Chapter 86

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1458 PART 5 ■ Anesthetic, Surgical, and Interventional Procedures: Considerations reductions in cardiac output and blood pressure are likely to occur during the case. Ventilation during surgery can be achieved either by mechani - cal ventilation or by hand ventilation by the anesthesiologist. Even if mechanical ventilation is used, periods of manual ventilation are often necessary. PROBLEMS WITH GAS EXCHANGE: Insufflation of CO 2 com bined with a limited possibility to maintain adequate alveolar ventilation will result in serious CO 2 retention combined with pronounced respiratory acidosis (pH 7.0). This situation is further compounded by the fact that the measurement of end-tidal-CO 2 is notoriously unreliable and the CO 2 tracing may even become absent during parts of the procedure. A well-functioning arterial line is, thus, a prerequisite in this situation. Desaturation episodes can be considered the rule, and to counteract this as much as possible ventilation with 100% oxygen is recommended during the period of OLV. The combination of hypoxia, hypercapnea and acidosis will of cause add to the increase in pulmonary vascular resistance caused by the atelectasis of the right lung. Due to the substantial altera - tions that take place both regarding hemodynamics and gas exchange it is very useful to use cerebral near-infrared spectros - copy (Invos) to monitor cerebral oxygenation throughout the procedure. 182 Requirements for monitoring and vascular access are: 1. normal noninvasive monitoring 2. arterial line for repeated blood gas analysis and invasive blood pressure monitoring 3. at least two peripheral venous lines or if deemed necessary a femoral or central venous catheter 4. cerebral near-infrared spectroscopy (Invos) Even if it is clearly possible to perform TOF repair as a thora - coscopic procedure, the combination of neonatal anesthesia with periods of hypoxia, pronounced hypercarbia, and substantial acidosis may raise concern regarding the risk for brain cell apoptosis with potential long-term cognitive and behavioral problems (see “Effects of Anesthetic Agents on the Premature and Neonatal Brain” above). Despite this, there are case reports where this technique at least initially has been used successfully, even in TOF cases with significant concomitant congenital heart disease (e.g., pulmonary atresia with single ventricle physiology). 182 POSTOPERATIVE CARE Pain Scoring The use of appropriate pain scales for monitoring of postoperative pain is fundamental to the provision of optimal pain relief. Im plementation of regular pain assessment has a number of advan tages: 1. regular pain assessment and charting of the results increases the awareness of the care providers regarding the problem of postoperative pain in neonates and children 2. assessment performed before and after an intervention aimed at reducing pain will provide the care providers with feedback regarding the efficacy of the intervention 3. pain assessment will provide a tool for evaluation of different analgesic techniques and allows for a more structured and scientific analysis of the treatment of postoperative pain The problem with pain assessment in the neonatal period is that existing pain scales are only designed and validated for shortterm procedural pain (e.g., heel lancing). Frequently used pain scales which has been developed and validated for ongoing postoperative pain in neonates and infants are the CHIPPS scale 183 and the CRIES score. 184 An advantage with the CHIPPS scale is that the intention with this scale is not only to assess pain but also to identify a score which will predict the need for administration of supplemental analgesia. However, a recently published com - parison of neonatal pain scores did find that the neonatal infant pain scale may be a preferable pain evaluation tool in the setting of neonatal surgery. 185 Analgesia A plan for treatment of postoperative pain should be available in all neonates. The metabolism of paracetamol (acetaminophen) is reason ably well developed in the neonate and, thus, this drug should be regularly administered. Rectal dosages of 20 to 40 mg/kg have been reported to result in safe plasma concentrations in the preterm and term baby. 186,187 Whenever possible, regional anesthe - tic techniques should also be utilized due to the excellent quality of pain relief combined with the low risk for unwanted side effects. 188 If regional techniques are not applicable or are insuf - ficient, continuous low-dose infusions of opioids are often helpful (e.g., morphine 10–20 g/kg/h) 189 and with careful titration of the infusion the risk for respiratory depression is very small. However, more complicated analgesic regimens should be carried out under closed supervision in the NICU or high dependency unit. Fluid Balance/Nutrition If the neonate has been subjected to anything but a minor proce - dure or pure diagnostic examination, there will be a postsurgical stress reaction inducing a state of catabolism and fluid retention. Although the period of catabolism and fluid retention is shorter in newborns and infants it is not possible to resume full nutrition or normal fluid volumes immediately following surgery. Ignoring the effects of the postsurgical stress reaction will lead to unnecessary strain on the neonates metabolism and cardiorespiratory system and will also lead to unwanted fluid retention and edema. Thus, during the first 12 to 24 hours postoperatively it is generally wise to restrict the fluid volume to approximately 80 to 100 mL/kg 24 h and give only a glucose solution, for example, 10% glucose with sodium 40 mmol/L and potassium 20 mmol/L. Early supplementation with lipid emulsions can, however, be used in neonates requiring additional caloric support. 190 This traditional approach has recently been challenged by data showing that neonates undergoing major gastroschisis surgery are able to achieve a positive protein balance if given parenteral amino acids (2.5 g kg-1 24 h-1) immediately postoperatively without signs of protein intolerance. 191 However, further prospective randomized trials including the full variety of neonatal surgical procedures are needed before changing the more traditional approach described above. Antibiotics Although mainly a surgical concern the anesthesiologist should check that appropriate antibiotic coverage has been order for
