchial 

intubation episode developed as a result of the positional change 

and the creation of the pneumoperitoneum.


central nervous system pathology and essentially useless for vas - 

cular volume resuscitation. 

Physiology of the Trendelenburg Position 

Figure 80-5. Reverse Trendelenburg position. 

Complications of the Head-Elevated Positions 

The complications associated with the head-elevated prone posi - 

tion or the head-elevated supine position are similar to that known 

to the traditional prone and supine positioning (Figure 80–5). 

Beside the complications that might arise as a result from the 

physiologic changes with repositioning, ophthalmic complications 

from compression of the eye from a headrest is feared in the headelevated 

prone position. Proper strap placement at the edge of the 

buttocks must be used to prevent the patient from sliding down 

the tilted table. The strap should be positioned between the 

femoral head and the iliac crest to avoid compression of the 

vascular bundle crossing the hip joint and causing ischemic necro - 

sis of the femoral head, or the strap may be applied 2 inches distal 

to the knee. Because the head is elevated above the level of the 

heart, the risk of air embolism is present, although it is signifi - 

cantly less than that observed in the classic sitting position. Appr - 

opriate monitoring should be instituted. Cerebral perfusion and 

blood flow may decrease. 

TRENDELENBURG POSITION 


The steep 45-degree head-down tilt surgical posture was 

popularized in the 1870s by Friedrich. Trendelenburg as a means 

of improving access to pelvic pathology as the abdominal contents 

shifted cephalad with gravity. The eponym “Trendelenburg” now 

encompasses any degree of head-down tilt, regardless of whether 

the patient is lying supine, lateral, or prone (Figure 80–6). All 

head-down tilt positions are now recognized, however, as poten - 

tially harmful in the presence of cardiac, pulmonary, ocular, and 

Figure 80-6. Trendelenburg position. 

Walter Cannon advocated the value of the Trendelenburg position 

in the management of cardiovascular shock during the early 1900s. 

The belief was that any head-down tilt increased venous return 

and improved cerebral blood flow. But placing the adult patient 

in a mild 15-degree Trendelenburg position resulted only a 1.8% 

displacement of the total volume centrally; this small amount is 

unlikely to have an important clinical effect. 24 Subsequent studies 

also questioned the validity of this posture in the management of 

shock when patients who were hypotensive had worsening of 

hemodynamic parameters and increased mortality when they 

were placed in the Trendelenburg position. 25 In healthy normo - 

tensive volunteers and patients, the head-down tilt resulted in an 

increase in the filling pressures of the heart, no change or a slight 

increase in the cardiac output, and no significant change in the 

arterial pressure as the carotid and aortic baroreceptors induced 

systemic vasodilatation and a slight decrease in pulse rate. 26 The 

increase in cardiac output, if any, results from the increase in 

stroke volume from the initial increase in venous return, but this 

effect is short-lived and disappeared within 10 minutes. 27 The 

cardiac output may increase or more commonly be reduced when 

hypotensive patients are placed in a head-down tilt. Significant 

decrease in the arterial pressure was observed when the cardiac 

varied from +52% to 14% in a group of hypotensive patients 

placed in a 10-degree Trendelenburg tilt. 24 No significant impro - 

vement in oxygen delivery or oxygen extraction ratio in hypoten - 

sive critically ill patients placed in the Trendelenburg position was 

observed. The mild increase in blood pressure is not associated 

with an improvement in blood flow or tissue oxygenation. 28 In 

nonanesthetized patients, no changes are found in cardiac output, 

MAP, systemic vascular resistance, and oxygenation when 

they were placed in 10- or 30-degree Trendelenburg position. 29 

Although most studies confirm that the Trendelenburg position in 

healthy anesthetized patients does not result in any sustained 

hemodynamic changes, peritoneal insufflation with CO 2 

results 

in a significant increase in systemic vascular resistance as well as 

a significant decrease in cardiac index and ejection fraction area 

compared with baseline. 17,26 The mild Trendelenburg position is 

often used during insertion of a central venous line, possibly by 

making the jugular veins less collapsible because of increased 

intravascular pressure. The diameter of the internal jugular vein 

(IJV) was shown to increase with the head-down tilt, but this 

maneuver was less effective when compared with the application 

of an abdominal binder or the use of a Valsalva maneuver. 30 A 

head-down tilt of more than 20 degrees does not increase crosssectional 

area of the IJV any further, whether or not hepatic 

compression is applied. Hepatic compression and positive inspira - 

tory pressure caused by a Valsalva maneuver effectively dilate the 

IJV, which facilitates venous cannulation in supine patients when 

the Trendelenburg position is not advisable or possible. 31 It was 

found that, in the pediatric age group, inguinal compression 

effectively increases the cross-sectional area of the femoral vein; its 

effect is also prominent in the Trendelenburg position. Valsalva 

maneuver is more effective in smaller children younger than 2 

years. Gravitational position changes alone have little effect on the 

size of the femoral vein in children. 32


The most significant effect of the Trendelenburg position on 

the respiratory system is the mechanical interference with chest 

movement and the limitation of lung expansion. With the head 

and chest at a level lower than the abdomen, the weight of the 

abdominal viscera will impair diaphragmatic movement and 

reduce lung volumes. A 10-degree head-down tilt causes a 3% 

decrease in tidal volume, whereas a 20- or 30-degree Trendelen - 

burg position resulted in a 12% reduction. A significant increase 

in the physiologic deadspace is seen in patients placed in the 20- 

degree Trendelenburg position. The arterial–to–end-tidal CO 2 

(PaCO 2 

-PETCO 2 

) gradient is increased compared with that in the 

supine posture. 33 Changes of intrapulmonary gas and pulmonary 

blood distribution are probably responsible for the observed 

physiologic deadspace and CO 2 

gradient differences. A study of 

10 anesthetized-paralyzed children aged 1 to 15 years undergoing 

laparoscopic surgery found that head-down tilt induced a mean 

decrease of 17% in lung compliance, which was further decreased 

by 27% from the baseline during intra-abdominal CO 2 

insuffla - 

tion. There is a concomitant increase in the peak inspiratory 

pressure (PIP) by 19% and 32% during Trendelenburg position 

and peritoneal insufflation, respectively. The changes in the lung 

compliance and PIP returned to their respective baseline values 

after removal of CO 2 

from the peritoneal cavity and the patient 

was returned to the supine position. 34 Respiration should be 

controlled when the child is placed in the head-down tilt because 

the work of breathing during spontaneous breathing is expected to 

increase and the reduction in lung volumes will predispose the 

lungs to atelectasis. This is more evident in the smaller child. The 

main contributing forces associated with negative intrapleural 

pressure are generated by the diaphragmatic and abdominal 

muscles. The hydrostatic pressure exerted by the abdominal 

contents on the diaphragm will hinder the motion and result in a 

greater work of breathing. In addition, in the neonate and infant, 

the increased compliance of the chest wall lowers the resting lung 

volume, making the FRC more difficult to maintain. The closing 

volume is also much higher in neonates and infants than in adults 

because of the decrease in elastic tissues. A spontaneous breathing 

technique in an anesthetized infant produces shunting and 

hypoxemia because the reduction in lung volumes will result in 

tidal breaths that are less than the closing volumes and, hence, 

alveoli closure developed. Pediatric patients should have their lung 

ventilation controlled in the head-down position to ensure opti - 

mal oxygenation and gas exchange. Data collected in a retros - 

pective audit of members of the French Association of Paediatric 

Anaesthetists (ADARPEF) revealed a high PETCO 2 

in 37% of 

neonates and children younger than 4 months and hypoxemia in 

0.5% when lung insufflation pressure was limited to 15 mmHg. 35 

Pulmonary mechanics in infants change significantly during 

laparoscopic CO 2 

pneumoperitoneum. The magnitude of change 

correlates directly with intraperitoneal pressure. The majority of 

infants required at least one ventilatory intervention to restore 

baseline tidal volume and PETCO 2 

. 36 It is generally not recom - 

mended to exceed an intra-abdominal pressure of 6 to 10 mmHg 

in newborns and children less than 5 kg and an intra-abdominal 

pressure of 10 to 12 mmHg in infants heavier than 5 kg and older 

children. 36,37 

Cerebral perfusion may be affected as the central venous 

pressure (CVP) is increased because of the effects of gravity. The 

shift of cerebrospinal fluid cranially from the spinal canal further 

predisposes the patient to a raise in intracranial pressure. Healthy 

patients placed in a 30-degree Trendelenburg position do not 

experience any significant changes or only a slight decrease in the 

middle cerebral arterial flow despite a reduction in the cerebral 

perfusion pressure (CPP). This decrease in CPP is probably the 

result of a decrease in cardiac output and MAP with an increased 

in the CVP. As long as blood pressure was maintained, cerebral 

autoregulation was intact and cerebral oxygenation preserved. 38 

The increase in the IJV pressure that occurred with the head-down 

tilt was transient, lasting less than 10 minutes. 34 Although the 

slight reduction in cerebral perfusion and the transient cerebral 

venous pooling should not produce any adverse effect on the 

cerebral circulation in patients with normal cerebral autoregula - 

tion, patients with intracranial pathology may experienced intra - 

cranial hypertension. The changes in intracranial pressure (ICP) 

that resulted from a head-down tilt of 45 degrees in anesthetizedparalyzed 

rabbits were nearly 200% and immediate on adoption of 

the steep Trendelenburg position. 39 The presence of hypotension, 

inadvertent or deliberate, with the head-down tilt should be 

considered risky for any patient because the CPP may be lowered 

significantly below the autoregulation limits and result in cerebral 

ischemia. Any other process that increases intrathoracic pressure 

such as the use of overzealous ventilatory maneuvers (e.g., PEEP) 

will also increases cerebral venous pooling and can lead to cerebral 

edema. 

