Dose-Dependent Protective Effect of Inhalational Anesthetics Against Postoperative Respiratory Complications: A Prospective Analysis of Data on File from Three Hospitals in New England

Objectives: Inhalational anesthetics are bronchodilators with immunomodulatory effects. We sought to determine the effect of inhalational anesthetic dose on risk of severe postoperative respiratory complications. Design: Prospective analysis of data on file in surgical cases between January 2007 and December 2015. Setting: Massachusetts General Hospital (tertiary referral center) and two affiliated community hospitals. Patients: A total of 124,497 adult patients (105,267 in the study cohort and 19,230 in the validation cohort) undergoing noncardiac surgical procedures and requiring general anesthesia with endotracheal intubation. Interventions: Median effective dose equivalent of inhalational anesthetics during surgery (derived from mean end-tidal inhalational anesthetic concentrations). Measurements and Main Results: Postoperative respiratory complications occurred in 6,979 of 124,497 cases (5.61%). High inhalational anesthetic dose of 1.20 (1.13-1.30) (median [interquartile range])-fold median effective dose equivalent versus 0.57 (0.45-0.64)-fold median effective dose equivalent was associated with lower odds of postoperative respiratory complications (odds ratio, 0.59; 95% CI, 0.53-0.65; p < 0.001). Additionally, high inhalational anesthetic dose was associated with lower 30-day mortality and lower cost. Inhalational anesthetic dose increase and reduced risk of postoperative respiratory complications remained significant in sensitivity analyses stratified by preoperative and intraoperative risk factors. Conclusions: Intraoperative use of higher inhalational anesthetic doses is strongly associated with lower odds of postoperative respiratory complications, lower 30-day mortality, and lower cost of hospital care. The authors speculate based on these data that sedation with inhalational anesthetics outside of the operating room may likewise have protective effects that decrease the risk of respiratory complications in vulnerable patients.