The laryngeal mask airway has been used for periods of up to 10–24 h with no apparent problems [1–3]. Uvular necrosis of unknown origin has been reported following tracheal intubation , but to our knowledge, there are no other reports of pharyngeal necrosis associated with airway management.
A 53-yr-old female (weight 110 kg, height 163 cm) was scheduled for elective clipping of her left anterior cerebral communicating artery following a grade III subarachnoid haemorrhage. The patient was not considered to be at risk of aspiration. The airway was maintained with fibreoptic-guided intubation through a size 5 laryngeal mask airway under general anaesthesia using a size 7.5 mm endotracheal tube to minimize the cardiovascular stress response to laryngoscopy. Insertion of the laryngeal mask airway was easy and the cuff was inflated with 20 mL air. Fibreoptic intubation was accomplished at the first attempt. There was no significant change in heart rate or blood pressure (measurements 5% ± baseline) during laryngeal mask airway insertion or intubation. A 14-FG nasogastric tube was passed into the stomach blindly behind the mask to permit enteral nutrition. The operation lasted for 8 h and the intraoperative course was unremarkable. Postoperatively, the patient was transferred to the intensive care unit for elective ventilation of the lungs. The laryngeal mask airway was left in situ since it was felt that attempts to remove it around the tracheal tube might result in accidental extubation or stimulation of the cardiovascular system jeopardizing the newly clipped aneurysm. Similarly, the cuff was not deflated since it was felt that the deflated cuff would make the position of the mask unstable and be more likely to cause movement of the endotracheal tube and stimulate the cardiovascular system. It was considered that the patient would probably be extubated within 48 h, but neurological function was slow to return and extubation and removal of the laryngeal mask airway did not take place until the eighth postoperative day. Shortly after extubation the patient developed acute respiratory distress and required reintubation. An area of necrosis, 0.75 cm in diameter, was seen at laryngoscopy in the midline on the posterior pharyngeal wall. This was treated with corticosteroids and debridement via a fibreoptic scope for one week. The patient subsequently recovered from respiratory failure and the pharynx healed completely. There were no further sequelae.
Animal studies have shown that tracheal mucosal injury is primarily related to the pressure exerted against the mucosa and, to a lesser extent, the duration of application of that pressure. There are no published data about the relationship between pharyngeal mucosal injury and the level/duration of mucosal pressure, but there is evidence that pharyngolaryngeal morbidity with the laryngeal mask airway is more common at high volumes  and following prolonged insertion . The mean mucosal pressure exerted by the laryngeal mask airway is lower than the capillary perfusion pressure, but can occasionally exceed it at high cuff volumes, particularly against the posterior pharynx. Mucosal pressures may have been higher in our patient for several reasons: (a) the cuff was not deflated; (b) a large mask was used; (c) the patient was obese (there is some evidence that obese patients have a smaller pharynx than non-obese patients); and (d) there was a nasogastric tube in situ that might have created an area of high pressure. There are a lack of data about the use of the laryngeal mask airway for prolonged periods although procedures lasting more than 2 h have been commonly performed, and it has been used in 15 patients for between 4 and 8 h without problems . There are two reports of laryngeal mask airway use in the intensive care unit for 10–24 h without apparent problems [1–3].
In retrospect, it would have been better to have removed the laryngeal mask since it is unlikely that accidental extubation would have occurred if an extender had been used and there is evidence that removal is unlikely to trigger a clinically significant cardiovascular stress response. Furthermore, the position of the laryngeal mask cuff is probably stable over the inflation range making it unnecessary to keep the cuff inflated. Unfortunately, this information was not available when the case occurred.
We conclude that there may be limits to the duration the laryngeal mask airway can be safely left in situ in terms of pharyngeal injury, particularly in the presence of a nasogastric tube. Animal studies are required to determine the extent of these limitations.
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