Complications of the Head-Down Tilt 

Regurgitation or vomiting and subsequent aspiration of gastric 

contents remains an important cause of morbidity and mortality 

in anesthesia. It is generally accepted that the integrity of the lower 

esophageal sphincter is the major protective mechanism against 

regurgitation. The tendency to regurgitate is opposed by the 

barrier pressure between the lower esophageal and the gastric 

pressures. The effects of a 15- and 30-degree head-down tilt of 

healthy patients under general anesthesia have been shown to 

increase both gastric and lower esophageal pressures so that 

barrier pressure did not change significantly. The use of the 

Trendelenburg position does not predispose to gastroesophageal 

regurgitation. 40 However, patients with a history of gastroeso - 

phageal reflux may be at higher risk for regurgitation when they 

are placed in the Trendelenburg position. Animal studies showed 

that pigs with low esophageal sphincter pressure before induction 

of anesthesia regurgitated when placed in the head-down tilt with 

a pneumoperitoneum of 15 mmHg. 41 

Brachial plexus injuries (0.16% incidence rate) have been 

reported with the use of shoulder braces when the patient’s arm 

was extended at 90 degree. 42 Stretching or compression of the 

retroclavicular neurovascular bundle is believed to be responsible 

for the neurologic deficits. The recommendations of the depart - 

ment of anesthesiology of the University of California San Diego 

to avoid anesthesia-related neuropathies from the Trendelenburg 

position are (1) steep Trendelenburg position should be avoided 

whenever possible, (2) shoulder restraints, when necessary, should 

be placed over the acromioclavicular joints bilaterally, (3) abduction 

of the upper extremities should be less than 90 degrees from 

the body, (4) the patient’s head position should remain neutral, 

and (5) when the arms are abducted, the shoulder restraints 

should be removed on the ipsilateral side. 43 

Leg supports used during head-down tilt plus lithotomy 

posture should be adequately padded to prevent pressure on the 

common peroneal nerve. Once the position is finalized, the 

position of the tracheal tube should be reconfirmed to avoid


bronchial intubation because of the cephalad shift of the 

mediastinum and the upward displacement of the lungs and the 

carina. The risk of malposition of the tracheal tube in the pediatric 

patient is higher than in adults because the distance between the 

vocal cords and the carina is shorter. Even simple neck flexion and 

extension is known to result in a significant shift of the tracheal 

tube that could lead to bronchial intubation or inadvertent 

extubation. Increased CVP, intraocular pressure (IOP), and ICPs 

may be precipitated by steep Trendelenburg position. Clinical 

swelling of the face, eyelids and conjunctivae, and tongue has been 

observed, along with a plethoric color of venous stasis in the head 

and neck. Lingual and buccal nerve neuropathy can occur. In 

patients with substantial swelling, it may be prudent to delay 

removal of the endotracheal tube until that situation has improved 

to avoid the risks of upper airway edema. 44 There are no data 

demonstrating a higher incidence of unexpected neurologic events 

in patients placed in the steep Trendelenburg position for long 

operations, but there is one case report of a patient who had a 

cerebral hemorrhage during such a procedure and emerged with 

a significant neurologic deficit. 45 

LATERAL DECUBITUS POSITION 


The lateral decubitus position is inherently unstable and support 

must be available to maintain the patient in this posture. As the 

torso is tilted slightly laterally, usually a pad is placed under the 

shoulder so that the head and neck can be turned without tension. 

Such turning of the shoulder area alone may place torque on the 

lower back. It may be useful to place a pad under the hip so that it 

can follow the tilt of the shoulder and prevent the torque on the 

spine. Extreme lateral neck flexion has been reported to cause 

transient Horner’s syndrome. 46 Stability of the patient can be 

maintained by the use of straps, belts, or strips of adhesive tapes. 

Depending on the clinical circumstances, two straps are recom - 

mended with the upper applied just caudad to the axilla, taking 

care to avoid compression of the brachial neurovascular bundle, 

and the lower strap placed across the hip just below the iliac crests. 

They must be placed in such a manner that respiratory movements 

of the chest are not restricted and the abdomen moves freely to 

minimize respiratory compromise. Maintenance of the head and 

neck in a neutral position relative to the torso with pillows and 

support is also vital to avoid stretch injuries to the brachial plexus. 

The downside arm is usually tucked beneath the pillow that 

supports the head. An axillary roll placed just caudad to the axilla 

minimizes compression of the dependent neurovascular struc - 

tures. This minimizes the risk of brachial plexus injury due to 

compression of the nerves between the humeral head and the 

thoracic cage. There is a possibility of direct compression of the 

brachial plexus by an axilla roll when it is placed in the axilla, and 

care should be taken to ensure that the roll is placed beneath the 

upper chest. Other methods that have been used with success 

include the beanbag “Vacu-Pac.” This is a moldable support filled 

with thousands of tiny plastic beads. Once the patient adopts the 

necessary operative position, a negative pressure (e.g., vacuum) is 

used to remove all air within the Vacu-Pac through a valve. This 

process forces the beads tightly and molds the bag firmly around 

the contours of the patient, providing a support similar to a plaster 

cast. This device offers considerable advantages over the straps 

and padded rests in the pediatric patients. It has the added 

advantage of a more even distribution of the body weight and 

reduces the risk of pressure injuries. 

Once the lateral decubitus position has been established, the 

operating table is flexed at the level of or just cephalad to the iliac 

crest to establish the kidney position. Care must be taken not to 

raise the kidney rest (i.e., point of flexion of the table) within either 

the flank or the lower ribs of the patient (Figure 80–7). When 

placed correctly, little interference to the dependent lung and 

diaphragm is present and obstruction of the inferior vena cava is 

avoided. Because the legs will be in a dependent manner once the 

position is attained, elastic compressive stockings should be 

applied to minimize venous pooling. In the smaller child or infant, 

an appropriate-sized roll may be placed at the flexion point (Figure 

80–8). A modification of the lateral decubitus position is com - 

monly referred to as the left lateral or semiprone position. It is 

similar to the Sims position described by J. M. Sims in 1857. It may 

be used during gynecologic procedures and is commonly 

employed as a posture of recovery after anesthesia. The upside leg 

in the semiprone position is flexed at the knee and hip while the 

downside leg is kept extended. The body is allowed to rotate 

forward with gravity. The downside arm may be kept beneath the 

pillow supporting the head to facilitate breathing by extending the 

airway. 

Figure 80-7. The kidney position 

with the kidney resting beneath the 

down-side iliac crest to minimize interference 

of the downside diaphragmatic 

motion. The kidney rest, a 

transverse elevating bar of the table, 

is raised to increase the separation of 

the iliac crest from the lateral costal 

margin.


A 

Figure 80-8. A: Lateral decubitus in an infant with an axillary roll. B: Lateral decubitus in an infant with an axillary rolls. 

B 

Physiology of the Lateral Decubitus Position 

It was demonstrated that the upper airway of sedated, sponta - 

neously breathing children widens significantly in the lateral 

position compared with the supine position. This widening occur - 

red at all noncartilaginous areas of the upper airway and was most 

pronounced in the region at and below the tip of the epiglottis. 

The empirical findings confirm the widespread clinical experience 

that sedated children experience less upper airway obstruction in 

the lateral position than in the supine position. 47 A retrospective 

study of the hemodynamic and respiratory effect of pediatric 

urologic laparoscopic surgery 48 and another prospective study of 

the hemodynamic and respiratory effects of pediatric urologic 

retroperitoneal laparoscopic surgery 49 described the significant 

cardiopulmonary changes in children that were associated and 

occurred in relation to the CO2 insufflation in both retroperito - 

neal and transperitoneal approaches. The lateral position is well 

tolerated by most patients with minimal effects on the body. Few 

studies described the hemodynamic effects of postural changes 

from the supine to the lateral position. Changes will be more 

evident in exaggerated lateral positions with the kidney rest 

positions in which venous pooling in the dependent limbs is more 

significant. Venous return may also be reduced owing to kinking 

of the inferior vena cava. The proximity of the inferior vena cava 

to the right flank may allow compression by the kidney rest. It may 

result in a greater decrease in blood pressure than the left lateral 

position. Echocardiographic studies documented increases in 

right ventricular end-diastolic diameters in the left dependent 

position and shortened diameters in the right dependent position. 

