Association of preoperative anaesthesia consultation prior to elective noncardiac surgery with patient and health system outcomes: a population-based study

Background: Surgical volumes and use of preoperative anaesthesia consultations are increasing. However, contemporary data estimating the association between preoperative anaesthesia consultation and patient (days alive and at home [DAH(30)], mortality) and system (costs, length of stay, and readmissions) outcomes are not available.Methods: We conducted a population-based comparative effectiveness study using linked health administrative data among patients aged >= 40 yr who underwent intermediate-risk to high-risk elective, inpatient, noncardiac surgery in Ontario, Canada (2009-17). Our primary outcome was DAH(30). Secondary outcomes included DAH(90), 30-day and 1-yr mortality, 30-day health system costs, length of index admission, and 30-day readmissions. Propensity score overlap weights were used to adjust for confounders. Prespecified effect modifier analyses focused on high-risk subgroups.Results: Among 364 149 patients, 274 365 (75.3%) received a preoperative anaesthesia consultation. No adjusted association was found (22.5 days vs 22.5 days; adjusted ratio of means 1.00, 95% CI 1.00-1.00) between consultation and DAH(30) in the full population. We identified significant effect modification (significantly more DAH(30)) among patients with ischaemic heart disease, ASA physical status >= 4, frailty index score >= 0.21, and who underwent vascular surgery. Secondary outcomes were associated with preoperative consultation, including greater DAH(90), decreased length of stay, lower 30-day and 1-yr mortality, and reduced 30-day costs.Conclusions: Preoperative anaesthesia consultation was not associated with greater DAH(30) across the overall study population. However, important potential benefits were observed among high-risk subgroups. Research is needed to identify optimal patient populations and consultation processes.