Download Update 11 - Update in Anaesthesia - WFSA

44Update in Anaesthesialoss. The wound site must also be observed every fewminutes to ensure that any bleeding or haematomaformation is noted early. Drainage from surgical drainsshould also be charted.Conscious level should be monitored by observing thereturn of reflexes such as the eyelash reflex, swallowingand the start of vocalisation and response to commands.Where the patient has undergone regional anaesthesia(spinal or epidural) the height of the block must be assesseduntil it is seen to be regressing. This is most easily testedby measuring the point at which cold can no longer beappreciated (using ethyl chloride or ice). It is safer not tosit these patients up too early as marked posturalhypotension can occur.Once the patient is vocalising and is reasonably awakepain levels should be assessed. Recovery nurses shouldbe capable of administering intravenous analgesia andachieving adequate analgesia should be a primary goal onceairway reflexes have returned. Pain is most easily treatedby administering morphine 1-2 mg aliquots every 3-5minutes until comfortable. It is very unusual to overdosepatients using this regime, but intravenous naloxone shouldbe available. See also Update in Anaesthesia 1997; 7.Supplemental oxygen therapyWhenever possible all patients recovering from anaesthesiashould be given supplemental oxygen (4l/min by face mask).Where facilities are limited, provided the airway andbreathing is monitored closely, young, fit individuals havingrelatively minor procedures can often recover withoutsupplemental oxygen. However it should be givenwhenever possible in the less fit population having majorsurgery. Anaesthesia, particularly halothane, obtunds, orin some cases abolishes, the hypoxic respiratory drive sothat hypoxia no longer stimulates increased ventilation.Coupled with this is a much increased tendency forhypoxaemia to occur due to a variety of reasons includingairway obstruction due to an obtunded conscious level,hypoventilation secondary to opioids and anaestheticagents, diffusional hypoxia caused by nitrous oxidediffusing into the lungs faster than nitrogen can diffuse inthe opposite direction and many different causes ofventilation/perfusion mismatching. These include atelectasis(absorption collapse, mucus trapping, prolongedhypoventilation), a decrease in functional residual capacitywith anaesthesia and supine posture, poor mucus clearance(absent/impaired cough reflex and poor ciliary function),and possibly hypovolaemia or pulmonary oedema. Patientsparticularly at risk of postoperative hypoxia include thosewho have received nitrous oxide or opioids, and thosewith pre-existing pulmonary disease. Where oxygen canbe administered, even 2 litres per minute via nasalspectacles or face mask may be sufficient to preventdesaturation associated with most of the causes listedabove. It is also important to realise that the tendency forhypoxaemia extends long into the postoperative periodand is particularly likely to occur on the first postoperativenight. If possible, high risk patients undergoing majorsurgery should receive supplemental oxygen for 48-72hours.Monitoring EquipmentThe most useful monitors in the recovery area are the pulseoximeter and the sphygmomanometer. The latter isobviously considerably cheaper, more widely available anddoesn’t need electricity to function. It provides valuableinformation about a patient’s cardiovascular status.Postoperatively patients are often mildly hypotensive dueto the sedative effects of drugs and the likelihood of bloodloss or intraoperative fluid redistribution (coupled withsome degree of dehydration due to preoperative fasting).More marked levels of hypotension (or even moreseriously a downward trend in blood pressure) often heraldan unrecognised blood loss, an adverse cardiac event ormay follow spinal anaesthesia. For these reasons it isprudent to monitor blood pressure every five minutes orso until it is stable and within normal limits. This alsodemonstrates why it is important to document the vitalsigns over a period of time, so that these trends can moreeasily be spotted and acted upon.Since its widespread introduction in the 1980’s the pulseoximeter has become one of the mainstays of postanaesthetic monitoring. Where available these machineswill give a fairly reliable indicator of systemic oxygenation,together with some indication of cardiovascular status.Oxygen saturation levels should remain above 93% anddesaturation below this level in recovery is most commonlycaused by airway obstruction and poor or inadequateventilation. The presence of a good quality pulsatile signalusually denotes adequate peripheral circulation, althoughvasodilatation and hypotension can still be present, so theblood pressure should still be monitored. See p11 forfurther reading regarding the use of pulse oximeters.Apart from the above minimal monitoring, furtherassessment must be tailored to a patient’s particular needs.Urine output should be assessed where an indwellingurinary catheter is sited and ECG monitoring may benecessary where a patient is at risk of arrhythmias.