The better preload and cardiac function in the left decubitus 

position is supported by the significantly increased in atrial 

natriuretic peptide levels compared with the supine. The right 

ventricular end-diastolic volume decreased by almost 10% in the 

right decubitus position and was associated with decreased atrial 

natriuretic peptide levels even though cardiac indices were 

unchanged. 

Like all other postures, postural-related mechanical restriction 

of chest movement limits lung expansion and results in reduction 

of lung volumes. In healthy conscious subjects, the vital capacity 

in the lateral position is decreased by 10% when compared with 

the sitting position. A greater reduction is seen with the use of the 

kidney position in which the truncal flexion can produce up to 

15% reduction in vital capacity. The reduction is due to the 

restriction of the thoracic cage movements and impairment of the 

ipsilateral hemidiaphragmatic motion. The tidal volume can be 

reduced up to 14%. In conscious adult subjects, a decrease of 

almost 16% in the FRC was observed when the subjects were 

placed in the lateral position from the sitting posture. This reduc - 

tion is almost of the same magnitude as in the prone position but 

is less than the decrease in FRC in the supine position (28%). 

Radiographic studies showed that the dependent lung is subjected 

to the compressive effects of the cranial shift of the lower 

hemidiaphragm whereas the nondependent diaphragm may not 

move cephalad at all. The smaller reduction in FRC may be due to 

the change in position of only one diaphragm (dependent lung). 3 

Similar changes were seen in the pediatric population. The FRC in 

supine anesthetized mechanically ventilated children was about 

60% of predicted awake value and increased by 19% when the 

child was turned to the right lateral decubitus posture. 50 In a group 

of anesthetized adult patients receiving mechanical ventilation in 

the lateral position, 34% of ventilation was distributed to the 

dependent and 66% to the nondependent lung. 51 The dynamic 

lung compliance and deadspace are lower and lung resistance is 

higher in the dependent versus the nondependent lung. Total lung 

dynamic compliance is, however, reduced, and the reduction 

occurred whether respiration was controlled or spontaneous. 52 

The decrease is progressive and probably due to the formation of 

atelectasis in the dependent lung and overdistention of the 

nondependent lung. Unlike in adults, ventilation is preferentially 

distributed to the uppermost lung in the lateral position in infants 

and young children—a reversal of the adult pattern. 53 The pattern 

of regional ventilation in children was examined using krypton- 

81m radionuclide ventilation lung scans in the supine, right, and 

left decubitus postures in 43 children aged 2 to 10 years. 54 The 

mean fractional ventilation to the right lung was 46% in the supine 

position, and this fell to 36% when dependent and rose to 56% in 

the nondependent position. Redistribution of ventilation away 

from the dependent toward the uppermost lung was seen in all 

children. In children aged 10 to 18 years, the mean fractional 

ventilation to the right lung was 57% (supine), 48% (dependent), 

and 63% (nondependent). These changes could be due to the 

difference in pleural pressure, which is closer to atmospheric


pressure in the infant, predisposing to closure of peripheral air - 

ways in the dependent regions of the lungs, because such ven - 

tilation is distributed toward the nondependent lung. In addition, 

there is likely to be less difference in contractility between depen - 

dent and nondependent hemidiaphragms in the young because 

the abdomen is narrower. Hence, because the abdominal-related 

preload is similar, there is less discrepancy in the fractional 

ventilation between the lungs. 

Complications Associated With the 

Lateral Decubitus Position 

Care must be taken to ensure that the down ear is positioned 

properly to avoid prolonged compression and pressure necrosis. 

The downside eye is at risk of compression and retinal artery 

thrombosis if positioned against an improperly placed headrest. 

Proper soft padding and great attention should be used to prevent 

this injury to the downside eye, ear, and facial nerve. The skin 

overlying the bony prominences of the lower limbs, especially 

on the downside leg, is at risk from pressure necrosis during 

pro longed positioning. Adequate padding should be provided 

underneath the patient and between the legs. The head and neck 

should be adequately elevated on a support in the neutral position 

to avoid stress and strain of the muscles that may result in 

postoperative neckache. Significant displacement of the tracheal 

tube caused by flexion and extension of the neck was shown using 

fiberoptic bronchoscopy in children between the ages of 16 and 

19 months. The tip of the tube moved a mean distance of 0.9 cm 

toward the carina with neck flexion and 1.7 cm toward the vocal 

cords with extension. Bronchial intubation and accidental extuba - 

tion could occur after significant changes of the head position in 

small children. 55 The same effect was observed with a nasally 

placed tracheal tube. 56 Unlike most surgical positions in which 

stretch injuries account for the majority of damage to the brachial 

plexus, compression is the principal cause of positional nerve 

injuries in the lateral position. This may occur when the lower 

shoulder and arm lie under the chest and compress the axilla in the 

lateral position without the use of an axilla roll. Conversely, an 

improperly placed roll may compress the axilla. A cervical rib may 

also predispose the brachial plexus to compression injury. 

Excessive stretching may lead to brachial plexus injury of the 

upside arm when there is excessive lateral flexion of the neck. This 

occurs more often because of postural instability secondary to 

surgical manipulations during the procedure. 

The suprascapular nerve may be stretched circumduction of 

the arm across the chest when the laterally placed patient is shifted 

to the semisupine position. This same injury to the nerve of lower 

arm occurs when the laterally placed patient shifts to the 

semiprone position and traps the arm beneath the chest. The long 

thoracic nerve may be injured when the head and neck of the 

patient are laterally flexed from the upper shoulder. The common 

peroneal nerve is one of the most frequent nerve injuries in 

patients placed in the lateral position. Compression of the nerve at 

the tip of the fibula happens when the patient is positioned with 

inadequate padding between the side of the leg and the operating 

table. The lower sciatic nerve may be compressed between the 

operating table and the ischiopubic ramus, whereas the upper 

sciatic nerve may be compressed by the retaining straps placed 

across the hips. 

When switching from two-lung to one-lung ventilation (OLV) 

during surgical thoracotomy, shunt fraction increases, oxygena - 

tion is impaired, and hypoxemia may occur. Hypoxemia during 

OLV may be predicted from measurements of lung function, 

distribution of perfusion between the lungs, whether the right or 

the left lung is ventilated, and whether the operation will be 

performed in the supine or the lateral decubitus position. Hypo - 

xemia during OLV may be prevented by applying a ventila tion 

strategy that limits alveolar collapse while minimally affecting 

perfusion of the dependent lung. The choice of anesthesia does 

not influence oxygenation during clinical OLV. Hypoxemia during 

OLV may be treated symptomatically by increasing inspired 

fraction of inspired oxygen, changing ventilation parameters, or 

using continuous positive airway pressure in the nonventilated 

lung. Hypoxemia during OLV may be treated causally by correct - 

ing the position of the double-lumen tube, clearing the main 

bronchi of the ventilated lung from secretions, and improving the 

ventilation strategy. 57 The lateral decubitus position has been 

reported to be associated with myonecrosis and sciatic nerve palsy 

but not compartment syndrome. 58 

PRONE POSITION 

General Considerations and Variations 

There are a number of variations of the prone position (Figure 

80–9). They include the horizontal prone, the head-elevated prone 

(Concorde position), the sea lion prone, the thoracic prone, the 

prone jack-knife, and the seated prone. The common element is a 

facedown patient with supports placed beneath the shoulders and 

the iliac crests, allowing freedom of abdominal movement and 

chest expansion. Since the 1950s, various methods of supporting 

the patient in the prone position have been described to reduce 

compression of the abdomen and enhanced respiratory function 

and cardiovascular stability. A great number of frames have been 

designed and an assortment of supportive devices and equipment 

has been used for protection of the head and relief of ventral 

abdominal pressure. The head is usually placed in a headrest or 

turned on the side while resting on a pillow. A padded foam or 

jelly donut shape can be used to protect the ear and the eye. 

Most often in pediatric anesthesia, surgical sheets rolled tightly 

to form a wrinkle-free cylinder is a simple and inexpensive 

Figure 80-9. Patient in the prone position shows the placement 

of rolls underneath the pelvis and the chest that allow proper 

abdominal expansion during mechanical ventilation. The head 

is turned on the side and leveled to maintain the cervical spine 

in line with the back. The eye and nose are padded to prevent 

injury, and the airway equipment is visible at all time and easily 

accessible. The feet are protected using a roll underneath the 

ankles.


90 degrees and the weight is borne on knees, and the pelvis is 

supported under iliac crests and pillows under chest. The arms are 

abducted above head and the head is turned to the side. The tight 

paraspinal muscles in the Georgia prone position can limit the 

lateral access to the spine. The Buie position is similar to the 

Georgia prone, but involves a head-down tilt and is useful for 

anorectal surgery. A hypobaric spinal block is possible. The Ray 

frame assumes a similar position but with more even weight 

distribution on the knees and the arms adducted across the chest. 

The seated prone position is also known to the knee-chest position. 

It has the advantage that the weight is borne on the ischeal tubero - 

sities and not the knees. 59 

Figure 80-10. The Wilson frame for spine surgery. Note the 

position of the pelvic and chest bolsters allowing complete 

clearance of the abdomen and proper mechanical ventilation. 

