A randomised controlled trial of the effect of laryngeal mask airway manometry on postoperative sore throat in spontaneously breathing adult patients presenting for surgery at a university teaching hospital

Background: Laryngeal mask airways (LMAs) are widely used in anaesthesia and are considered to be generally safe. Postop- erative sore throat (POST) is a frequent complication following LMA use and can be very distressing to patients. The use of an LMA cuff pressure of between 30 and 32cm of H20 in alleviating post-operative sore throat has not been investigated.Objective: To compare the occurrence of POST between the intervention group in which LMA cuff pressures were adjusted to 30-32cm of H20 and the control group in which only monitoring of LMA cuff pressures was done, to compare the severity of POST between the two study groups and to compare the LMA cuff pressures between the two study groups.Methods: Eighty consenting adult patients scheduled to receive general anaesthesia with use of an LMA were randomized into two groups of 40 patients each. Intervention group: LMA airway cuff pressures were adjusted to 30 to 32cm of H20. Con- trol group: Only had LMA cuff pressures monitored throughout the surgery. All patients were interviewed postoperatively at two, six and twelve hours. Data of their baseline characteristics, occurrence and severity of POST was collected. If POST was present; a Numerical Rating Scale (NRS) was used to assess the severity. Cuff pressures between the two study groups were also determined.Results: The baseline demographic characteristics of the participants were similar. The use of manometry to limit LMA AMBU® AuraOnce™ intracuff pressure to 30-32cm H2O reduced POST in surgical patient’s by 62% at 2 hours and 6 hours (Risk Ratio 0.38 95%CI 0.21-0.69)in the intervention group. The median POST pain score in the intervention group was significantly lower than the control group with scores of 0 at 2, 6 and 12 hours post operatively. Routine practice of LMA cuff inflation by anes- thesiologists is variable, and the intracuff pressures in the control group were higher than in the intervention group. (P<0.001)Conclusion: Among this population, reduction of LMA AMBU® AuraOnce™ intracuff pressure to 30-32cm H2O reduces the occurrence and severity of POST. The LMA cuff pressures should be measured routinely using manometry and reducing the intracuff pressures to 30-32 cm of H20 recommended as best practice.Keywords: Laryngeal mask airway manometry, sore throat, surgery