Trip Answers

Question answered:08/01/08 Warning! this question is over two years old.

Synopses

1. Because of their propensity for airway collapse and sleep deprivation, patients at increased perioperative risk from OSA are especially susceptible to the respiratory depressant and airway effects of sedatives, opioids, and inhaled anesthetics; therefore, in selecting intraoperative medications, the potential for postoperative respiratory compromise should be considered. For superficial procedures, one should consider the use of local anesthesia or peripheral nerve blocks, with or without moderate sedation. If moderate sedation is used, ventilation should be continuously monitored by capnography or another automated method if feasible because of the increased risk of undetected airway obstruction in these patients. One should consider administering CPAP or using an oral appliance during sedation to patients previously treated with these modalities. General anesthesia with a secure airway is preferable to deep sedation without a secure airway, particularly for procedures that may mechanically compromise the airway. Major conduction anesthesia (spinal/epidural) should be considered for peripheral procedures. Unless there is a medical or surgical contraindication, patients at increased perioperative risk from OSA should be extubated while awake. Full reversal of neuromuscular block should be verified before extubation. When possible, extubation and recovery should be carried out in the lateral, semiupright, or other nonsupine position.

2. Preoperative sedation with benzodiazepines 45 minutes before the induction of general anaesthesia has anticonvulsive and muscle relaxing effects on the upper airway musculature, causing an appreciable reduction of the pharyngeal space. Consequently, a higher risk of preoperative phases of hypopnoea and consecutive hypoxia and hypercapnia arises after administration, and oxygen saturation needs to be monitored adequately. An effective anxiolytic agent will reduce the dose of anaesthetic needed to induce general anaesthesia, which may otherwise lead to an increased likelihood of cardiovascular complications. If needed, oxygen can be given by an insufflation mask preoperatively, and application of nasal continuous positive airway pressure might be necessary postoperatively. The main goal in all patients is to avoid inadequate ventilation and oxygenation resulting in hypoxaemia or hypercapnia and any associated haemodynamic changes (such as tachycardia, arrhythmia, and hypertension) leading to increased morbidity and mortality. Death, brain injury, cardiopulmonary arrest, airway trauma, and damage to teeth are among the adverse events associated with difficult airway management. A difficult airway is defined as the clinical situation in which a conventionally trained anaesthetist experiences difficulties with ventilation of the upper airway by facemask, difficulty with tracheal intubation, or both. The purpose of the American Society of Anesthesiologists' guidelines is to reduce the likelihood of adverse outcomes by providing basic recommendations. The equipment for management of a difficult airway should be in place before induction of general anaesthesia. Orotracheal tubes in various sizes, as well as a McCoy laryngoscope and a fastrach laryngeal mask, are necessary. Fibreoptic devices may be helpful but have no impact in acute emergency situations. A strategy or algorithm for establishing a secure airway should be defined. 

Source: Evidence Direct http://www.mh.org.au/royal_melbourne_hospital/secure/downloadfile.asp?fileid=1016047

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