It is very important to ensure that all pressure points are wellpadded 

(see elbow). 

method of providing support for the torso, lifting the abdomen 

free from the surface of the operating table, and stabilizing the 

patient. For larger patients and/or specific surgical procedures, the 

Wilson, Relton-Hall, and Andrew frames can be used. The Wilson 

frame consists of parallel convex padded arches that allow a 

variable degree of adjustable curvature and is used to minimize 

the patient’s lumbar lordosis during spinal operations (Figure 

80–10). This frame supports both the iliac crests and the chest but 

is more suitable for adults or larger children undergoing lumbar or 

thoracic spinal procedures. The main advantages of this frame are 

that the abdomen and lower chest are unrestricted and that good 

surgical access to the intervertebral space may be achieved by 

adjusting the width and height of the frame. The Relton-Hall 

frame consists of four pedestals that could be adjusted to the 

dimensions of the patient. The padded pedestals support the 

patient just below the axilla on the anterolateral chest wall and at 

the anterior iliac spines (Figure 80–11). Although the chest and 

abdomen move freely, the whole weight of the torso is supported 

only at these four points and may result in the development of 

pressure sores, especially if the pedestals are inadequately padded. 

Finally, the Andrew frame is a kneeling system in which the weight 

of the patient is maintained on a chest support and on the knees. 

In this widely used version, longitudinal padded rolls support the 

torso with the chest resting on a chest pad. The hips are flexed at 

right angles and the knees rest on a kneeling pad. A gluteal pad 

helps to retain the flexion posture. 

Other variations include the Georgia position, in which 

the patient is kneeling on a shelf, her or his hips are flexed at 

Preanesthetic Evaluation 

If the prone position is required, a history of neck injury, cervical 

arthritis, or previous operations on the cervical spine should be 

documented and the range of movement of the head and neck 

assessed. Certain pediatric syndromes (e.g., Down and Morquio- 

Brailsford syndromes) are associated with cervical spine ano - 

malies, and such patients are at risk of cervical spinal cord injury. 

Stability of the cervical spine should be assessed and deficits 

documented in the preoperative assessment. The presence of a 

cervical rib should be excluded, because this will predispose to 

brachial plexus injury if the arms are to be abducted during 

surgery. The presence of obesity should be noted, because chest 

size may impose a shifting base, preventing a stable posture, and 

may also cause abdominal compression, so alternative frame 

devices that minimize abdominal pressure may be used or a 

variation of the prone position be employed. All limb movement 

should be tested. The elbows, arms, and legs must be able to flex 

and the arms must be lifted above the head without resulting in 

any injury. 

Physiology of the Prone Position 

Under normal circumstances in the awake state, diaphragmatic 

excursion increases intra-abdominal pressure while decreasing 

intrathoracic pressure. This pressure gradient facilitates venous 

return to the heart. Limitation of the diaphragmatic motion or 

institution of intermittent positive-pressure ventilation hinders 

venous return and, consequently, affects the cardiac output. Dimi - 

nished venous return may also occur with compression of the 

inferior vena cava and femoral veins by improperly placed sup - 

ports or via the effects of gravity. When they are compressed or 

the abdominal expansion is limited, the blood flow from the distal 

part of the body will be diverted into the perivertebral venous 

Figure 80-11. The Relton-Hall frame is 

an adjustable four-pedestal bolsters that 

allow control of the degree of lumbar 

lordosis by the varying the position of 

the pedestals.


plexuses (i.e., Batson’s veins). These are valveless and represent a 

very low pressure system. This may result in engorgement of the 

vertebral venous plexus during spinal surgery, contributing to 

increased blood loss. The correlation between the types of prone 

support and the inferior vena caval pressure was discussed. 60 A 

significant reduction of almost 50% in the mean inferior vena 

caval pressure was seen when the patient was positioned on a 

Relton-Hall frame compared with the prone position on a 

conventional pad. The association between an elevated CVP and 

an increased intraoperative blood loss was studied; however, the 

authors did not find any evidence to support the hypothesis that 

CVP is useful in determining the ideal prone position in patients 

undergoing lumbar laminectomy. 61 Patients undergoing halothane 

anesthesia and muscle paralysis positioned in a flat prone position 

did not show any significant changes in hemodynamic variables. 

However, the elevation of the frame led to a significant reduction 

in cardiac output (20%) and stroke volume with increases in 

peripheral vascular resistance. The decrease in cardiac output is 

believed to be secondary to the reduced venous return. 62 A study 

on the cardiovascular effects of four other different prone 

positions (patient on pillows, evacuatable mattress, Relton-Hall 

props, knee-chest/seated prone) found that the use of pillows (one 

underneath the thorax and another under the pelvis) resulted in 

less impairment than when the volunteers were prone in either the 

knee-chest position or in the Relton-Hall frame. 63 It has been 

suggested that the decrease in cardiac index could be attributed 

to increased intrathoracic pressures causing a decrease in arterial 

filling, leading to an increase in sympathetic activity via the baro - 

ceptor reflex. Consistent with this theory is the work that demon - 

strated decreased stroke volume accompanied by an increased 

sympathetic activity (increased heart rate, total peripheral vascular 

resistance, and plasma noradrenaline) in prone patients. Another 

study has suggested that, in addition to reduced venous return, 

left ventricular compliance may also decrease secondary to in - 

creased intrathoracic pressure that could contribute to the 

observed decrease in cardiac output. 64 

Recent investigations suggest that the anesthetic technique 

could affect hemodynamic variables in the prone position. 64-65 One 

study compared total intravenous anesthesia (TIVA) with 

inhalation anesthesia by measuring MAP and heart rate in patients 

undergoing spinal surgery. A greater decrease in arterial pressure 

in the TIVA group was observed. 64 The other study comparing 

inhalation anesthesia to TIVA for the maintenance of anesthesia 

used noninvasive cardiac output measures with the patients supine 

and then prone on a Montreal mattress. The authors found a 

decrease in cardiac index and increase in systemic vascular resis - 

tance on turning the patient prone. 65 The changes were greater 

during TIVA (decrease in cardiac index of 25.9%) than during 

inhalation anesthesia (12.9%). However, a contributor to these 

observations could be a change in propofol pharmacokinetics in 

the prone position. Measured propofol concentrations have been 

observed to increase during target-controlled infusions when 

patients are transferred from supine to prone, probably as a result 

of the decrease in cardiac output. 65 

Interference with rib cage and diaphragmatic movements may 

account for the reduction in vital capacity and tidal volume when 

patients are placed prone. Compared with the sitting position, the 

FRC in the prone position is reduced by 10%. Similar to the awake 

state, the reduction of the FRC in anesthetized-paralyzed patients 

in the prone position is of a smaller magnitude than that seen in 

the supine position. 66 Pulmonary airway resistance increased and 

compliance decreased in awake subjects when they were changed 

from sitting to the prone position. 67 Although pulmonary shunting 

was unchanged in anesthetized patients placed in the prone 

position compared with baseline awake values, 68 an increased 

gradient in the PaCO 2 

-PETCO 2 

gradient was observed. 69 A number 

of studies have shown that prone positioning improves arterial 

oxygenation. This improvement in oxygenation is well docu - 

mented in both adult and pediatric patients with acute respiratory 

diseases 70–72 as well as in patients receiving general anesthesia in 

the prone position. Several mechanisms have been proposed to 

explain this phenomenon and include an increase in lung volume 

(such as FRC) and an improvement in V˙/Q˙ matching. The latter 

can result from redistribution of perfusion to better-ventilated 

alveoli units or redistribution of ventilation to better-perfused 

capillaries. An increase in regional lung ventilation by recruitment 

of previously collapsed lung units with unchanged perfusion may 

also led to the improved oxygenation. An improvement in the V˙/Q˙ 

relationship with increases in ventilation, and a nongravitational 

distribution of perfusion to the nondependent lung regions in the 

prone position may also explain the improvement in oxygena - 

tion. 73,74 The latter is postulated to be related to regional differences 

in pulmonary vascular resistance (PVR) and not due solely to 

gravity. There is some evidence that PVR is intrinsically lower in 

the dorsal lung regions such that a more uniform distribution of 

blood is expected in the prone position. 75 Data on pulmonary 

mechanics in the pediatric patients placed in the prone position 

during anesthesia are still lacking. Using the inert gas argon 

rebreathing method adapted for neonates to measure FRC, no 

difference in FRC was observed in nonanesthetized babies studied 

in either the prone, the supine, or the right decubitus position. 76 

The effects of prone position in pulmonary mechanics in spon - 

taneously breathing healthy preterm infants aged almost 32 weeks’ 

gestational age were studied and showed that respiratory rate, tidal 

volume, minute ventilation, pulmonary resistance, or dynamic 

compliance was similar between supine and prone positions. 77 

Position-dependent cerebral ischemia may result from flow 

impairment in the large neck vessels (carotid and vertebral 

arteries) on marked movements of head and neck. In infants, 

extreme extension or rotation of the head, which may occur in the 

prone-sleeping position, can occlude one or both vertebral arteries 

and may be an important risk factor in some cases of sudden 

unexpected infant deaths. Rotation of the head is not uncommon 

when positioning the patient in the prone position and may 

predispose the brainstem to ischemia if the vertebral arteries are 

occluded. The risk of position-dependent cerebral hypoxemia was 

greatest with rotation of the neck and dorsal flexion of the head. 