CHAPTER 86 ■ Management of the Neonate: Anesthetic Considerations 1459 the patient. If not, or if any doubts exist regarding the need for or the choice of antibiotic, the anesthesiologist should contact the surgeon to discuss this matter. Radiographic Examinations A postoperative chest radiograph is frequently performed follow - ing a number of interventions in order to check for adequate line and tube placing and to rule out pneumothorax. Radiographic control of the location of epidural catheters should also be performed if the catheters have been threaded via the caudal or lumbar epidural route to a more cephalad position. The suspicion of partial intravenous injection through the epidural catheter also warrants postoperative radiographic control. The necessity for other investigations will have to be individualized and is most of the times the responsibility of the surgeon. Postoperative Complications Complications during the immediate postoperative period in neonates is dominated by ventilatory problems. The most common problems encountered are the following: opioid-induced hypoventilation, postoperative apnea in the ex-premature, residual muscle relaxation, postextubation stridor, inadequate ventilation due to insufficient pain relief, and upper airway obstruction. The frequency of these potentially life-threatening events merits close supervision of the neonate for at least 24 hours postoperatively before being returned to an ordinary ward. The anesthesiologist is often confronted with questions regard - ing postoperative diuresis. In this situation, it is important to remember that the normal newborn child does not always pass urine until 12 to 24 hours after birth and that the surgically induced stress response leads to water conservation and reduced diuresis. It is, thus, not reasonable to expect a hourly urine output in excess of about 1 mL/kg/h in the immediate postoperative phase. If the patient is believed to be truly oliguric, the anes - thesiologist has to decide whether this is due to hypovolemia or if diuresis should be enhanced by the administration of loop diuretics. It should be remembered that patients can be hypovole - mic despite showing signs of peripheral edema, for example, on the dorsum of the hand and feet and eye lids. Although postoperative hemorrhage is unusual following neonatal surgery, additional volume replacement is frequently necessary following major operations due to ongoing losses through drains or due to developing tissue edema and “third spacing.” If postoperative hemorrhage or hypovolemia of other causes do occur the clinical signs will be usual: diaphoresis, reduced peripheral circulation, prolonged capillary refill, tachycardia, oliguria, and hypotension. SPECIFIC NEONATAL CONDITIONS REQUIRING SURGICAL INTERVENTION Airway Obstruction Stridor A variety of different conditions can cause the presence of inspi - ratory stridor with jugular and intercostal/subcostal retractions in the neonate: 192 (1) bilateral choanal atresia, (2) Pierre–Robin syndrome, (3) cystic hygroma, (4) laryngomalacia, (5) laryngeal web or adhesion of the vocal cords, (6) vocal cord paralysis, (7) subglottic hemangiomas, (8) tracheomalacia. It should be remembered that in a significant number of neonates outside the immediate newborn, period the cause for the stridor can be ac - quired and, thus, a sequelae of previous intubation. 193 If the inspiratory stridor is more severe in nature or if it tends to be progressive causing respiratory distress the cause of the obstruc - tion needs to be clarified. In the case of bilateral choanal atresia, the diagnosis is made by trying to pass a suction catheter through each of the nostrils (see Chapter 63). In more severe cases of cystic hygroma, the condition will be obvious from observing the swelling in the neck. Apart from these conditions, a diagnostic bronchoscopy will have to be performed to identify the cause of the problem as well as determining the degree of obstruction. Depending on the finding made during the bronchoscopy further action may need to be undertaken (e.g., tracheal intubation or tracheotomy). How to approach this problem will obviously depend on the severity of the condition. If the stridor is only slight or moderate, a preoperative workup can be performed in a normal fashion, whereas if the symptoms are judged to be life-threatening, immediate action needs to be taken. It is of vital importance both for the well-being of the patient and for diagnostic purposes that spontaneous ventilation is preserved during the anesthetic. The main steps of anesthetic management are summarized in Table 86–14. Cleft Lip Repair Neonatal surgical intervention in these conditions is now perfor - med in certain centers in order to improve the cosmetic and functional outcome. 194 Cleft lip/palate can be associated with other malformations, but frequently patients are otherwise healthy and normal. The main steps of anesthetic management are sum - marized in Table 86–15. Thoracic Surgery Esophageal Atresia With Tracheoesophageal Fistula The incidence of the malformation is approximately 1/3000. The lesion is classified I to V depending on the anatomic configuration of the tracheoesophageal fistula. In the majority of cases the upper esophageal segment ends in a blind pouch with the lower esopha - geal segment connecting to the trachea close to the carina via a fistula. This abnormality makes the neonate unable to swallow its own pharyngeal secretions and the baby will cough or even choke when breastfed. More serious aspiration into the airways can also occur through the fistula, which is in direct continuum with the stomach. Acid aspiration of gastric secretions can cause significant chemical pneumonitis. In order to minimize the risks of pulmo - nary aspiration, surgery should be performed without undue delay. Surgery can be deferred until the next morning and since available expertise and infrastructure is usually superior during daytime this is often preferable compared to the on-call nighttime setting. The main steps of anesthetic management are summarized in Table 86–16. Tracheoesophageal Cleft Tracheoesophageal cleft is a very rare syndrome with an estimated incidence of approximately 1/100,000. The extent of the cleft
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Chapter 86

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