Multicentre validation of manufacturers' weight-based recommendations for laryngeal mask airway size choice in anaesthetic practice: A retrospective analysis of 20,893 cases.

BACKGROUND: Manufacturers' weight-based recommendations for laryngeal mask airway (LMA) sizes are not scientifically founded and have never been validated clinically. OBJECTIVE: The validation of manufacturers' weight-based recommendations in clinical practice and whether other patient variables such as sex and age may influence LMA size choice. DESIGN: A retrospective study. SETTING: Four Israeli hospitals (two tertiary and two secondary hospitals). METHODS: Data on LMA use were retrieved from the Anaesthesia Information Management System (AIMS). Multinomial logistic regression analysis including weight, sex and age amongst adults, adolescents and children was used to identify predictors of LMA size used (development data set). Concordance between the size of LMA used and that predicted according to the model and the manufacturers' recommendations was assessed (validation data set). RESULTS: LMA insertions were analysed in 13,743 (65.8%) adults, 1807 (8.6%) adolescents and 5343 (25.6%) children. Suitability of manufacturers' recommendations was higher in children [4075/5343 (76.3%)] than adults [5200/13743 (37.8%)] or adolescents [885/1807 (49.0%); P < 0.001 for children vs. adults or adolescents]. Sex influenced LMA size in adults and adolescents, but not in children. Age had no influence. Amongst adults and adolescents, LMA size was better predicted by the regression model than by manufacturers' recommendations [adults: anaesthetists/model 61.7%, 95% confidence interval (95% CI) 60.1 to 63.2, anaesthetists/manufacturer 38.4%, 95% CI 36.0 to 39.0, P < 0.001; adolescents: anaesthetists/model 68.1%, 95% CI 64.1 to 72.0, anaesthetists/manufacturer 46.9%, 95% CI 42.7 to 51.1, P < 0.001]. In children, the regression model and manufacturers' weight-based recommendations performed equally (anaesthetists/model 78.0%, 95% CI 75.9 to 80.0, anaesthetists/manufacturer 75.7%, 95% CI 73.6 to 7.8, P = 0.126). CONCLUSION: Manufacturers' weight-based recommendations for LMA size reflect clinical practice in children, but not in adults and adolescents. In these age groups, choice of LMA size is influenced by sex and weight, although with wider ranges than those recommended by manufacturers.