No vertebral artery compression was demonstrated in the necks 

held in the neutral position. 78 The lag in available blood flow from 

small communicating and asymmetrical vertebral arteries may 

predispose the infant brainstem to ischemia if one or both ver - 

tebral arteries are occluded by head rotation or extension. 79 A 

patient with unrecognized carotid stenosis who suffered a fatal 

stroke after spine surgery positioned prone with the head rotated 

has been reported. 80 Occlusion of the vertebral arteries has been 

reported in at least four cases. In one, an underlying asymptomatic 

stenosis of the distal right vertebral artery led to hypoperfusion in 

those areas of the brain supplied after rotation or extension of the 

neck. 81 The patient developed a lateral medullary syndrome im - 

mediately after surgery but, with anticoagulation and rehabili - 

tation, made a good recovery. The other three case reports 

in volved patients with apparently normal vascular anatomy.


Complications of Prone Positioning 

Many injuries can occur when the patient is turned into the prone 

position. A survey of the process of transferring patients to and 

from the operating table showed that all anesthesiologists ques - 

tioned had no relevant training with regards to the transfer of 

patients. It was also reported that most transfers were undertaken 

by two staff alone. Injuries resulting from manual handling are 

common and operating theater staff should receive appropriate 

training. 82 The airway must be secured before positioning. 

Unintentional tracheal extubation while a patient is turned from 

supine to prone is a true risk. Monitoring cables as well as infusion 

lines should be placed so they do not become entangled upon 

turning the patient. Usually, disconnection is most convenient and 

may help to avoid severe complications. Intravascular access such 

as invasive arterial and central venous lines should be handled 

with great precaution before and during turning to prevent 

accidental dislodgment. The arms of the patients should be placed 

alongside the body during positioning, left in this position or 

abducted for the final positioning. The majority of skin contacts, 

the knees, iliac crests, elbows, can be at risk for pressure necrosis 

if the patient is left in this posture for long periods. A pillow or 

soft padding may be placed under these areas. Special attention to 

female breasts and particularly the nipples is necessary to prevent 

compressive necrosis and pain in the postoperative period. The 

eyes should be firmly taped after instillation of saline or an oph - 

thalmic lubricant to prevent corneal abrasions. Corneal abrasion 

presents immediately after emergence from anesthesia with severe 

pain in the eye. Conjunctival and periorbital injuries are frequent 

complications of the dependent eye. Other ophthalmic injuries are 

fortunately rare. They may be evident immediately after the 

surgery or occur several days after. 83 Retinal ischemia leading to 

blindness cannot be underestimated and is a potential complica - 

tion. The most common reported cause of postoperative visual 

loss is ischemic optic neuropathy (ION). 84 It is usually associated 

with hypotension and anemia. Fat or air embolism is a potential 

etiologic factor. In the older population, arteriosclerotic risk 

factors such as hypertension, diabetes, and smoking are important 

risk factors. 85 The perfusion pressure of the optic nerve head is 

determined by the difference between the perfusion pressure of 

the posterior ciliary artery and the IOP. Factors that decrease the 

posterior ciliary arterial pressure such as prolonged systemic 

hypotension or an increase in the IOP will decrease perfusion 

pressure and increase the risk of ION. A prolonged prone position 

with the head in a dependent, down-tilt position can be associated 

with a decrease in venous return leading to an elevation in local 

capillary bed stasis. As a result of increased CVP or venous 

obstruction, the IOP is raised with a corresponding decrease in 

choroidal blood flow, which leads to ION. 86 An appropriate 

headrest may minimize the risk of ocular complications. The 

weight of the head should be supported by the bony parts of the 

face and ear (i.e., forehead and zygomatic arches). Special attention 

should be provided to the position of the eyes and the nose of the 

patient. They should be positioned within the concavity of the 

frame or bolster. The head should be in the neutral position as 

much as possible to avoid rotation of the neck and potential 

vascular compression. Most important, whatever head and face 

support is chosen, repeated and careful inspection of the patient’s 

face should be done throughout the operative period to avoid this 

serious complication. Weight-bearing directly onto the face or 

forehead can hyperextend the neck and cause myofascial pain in 

the postoperative period. Macroglossia is a rare and unusual 

complication that has been described after posterior fossa surgery 

in the prone position. 87 It is probably the result of vascular 

congestion due to extreme flexion of the neck. Nerve injuries in 

pediatric patients represent 1% of all pediatric claims. 88 Peripheral 

nerve injury account for 16% of all claims in anesthesia. 11 Entrain - 

ment of air into the cranial cavity is common after neurosurgical 

procedures and occurs in all operative positions. There is a single 

case report of quadriplegia as a result of pneumorrhachis (air 

entrainment into the spinal canal) after posterior fossa explora - 

tion. 89 This was assumed to have resulted from a head-down 

position, allowing entrapped air in the posterior fossa to pass 

through the foramen magnum. Supportive treatment led to com - 

plete resolution of the symptoms. Excessive neck flexion in a 

patient undergoing an 8.5-h operation in the prone position with 

the neck flexed and the chin approximately one finger-breadth 

from the sternum resulted in complete and permanent C5–6 

sensory and motor deficit level after operation. This was presumed 

to result from overstretching of the cervical cord in a narrow spinal 

canal and a bulging C5–6 disk, with consequent ischemia. 90 

Although rare, space-occupying lesions within the spinal canal 

or cranial cavity can become symptomatic as a result of prone 

positioning, including spinal arachnoid cysts, 91 spinal metastases, 

and frontal lobe tumors. In each case, the mechanism involved was 

uncertain but the temporal relationship to the prone position 

strongly implicates it. Altered cerebrospinal flow dynamics and 

epidural venous engorgement could have been responsible. A 

patient with neurofibromatosis has also been described in whom an 

undiagnosed pedunculated neurofibroma in the posterior fossa fell 

anteriorly when prone, compressing the medulla and pons and 

leading to a bradycardia and fatal neurogenic pulmonary edema. 92,93 

Other less frequent complications include direct pressure 

necrosis of the skin in areas of iliac crest, chin, eyelids, nose, malar 

region, and tongue. 59 Contact dermatitis of the face from a head 

prone position and from the electrodes of a bispectral index on 

the forehead has also been reported. 94,95 Tracheal compression 

have been reported in a few cases due to reduced anteroposterior 

diameter of the chest and compression of the trachea between the 

sternum and the spine. This occurred in patients with thoracic 

scoliosis and was exacerbated by connective tissue defect of the 

trachea because of either Marfan syndrome or tracheomalacia. 96,97 

Submandibular gland swelling is also a reported complication 

most probably due to stretch of the salivary duct or venous stasis. 98 

Anterior shoulder dislocation when the arms are abducted at 90 

degrees at the shoulder in prone position has also been reported. 99 

The chest is usually large enough and strong to allow the 

patient’s weight to rest on it; however, in the presence of chest wall 

congenital deformities or after cardiothoracic surgery, reduction of 

the anteroposterior diameter of the chest can occur, leading to loss 

of the cardiac output probably due to compression of the heart 

and major vessels. 100 This can even be more pronounced in pectus 

excavatum. Two cases reported severe hypotension in prone posi - 

tion due to compression of the right ventricle against an abnormal 

sternum. 101,102 Another case report documented the compression 

of a Rastelli conduit in a patient with Fallot’s tetralogy during 

surgical manipulation of the spine. 103 

Abdominal organ compression may lead to hepatic ischemia, 

infarction, progressive metabolic acidosis, and elevated liver enzy - 

mes. 102,104 Pancreatitis is a known complication of spine sur gery 

related to systemic factors such as blood loss, hypotension, drug 

effect, or the use of CellSavers, as well as to prone posi tioning. 105


Limb compartmental syndrome and rhabdomyolysis were 

reported in the knee-chest position and other variations of the 

prone position involving flexion of the knees and hip joints, 

ranging from biochemical muscle damage evidenced by elevated 

plasma creatine phosphokinase to myoglobinemia and myoglo - 

binuria up to acute renal failure. Some patients required fascioto - 

mies. Care should be taken to avoid obstruction to blood flow in 

the lower limbs, which may lead to these ischemic complications. 59 

Venous gas embolism may occur owing to abdominal compres - 

sion of the inferior vena cava rendering a negative pressure 

gradient between the right atrium and the veins in the operative 

site. There is a variability in the sensitivity of the different detec - 

tion methods, and there is no formal evidence to support the 

insertion of a multiorificed central venous catheter as a means of 

aspiration of air emboli. 106,107 Fat embolism has also been reported 

during spinal surgeries. 

