Comparison between LMA-Classic and AMBU AuraOnce laryngeal mask airway in patients undergoing elective general anaesthesia with positive pressure ventilation.

BACKGROUND: The LMA-Classic laryngeal mask airway (Classic LMA) is an autoclavable and reusable laryngeal mask airway with strong evidence supporting its efficacy and safety. Due to the concern of infection risk particularly of prion disease, various single-use laryngeal mask devices were developed. The Ambu AuraOnce LMA (Ambu LMA) is a single use disposable laryngeal mask airway with special design that conforms better to the anatomy of the airway.

OBJECTIVES: The Ambu LMA was compared to the LMA-Classic Classic LMA in respect to ease of insertion, adequacy of seal intraoperatively and postoperative complications in patients undergoing elective general anaesthesia with positive pressure ventilation.

METHODS: One hundred and eighteen ASA I and II patients undergoing elective general anaesthesia were randomly allocated into receiving either the Ambu LMA or the Classic LMA. The time taken and number of attempts taken to insert the laryngeal mask was recorded. Intra-operative adequacy of seal was assessed via the amount of nitrous oxide leak using a nitrous oxide analyser. Readings were charted at 0, 20, 40 and 60 minutes of operation. Complications postoperatively (blood stains on the device and occurrence of sore throat) were also recorded.

RESULTS: The success of first attempt insertion was comparable between the two groups (Classic LMA 87% versus Ambu LMA 83%). However the time of insertion was significantly shorter in the Ambu LMA group (p = 0.008). Nitrous oxide level was comparable between the two groups up to 20 minutes of operation. At 40 and 60 minutes, the Ambu LMA showed a significant lower nitrous oxide leak compared to the Classic LMA. Postoperatively, incidence of blood stains was comparable between the two groups, however the incidence of sore throat was lower in the Ambu LMA group (p = 0.025).

CONCLUSIONS: This study demonstrated that the Ambu LMA was comparable to the Classic LMA in terms of the ease of insertion, but provided better seal during positive pressure ventilation with less postoperative sore throat.