Provider variability in the intraoperative use of neuromuscular blocking agents: a retrospective multicentre cohort study

Objective: To assess variability in the intraoperative use of non-depolarising neuromuscular blocking agents (NMBAs) across individual anaesthesia providers, surgeons and hospitals.

Design: Retrospective observational cohort study.

Setting: Two major tertiary referral centres, Boston, Massachusetts, USA.

Participants: 265 537 adult participants undergoing non-cardiac surgery between October 2005 and September 2017.

Main outcome measures: We analysed the variances in NMBA use across 958 anaesthesia and 623 surgical providers, across anaesthesia provider types (anaesthesia residents, certified registered nurse anaesthetists, attendings) and across hospitals using multivariable-adjusted mixed effects logistic regression. Intraclass correlations (ICC) were calculated to further quantify the variability in NMBA use that was unexplained by other covariates. Procedure-specific subgroup analyses were performed.

Results: NMBAs were used in 183 242 (69%) surgical cases. Variances in NMBA use were significantly higher among individual surgeons than among anaesthesia providers (variance 1.32 (95% CI 1.06 to 1.60) vs 0.24 (95% CI 0.19 to 0.28), p<0.001). Procedure-specific subgroup analysis of hernia repairs, spine surgeries and mastectomies confirmed our findings: the total variance in NMBA use that was unexplained by the covariate model was higher for surgeons versus anaesthesia providers (ICC 37.0% vs 13.0%, 69.7% vs 25.5%, 69.8% vs 19.5%, respectively; p<0.001). Variances in NMBA use were also partially explained by the anaesthesia provider's hospital network (Massachusetts General Hospital: variance 0.35 (95% CI 0.27 to 0.43) vs Beth Israel Deaconess Medical Center: 0.15 (95% CI 0.12 to 0.19); p<0.001). Across provider types, surgeons showed the highest variance, and anaesthesia residents showed the lowest variance in NMBA use.

Conclusions: There is wide variability across individual surgeons and anaesthesia providers and institutions in the use of NMBAs, which could not sufficiently be explained by a large number of patient-related and procedure-related characteristics, but may instead be driven by preference. Surgeons may have a stronger influence on a key aspect of anaesthesia management than anticipated.