Prone Positioning and Resuscitation 

There are several reports for the management of cardiac arrest in 

the prone positioning. Conventional teaching has been that, in the 

event of the occurrence of life-threatening effects, the patient 

should be turned to the supine position; this has the advantages in 

terms of accessibility of the airway and pericordium and familia - 

rity. This necessitates the routine presence of a stretcher and the 

operating room table, so that the patient can be returned supine in 

case of problems during positioning. However, this may not be the 

case in some situations when there are bulky surgical instruments 

protruding from the back of the patient. Several techniques have 

been described in these situations. Chest compressions have been 

delivered successfully with the hands on the central upper back, 

between the scapulae. In some patients, it has been found neces - 

sary to provide counterpressure between the chest and the 

operating table to effectively compress the thoracic cage. Both onehanded 

and two-handed maneuvers have been described, as have 

a variety of hand positions to avoid open operative sites. 108 In one 

patient with an unstable spine, internal cardiac massage was 

undertaken via a left thoracotomy incision. 109 A “postcordial 

thump” delivered between the shoulder blades to treat pulseless 

ventricular tachycardia has also been described. 110 Defibrillation 

has been successfully undertaken using the anteroposterior paddle 

position 111 or paddle orientation on left and right sides of the 

back. 112 However, the use of posterior paddle positions may not 

deliver energy to sufficient myocardium, owing to anterior dis - 

placement of the heart in the prone position and also increased 

transthoracic impedance with positive-pressure ventilation. 113 The 

authors recommend the use of biphasic shocks and anterior 

paddle or pad positioning. It has also been recommended that selfadhesive 

pads be placed before prone positioning of the high-risk 

patient. 109 Rarely, the prone position may even benefit the patient 

needing resuscitation in which mediastinal masses compress the 

trachea or obstruct cardiac filling in the supine position. 114 

LITHOTOMY POSITION 


Lithotomy, for extraction of a bladder stone, was a common pro - 

cedure in the 16th century. This was performed with the patient 

sitting upright, legs abducted and flexed at the knees and res - 

trained by attendants. This seated posture is known as the “litho - 

A 

B 

Figure 80-12. A: Lithotomy position in a child using stirrups. 

B: Lithotomy position in a child using a “ring circle” mounted 

frame. 

tomy” position. In more recent times, however, the lithotomy 

position describes a patient in a supine position with the legs 

elevated and the knees flexed and held in position by supports 

(Figure 80–12). Several types of lithotomy positions are in use, 

and they differ mainly in the degree of leg elevation, the amount 

of abduction of the thighs, and the use of a head-down tilt. For 

the traditional lithotomy position, considerations in the pediatric 

population are similar to those of adult patients. The foot section 

of the operating table is usually removed and the leg holders are 

securely fixed to both sides of the table. As the patient is moved 

toward the end of the table to adopt the lithotomy position after 

induction of anesthesia, an adequate length of anesthetic breathing 

circuit and monitoring cables should be available. The hips of the 

patient should be positioned adjacent to the lithotomy supports 

and the legs abducted, knees flexed, and elevated to the degree 

appropriate for the surgical procedure. The arms of the patients 

should be flexed across the chest, or more commonly in the larger 

patient, supported by lateral armboards by the side of the operat - 

ing table. A sacral support with a wedge of a roll may be used to 

improve exposure of the perineum. 

In the pediatric patient, the final position will be determined 

by the type of leg support available. The availability of appr - 

opriately sized leg holders usually decides how the legs are being 

held up. Regardless of the type used, the legs must rest in a neutral 

position without strain or pressure on any joint. For the very young 

child, none of the conventional leg holders may be suitable and 

im provised supports such as sheet rolls may be used to hold the 

legs up. For the bigger child, a variety of leg holders for the 

lithotomy position is available. Each is connected to the pole that 

has been clamped to the side of the table. The legs are either held 

up by the ankles (“candy cane” pole, foot boot) or supported at the


popliteal fossa (“knee crutch”) or at the calf (“calf support”). The 

stirrups must be positioned according to the height, weight, and 

age of the patient and the estimate of knee-to-ankle and thigh 

lengths. One must note that the use of a leg support that leads to 

compression of the calves may predispose the patient to the 

development of compartment syndrome, especially if the patient 

is retained in the lithotomy position for a prolonged period. 

Although no particular type (skids, stirrups, boots) is exempted 

from the development of this complication, the use of stirrups is 

recommended because the support pressure is concentrated at the 

heel. Circumferential bindings to secure the legs in place or 

wrappings to prevent venous blood pooling are potentially harmful 

and are never recommended. 

Physiology of the Lithotomy Position 

Elevation of the legs increases venous return to the heart and 

activates baroreceptors to accommodate the volume shift via 

vasodilatation. There is a transient increase in the filling pressures 

of the heart, cardiac output, and cerebral arterial flow. Normal 

cardiovascular compensatory mechanisms tend to return the 

hemodynamic parameters to normal levels rapidly in healthy 

patients. The lithotomy position is known to decrease lower limb 

blood flow. There is a significant reduction in lower leg perfusion 

from 103 mmHg to 21 mmHg after 25 minutes in the lithotomy 

position. It is associated with a reduction in medial gastrocnemius 

muscle oxygen saturation from 68% to 58%. 115 The low lithotomy 

position resulted in a reduction of about 16% in lower leg systolic 

pressures, whereas an exaggerated lithotomy positions was 

associated with a decrease of almost 40% in lower leg pressures 

when compared with the supine data. When a 15-degree headdown 

tilt is added, the decrease in lower leg pressures was more 

significant. 116 MAPs of this level have been associated with the 

development of compartment syndromes, especially in patients 

who are in the lithotomy positions for 5 hours or more. In 

addition, these changes would be exacerbated in patients with 

peripheral vessel diseases flow, provoked ischemia in the lower 

limbs, and predisposed to lower extremity venous thrombosis. 

The lithotomy position limits respiratory movements by 

compression of abdominal viscera. It reduces the vital capacity of 

normal conscious patients by 18% as a result of the marked 

restriction of abdominal movement. The FRC and tidal volume are, 

however, minimally affected in the awake patient. However, it is 

suggested that raising the legs appeared to have little impact on 

respiratory elastance and resistances. 15 During spontaneous res - 

piration in anesthetized patients placed in the lithotomy position, 

a 3% reduction in tidal volume was seen and a 10-degree headdown 

tilt led to a 14% decrease. 50 Patients placed in the flexed headdown 

position, compared with the supine position, developed a 

significant decrease in arterial oxygen tension (14%) and a signi - 

ficant increase in CO 2 

tension (23%) and shunt fraction (78%). 117 

Complications Associated With 

the Lithotomy Position 

Although several complications have been reported, including 

finger burn, low back pain (14%) postoperatively, 118 and rhabdo - 

myolysis and elevated creatine kinase due to compression of calf 

muscles and ischemia, 119 none of these is known to have happened 

in children. Compartmental syndrome, a rare but life-threatening 

complication, particularly with head-down tilt (Lloyd Davies 

position) was reported after a lengthy procedure in the pediatric 

age group due to hypoperfusion and external compression by leg 

supports. 120,121 By placing the child in the lithotomy position only 

when access to the lower abdomen and perineum is required, 

these injuries may be avoided. For a lengthy procedure, using a leg 

support that places pressure on the popliteal fossa or the calf 

should be avoided. Systemic hypotension should be avoided and 

the risk posed by vasoconstrictive agents that decrease peripheral 

blood flow should be kept in mind. If needed, a clinical diagnosis 

can be obtained by venogram and magnetic resonance imaging 

(MRI). The venogram will demonstrate an external compression 

of the popliteal vein and the MRI an extensive muscle edema. 

Fasciotomies are necessary to relieve the compartment syndrome, 

whereas adequate rehydration and alkalinization of urine are 

cornerstones for the management of acute renal failure. 

Persistent neuropathies have been reported with an incidence 

of 1 per 3608 anesthetic instillations in a general surgical popula - 

tion. 122 Thin patients with a body mass index of less than 20, 

diabetes mellitus, and peripheral vascular disease in smokers 

predispose the patients to the development of lower limb neuropa - 

thies. Prolonged procedures (>4 h) are a definite association. Each 

hour in a lithotomy position increases the risk of motor neuro - 

pathy 100-fold. 122 This finding suggested that alternatives should 

be sought when a prolonged surgery in the lithotomy is planned. 

Forty percent of isolated sciatic neuropathies are associated with 

operation using the lithotomy position. Unlike compartment 

syndrome in which a prolonged duration in the lithotomy position 

is a significant risk factor, sciatic nerve injuries may occur even 

after short procedures. 123 The mechanisms for the development of 

neurapraxia include ischemic changes from a compartment 

syndrome or a direct compression of the nerve. 120 The sciatic nerve 

may be subjected to excessive stretching forces. The common 

peroneal nerve and its distal branches are the most common major 

motor nerve in the lower extremities to be affected by the litho - 

tomy position. 122 The common peroneal nerve may be compressed 

against the upright pole of stirrups as it passes around the head of 

the fibula when the legs are placed inside the poles. It is important 

also to remember that external pressure exerted by the surgical 

assistant leaning against the knees could contribute to this 

problem. The saphenous nerve may be compressed against the 

stirrups poles as it courses superficially near the medial malleolus 

when the legs are placed outside the poles. Femoral neuropathy 

have been reported and is thought to result from the extreme 

abduction of the thighs with external rotation at the hip causing 

ischemia of the femoral nerve as it is kinked beneath the tough 

inguinal ligament. 

