Application of Minimum Effective Cuff Inflating Volume for Laryngeal Mask Airway and its Impact on Postoperative Pharyngeal Complications.

BACKGROUND: High intracuff pressure can cause severe pharyngeal complications including sore throat or hoarseness after laryngeal mask airway (LMA) removal postoperatively. Though the application of minimum effective cuff inflating volume is suggested to maintain airway sealing and adequacy of ventilation for patients receiving general anesthesia with LMA at lower level of the intracuff pressure, it is currently not a standard care in most of the anesthetic departments. In this study, the minimum effective cuff inflating volume was determined for classic LMA Well Lead™ (Well Lead Medical Co., Ltd., China) and its impact on postoperative pharyngeal complications was also explored.

METHODS: Patients with American Society of Anesthesiologists physical status (I-III) undergoing the short-duration urological surgery were recruited in this trial. First, the minimum effective cuff inflating volume was determined for size 4 or 5 LMA Well Lead in the study 1. Immediately following placement and confirmation of ideal LMA position, the cuff was inflated with 5, 7, 10 ml of air and up to 30 ml at 5 ml increment. The intracuff pressure, oropharyngeal leak pressure (OLP), and inspiratory peak airway pressure under positive pressure ventilation at the corresponding cuff volume as indicated above were recorded. Second, the enrolled patients were randomly allocated into minimum effective cuff inflating volume group (MC) and routine care (RC) group in the study 2. The minimum effective cuff inflating volume was applied and maintained in MC group, whereas the cuff volume was inflated with half of the maximum cuff inflating volume recommended by manufacturer in RC group throughout the surgical procedure and stay in postanesthesia care unit prior to LMA removal. The incidence of pharyngeal complications at 0, 2, 24, and 48 h after removal of LMA and other intra-operative adverse events were also documented.

RESULTS: The intracuff pressure varied with the cuff inflating volume in a positive linear correlation manner (Y = 11.68X - 42.1, r(2) = 0.9191) under the range of 5-30 ml for size 4 LMA. In similar with size 4 LMA, the data were also showed the linear relationship between the intracuff pressure and the cuff inflating volume (Y = 7.39X - 10.9, r(2) = 0.8855) for size 5 LMA. The minimal effective cuff inflating volume for size 4 or 5 LMA was 7-9 ml in combination of considering OLP needed to maintain airway sealing during intermittently positive pressure ventilation. The intracuff pressure in MC group was lower compared with RC group (63.0 ± 3.7 vs. 126.4 ± 24.0 cmH2O for size 4 LMA; 55.6 ± 2.4 vs. 138.5± 26.8 cmH2O for size 5 LMA; P < 0.0001). The incidence of pharyngeal adverse events was lower in MC group versus the RC group at 2, 24 h after LMA removal.

CONCLUSIONS: The relationship between the cuff inflating volume and the intracuff pressure for size 4 or 5 LMA Well Lead(TM) is in a linear correlation manner at the range of 5-30 ml. The minimal cuff inflating volume is adequate for satisfactory airway sealing and consequently associated with lower incidence of postoperative pharyngeal complications for LMA Well Lead.™.