Postoperative Residual Neuromuscular Blockade (rNMB) Following Low-Dose (<2×ED95) Atracurium in Patients Receiving Laryngeal Mask Airway - An Audit Study

Background: Low dose neuromuscular blockers, typically <2×ED95 or <0.46 mg/kg, have been shown to improve conditions of Laryngeal Mask Airway (LMA) placement and ease of ventilation during general anesthesia (GA), but its effects on the prevalence of residual neuromuscular blockage (rNMB) is poorly defined. A previous study in a large tertiary institution showed that 19% of patients undergoing GA with LMA received neuromuscular blockers. This study aims to audit the practice and establish the prevalence of rNMB. Methods: A cross-sectional, observational study was designed. Patients were included if they received a low dose of atracurium (<2×ED95). Quantitative neuromuscular monitoring with electromyography was performed on emergence upon removal of LMA (Train of Four ratio <0.9). Results: Two hundred patients were sampled randomly, 109 met the inclusion criteria. The overall prevalence of rNMB was 22.0% (average dose of atracurium (0.275 (± 0.093) mg/kg)). It was three times higher in patients who were not reversed (8.3% vs. 25.9%). The lack of use of reversal agents (OR 6.623, CI 0.030-0.771, p<0.05) and a shorter duration from the atracurium dose to emergence (OR 1.029, CI 0.956-0.988, p<0.05) were found to be associated with an increased risk of rNMB. Conclusion: Administering low-dose (<2×ED95) atracurium in patients receiving laryngeal mask airway still results in significant prevalence of residual neuromuscular blockade post-operatively. It is critical to monitor and reverse patients where appropriate.