To prevent lower back injury, the lower limbs should be moved 

simultaneously and symmetrically. The lower back should be 

supported to maintain the normal lumbar lordosis. Hip disloca - 

tion may follow slippage or disconnection of lithotomy poles. 

Lowering of the legs at the end of the surgery may be followed by 

hypotension secondary to hypovolemia. Accidental entrapment 

of the digits when lowering or raising the end of the operating 

table can cause crush injury, amputation, or skin breakdown. 121 

SITTING POSITION 


The use of the sitting position has decreased over the years. 

A postal survey of the use of the sitting position in general


neuro surgical practice in Britain was conducted in 1991. Com - 

pared with the data from 1981, the number of neurosurgical 

centers using the sitting position for posterior fossa surgery and 

posterior cervical spine surgery decreased more than 50%. 124 The 

surgical position is said to offer surgical advantages such as better 

surgical exposure; less tissue traction; less bleeding; less cranial 

nerve damage; more complete resection of the lesion; ready access 

to the airway, chest, and extremities; and presence of monitoring 

methods for early detection of venous air embolism (VAE). 

Neurosurgical practice in Germany, however, retained the sitting 

position as the preferred position for posterior fossa and cranio - 

spinal surgery, although the prone position is an alternative for 

use during posterior cervical surgery. Alternative positions like 

the lateral or the “park-bench” positions are rarely used. 125 The low 

sitting position offers main advantages over the sitting position by 

reducing venous pooling in the dependent areas as well as a 

reduced risk of VAE. The torso is usually placed in the midline of 

the operating table and the back section of the table is elevated. 

The hips and knees are flexed to provide some stability. The 

operating table is adjusted until the lower limbs are at the level of 

the heart. Pads are placed beneath the knees, as in the sitting 

position, to relieve ligamentous stress. The head-elevated prone 

position is mainly used during proce dures on the posterior cranial 

fossa or the cervical spine. Venous congestion at the operative site 

is minimal with gravity drainage. The arms of the patient are 

usually placed alongside the torso. Because the operative site is 

above the level of the heart, air embolism is a significant risk and 

appropriate monitoring should be instituted. 

There are several relative contraindications to the sitting position 

such as ventriculoatrial shunt in place and open, cerebral 

ischemia upright awake, left atrial pressure more than right atrial 

pressure, platypnea-orthodeoxia, and preoperative demonstration 

of patent foramen ovale or right-to-left shunt. If a shunt tube is in 

place from the cerebral ventricular system to the right atrium, air 

may enter the end of the shunt as cerebrospinal fluid drains out 

and may be pulled into the heart. The noncollapsible tubing acts 

as a noncollapsible vein and allows air to pass unimpeded into the 

heart. This is not a potential problem with a ventriculoperitoneal 

shunt, because the air would have no venous access. We recom - 

mend that a patient with a ventriculoatrial shunt in place have the 

shunt tied off before undergoing an intracranial procedure in the 

sitting position. Some patients experience cerebral ischemia 

whenever they assume the upright position. Their cardiovascular 

and cerebrovascular systems may both be implicated in this situa - 

tion. These patients may present for an extracranial-intracranial 

bypass for the posterior cerebral circulation; some surgeons 

believe that the sitting position gives the best exposure for this 

procedure. We cannot be sure that cerebral circulation will be 

maintained in the sitting position, because we must not only place 

the patient upright but also provide an anesthetic. It seems a 

reasonable balance of risks and benefits to place such a patient in 

the horizontal position. There has been suggested that, if the left 

atrial pressure, as measured by pulmonary artery occlusion 

pressure, is less than the right atrial pressure in the sitting position, 

the patient should be placed horizontally because of an increased 

risk of paradoxical embolism. 126 This is based on two important 

assumptions: (1) the left atrial pressure will be greater than the 

right atrial pressure in the horizontal position and (2) the atrial 

pressure gradient and its direction constitute a prognostic 

indicator of whether VAE will become paradoxical air embolism 

(PAE). Some work suggests that these assumptions may not be 

applicable. In a pig model with an iatrogenic atrial septal defect, 

the atrial pressure gradient before air embolism was unrelated to 

the occurrence of PAE. 127 We believe that decisions regarding the 

use of the sitting position based on estimates of preoperative atrial 

pressure gradients are not well founded. Some patients demon - 

strate a potential right-to-left shunt before surgery. Platypnea/ 

orthodeoxia is an unusual cardiovascular illness in which the atrial 

gradients apparently reverse when the upright position is assum - 

ed. 128 Patients with this condition are well oxygenated in the supine 

position but become easily desaturated in the upright position 

because of unsaturated blood passing from right to left at the atrial 

level. Other patients demonstrate a patent foramen ovale before 

surgery during a cardiac work-up, and still others may have a 

known right-to-left shunt. These patients might be at greater risk 

for PAE should VAE occur; therefore, it seems prudent to give 

these findings appropriate consideration before using the sitting 

position for such patients. 

Physiology of the Sitting Position 

Of all the surgical positions commonly used, the effects of gravity 

on the cardiovascular system are most evident in the sitting posi - 

tion. The magnitude of the hemodynamic changes will be depen - 

dent upon the type of sitting position adopted and influenced by 

the anesthetic agents employed. The gravitational effects will have 

the most significant impact in the full sitting position with a 

straight back and legs dependent; this posture is, fortunately, rarely 

used nowadays. Modifications in which the legs and thighs are 

flexed and the feet are at the level of the heart will have less signi - 

ficant hemodynamic effects. Different anesthetics with their dif - 

ferent pharmacologic effects may affect the hemodynamics 

differently. The incidence of hypotension in anesthetized patients 

in the sitting position varies from 5% to more than 30%. The 

incidence and extent of hypotension in the sitting position are 

influenced by the technique of patient positioning, the use of 

equipment such as elastic stocking wrapping or antigravity suits to 

minimize the effects of gravity on hemodynamics, the physical 

status of the patients studied, and the anesthetic techniques. 129 A 

significant decrease in the right atrial pressure from a mean of 3.4 

to 0.68 mmHg was observed in 60 anesthetized-paralyzed patients 

aged 2 to 13 years scheduled for neurosurgical procedures in the 

sitting position. Of these, 25% of patients had a subatmospheric 

right atrial pressure, although MAP was only slightly decreased. 129 

These results are consistent with the decrease in venous return to 

the heart and diminished filling of pulmonary vessels. These 

effects were expected to be more exaggerated in hypovolemic 

patients. 

With the patient breathing spontaneously, the sitting position 

caused the least physiologic changes in the respiratory system 

among all the positions described. Because the weight of the 

abdominal contents is not acting against the diaphragm in the 

sitting position, it offers the least restriction to movement of 

the diaphragmatic or chest wall and the least impairment of FRC. 

Lung volumes are preserved with increases in the FRC and closing 

volume from supine values. 130 The average lung compliance was 

greatest in patients in the sitting position, less in the lateral, and the 

least in the supine positions. The total respiratory resistance is 40 

to 50% less in the sitting position compared with supine values. 

Because of the effects of gravity on the pulmonary circulation, the 

upper lung fields are less well perfused. There is closure of alveolar 

and extra-alveolar vessels in the upper part of the lung in the


patients placed in the sitting position. The use of intermittent 

positive-pressure ventilation may further reduce blood flow to 

these areas. There is an increase in the nonuniformity of intra - 

pulmonary gas distribution in patients who are anesthetized and 

mechanically ventilated compared with awake values in the sitting 

position, 131 and this may lead to V˙/Q˙ mismatch. Volatile agents 

abolish the hypoxic pulmonary vasoconstriction responses and 

exacerbate the mismatch. The reduction in cardiac output in the 

upright posture also led to the significant decrease in arterial 

oxygenation. 132 These pulmonary effects is children are similar to 

those in adults. The effects of body positions on pulmonary 

mechanics were examined in 30 former preterm infants. 133 These 

infants were sedated and kept breathing spontaneously. Changing 

from a supine position to semisitting position at 45 degrees 

decreased total pulmonary resistance and augmented the specific 

and dynamic lung compliances and increased FRC. 

The neck and cerebral vessels above the level of the heart are 

subjected to reductions in intra-arterial and venous pressures in 

the sitting position because of gravitational forces. The subatmos - 

pheric pressure within the neck veins predisposes the patient to 

the risk of VAE. The relationship of superior sagittal sinus pressure 

(SSP) to head position during jugular venous compression and 

PEEP on SSP was examined in 15 children. 134 Progressive head 

elevation significantly decreased mean SSP, and in 5 patients, SSP 

was less than 0 mmHg at 90 degrees torso elevation. The applica - 

tion of 10 cmH 2 

O PEEP was ineffective in raising the SSP, whereas 

bilateral internal jugular compression always caused a significant 

increase in SSP. These observations suggest that children are at 

great risk for VAE when undergoing neurosurgical procedures in 

the sitting position because intracranial venous pressure is often 

subatmospheric when the head is elevated. 

