Hypotension during induction of anaesthesia is neither a reliable nor a useful quality measure for comparison of anaesthetists' performance

Background. Identification of statistically reliable outcomes for comparison among anaesthetists is challenging. Time-weighted intraoperative mean arterial pressure <65mmHg (AUC(65)) is associated with increased odds for myocardial damage. We explored retrospectively whether such hypotension before incision was statistically reliable for peer comparison. Methods. We retrieved electronic data between 2006 and 2015 at a tertiary care, academic hospital in the USA for patients at risk for myocardial damage (inpatient after surgery, ASA physical status >= III, >= 50 yr of age, and case duration >= 60 min). We determined the percentage of anaesthetists comparable based on caseload and case-mix. The AUC65 was compared amongst anaesthetists supervising >= 100 cases involving at-risk patients during the last 12 months. Results. Only 14.1% [95% confidence interval (CI) 13.6-14.5%] of cases involved patients who were 'at risk' during the 10 yr study period. A yearly average of 49 (SD 6) anaesthetists supervised >= 100 cases of any type, of whom only 52% (95% CI 47.1-56.0%) supervised >= 100 cases involving at-risk patients. Thus, nearly half the anaesthetists would have been excluded from peer comparison. During the last 12 months, there were two outliers among 34 evaluable anaesthetists (P<0.05, controlling for false discovery). However, their contribution to total hypotension amongst cases for all patients was small, because hypotension was widely distributed (e.g. 80% of hypotension attributable to 61.8% of anaesthetists, 95% CI 59.8-63.7%). There was no relationship between the AUC65 and propofol induction dose. Conclusions. The AUC65 of time-weighted pre-incision hypotension is not a suitable metric for comparing anaesthetists. There were few at-risk patients, half the anaesthetists were not evaluable because of their case-mix and caseload, and hypotension was widely distributed.