A head-up position may have beneficial effects on ICP via 

changes in MAP, airway pressure, CVP, and cerebrospinal fluid 

displacement. A paradoxical increase of cerebrovascular tone and 

ICP may occur, however, when the head-up position is associated 

with a decrease in MAP through autoregulation mechanisms. This 

is mainly because of the compensatory increase in systemic 

vascular resistance in response to the reduction in systemic arterial 

pressure. When mechanical ventilation with PEEP is used in 

patients without intracranial hypertension, intracranial perfusion 

is unchanged. However, in patients with increased ICP, the 

combination of head flexion with application of PEEP may result 

in a dangerous increase in ICP, even when the patients were in the 

sitting position. 135 

Complications of the Sitting Position 

Hypotension is the most common complication of the sitting 

position. Measures to minimize hypotension include slow staged 

positioning over 10 to 20 minutes and adequate fluid loading. The 

use of compressive elastic bandages or stockings to wrap the lower 

limbs before elevating the patient may partially reduce the amount 

of blood pooled in the dependent structures. Treatment with 

vasopressors may be required in severe cases. Vital sign changes 

resulting from brain manipulation may also occur. Positioning the 

patient from supine to sitting is a common cause of tracheal tube 

malplacement in the pediatric patient because the distance be - 

tween the vocal cords and the carina is shorter than in the adult. 55 

It is not uncommon for the head to be flexed excessively in the 

sitting position to optimize surgical exposure; compression or 

kinking of the tracheal tube may result. A reinforced tube is 

recommended and there should be at least one fingerbreadth 

distance between the chin and the chest. The insertion of the 

transesophageal echocardiography or Doppler probe may lead to 

misplacement or compression of the tracheal tube. The major phy - 

siologic concern for patients in the sitting position is air entrain - 

ment when the surgical site is above the level of the heart, which 

may result in VAE (see Chapter 57). 

Peripheral nerve injuries reported with the sitting position are 

likely to be due to faulty positioning or prolonged surgery. Com - 

mon peroneal nerve injury is fortunately rare (incidence < 1%). 

However, sciatic nerve injury is more frequent as a result of 

compression or stretching. Other nerves injuries such as brachial 

plexus 136 and recurrent laryngeal nerve palsies have also been 

reported. 137 The latter was attributed to the large probes placed in 

conjunction with neck flexion and tracheal intubation. Quadri - 

plegia is rare and the result of prolonged stretching and compres - 

sion of the cervical cord from excessive head flexion, 138 PAE into 

the arterial system, and occlusion of the vertebral artery due to 

excessive neck flexion. Young patients exhibiting extraordinary 

growth spurts may demonstrate a higher risk for this complica - 

tion. Nitta and colleagues described a 7-year-old boy who develop - 

ed acute cervical spinal cord infarction after an operation in the 

sitting position. 138 It was assumed that head flexion and the 

presence of the abnormal skeletal growth spurt resulting from an 

excessive secretion of human chorionic gonadotropin from a 

tumor was a possible predisposing factor for this complication. 139 

Somatosensory evoked potential monitoring has been proposed 

as an indicator of the adequacy of regional spinal cord perfusion 

in cases requiring sitting position during surgery. 

Macroglossia may result in either inadequate positioning of the 

head or excessive oral cavity manipulation. Extreme flexion of the 

head with the chin resting on the chest and the prolonged use of 

an oral airway may promote obstruction of venous and lymphatic 

drainage of the tongue after procedures performed in the sitting 

position. Postoperative macroglossia may lead to airway obstruc - 

tion. It is recommended that any oral airway should not be left in 

the oral cavity and a bite block used instead. 

Deep venous thrombosis is frequent during prolonged surgery, 

especially if associated with intraoperative hypotension. In larger 

patients, the use of sequential pneumatic compression devices 

should be used to minimize this risk. 

Blindness is an unusual complication that may result from 

direct compression of the eye. Pediatric patients, especially new - 

borns and infants, are at higher risk because the horseshoe 

headrest is often used and most often inappropriately sized for the 

zygomatic arches. Blindness may also result from an episode of air 

embolism involving the occipital cortex. 140 

PROLONGED BEDREST AND 

PATIENT TRANSPORT 

Prolonged bedrest may be responsible for most of the physiologic 

changes occurring with postural changes. A contraction of the 

plasma and blood volume (10–16%) as well as altered vasomotor 

responses have been observed after 2 to 6 weeks with 6-degree mild 

head-down bedrest. The latter is probably due to the inhi bition of 

the synthesis and release of norepinephrine. These changes lead to 

orthostatic intolerance with a decrease in blood pressure when 

these subjects are seated upright. 141 A down-regula tion of the 

cardiovascular oxygen transport system is seen after prolonged 

bedrest. Stroke volume, cardiac output, and hemoglo bin level are


lowered after an enforced period of inactivity. This is accompanied 

by a decreased in oxygen delivery up to 40% at rest whereas oxygen 

consumption is reduced by almost 16%. 142 A similar reduction of 

13% in maximal oxygen consumption was reported in children 

aged 7 to 11 years after 9 weeks of bedrest for various illnesses. 143 

Prolonged bedrest produces profound changes in muscle and bone, 

particularly of the lower limbs. Dramatic change in muscle mass 

occurs within 4 to 6 weeks of bedrest, which is associated with 

a reduction in muscle strength of 40%. Even in young students, 

10 days of bedrest led to decreases in muscle strength and mass. 

Isometric muscle strength was de creased in both nonantigravity 

and antigravity muscles, although the rate of changes did not 

correlate with the corresponding changes in muscle mass. A 

reduction in neuromuscular function probably contributed to the 

decreases in maximum voluntary strength, 144 whereas a decrease 

in muscle protein synthesis accounts for the decrease in both whole 

body and skeletal muscle mass. 145 Ideally, patients should be 

transferred in their bed from their ward to the operating theater. In 

patients who have been confined to bed for a prolonged period, 

the physiologic derange ments may provoke dizziness and nausea, 

possibly hypotension. All patients should be reviewed thoroughly 

before anesthesia induction because the potential complications 

that may arise from the transport-related instability are certainly 

preventable. Transfer of the patient onto the operating table should 

be done as gently as possible. Careful planning must be achieved 

before positioning. 

POSITIONING IN PARTICULAR CASES 

Experienced personnel should tailor the required and special 

consideration during positioning to each patient depending on 

the patient’s own medical condition, physical deformity, and 

surgical needs, avoiding anticipated complications that could 

happen such as compression injuries, hemodynamic effects, or 

respiratory problems. For example, placing neurologic patients 

with contracture deformities in the supine position is sometimes 

difficult or impossible. Care has to be taken not to overstretch the 

extremities in these situations, and the most appropriate position 

exposing the surgical field can be achieved by cooperation with 

surgeons and other personnel, to reach the optimum for the 

patient’s condition. For instance, patients suffering from osteo - 

genesis imperfecta, a group of connective tissue disorders, are 

characterized by very fragile bones that can fracture easily during 

positioning for surgery. Patients affected with severe scoliosis can 

render positioning difficult. Patients presenting with Down 

syndrome are another case in which special consideration must 

be taken during positioning. Occipitoatlantoaxial instability must 

be kept in mind to avoid subluxation or fracture of the cricoid 

apophysis, especially in prone position. Care should be taken to 

avoid forced extension and flexion by in-line stabilization by a 

skilled helper. 

CONCLUSION 

The reduction of potential morbidity associated with positioning 

of patients in the operating room begins with a well-conducted 

preoperative evaluation. Risk factors should be assessed while 

evaluating the range of movement, especially the joints most 

involved for the patient’s position during surgery. Obvious defor - 

mity should be assessed and the neurologic function documented. 

Adequate protection should be conferred to these during the 

operative procedure. Communication with surgical colleagues is 

of prime importance to determine the position ex pected for 

surgery; operating room personnel should be informed of the 

intention; and all proper equipment needed to achieve safe 

positioning of the patient should be readily available. Transfer of 

patients to the operating rooms should be a stress-free experience 

for all involved, and coordination between the transport and the 

operating staff should be discussed before beginning anesthesia. It 

is essential that all equipment be serviced regularly and rechecked 

before every use. Knowledgeable staff acquainted with the phy - 

siologic demands of specific positions should ideally be present 

during the positioning of the patient. Accurate intraoperative 

documentation is imperative once the patient has been positioned. 

Immediately after positioning, airway equipment, ventilation, and 

hemodynamic stability should be checked, and confirmation that 

everything is in order should be obtained confirmed before any - 

thing else is done to the patient. All monitoring devices, intra - 

vascular lines, and proper padding to avoid pressure point 

complications must be provided. Special attention to the face, eyes, 

neck, and neurovascular structures must be checked before the 

patient is covered with the surgical blankets. As much as correct 

positioning can effectively aid surgery, improper positioning 

should never be accepted because the consequences potentially 

resulting from any oversight can lead to permanent injuries and 

dramatic outcome for the patient, the family, and the professionals 

involved in his or her care. 

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