Following protocol registration, the authors conducted a retrospective cohort study of intermediate- to high-risk elective noncardiac surgery patients (2016) using National Surgical Quality Improvement Program data. The authors conducted Bayesian mediation analysis of the relationship between preoperative frailty (exposure, using the Risk Analysis Index), serious complications (mediator), and 30-day mortality (outcome), comprehensively adjusting for confounders. The authors estimated the total effect of frailty on mortality (composed of the indirect effect mediated by complications and the remaining direct effect of frailty) and estimated the proportion of the frailty–mortality association mediated by complications.
The authors identified 205,051 patients; 1,474 (0.7%) died. Complications occurred in 20,211 (9.9%). A 2 SD increase in frailty score resulted in a total association with mortality equal to an odds ratio of 3.79 (95% credible interval, 2.48 to 5.64), resulting from a direct association (odds ratio, 1.76; 95% credible interval, 1.34 to 2.30) and an indirect association mediated by complications (odds ratio, 2.15; 95% credible interval, 1.58 to 2.96). Complications mediated 57.3% (95% credible interval, 40.8 to 73.8) of the frailty–mortality association. Cardiopulmonary complications were the strongest mediators among complication subtypes.
Complications mediate more than half of the association between frailty and postoperative mortality in elective noncardiac surgery.
- Moderate-to-severe complications are common after major surgery and can have substantial impacts on long-term outcomes
- Preoperative frailty is strongly associated with postoperative complications and mortality
- In a retrospective cohort study of intermediate- to high-risk elective noncardiac surgery patients, complications mediated over half of the association between frailty and postoperative mortality
- Cardiopulmonary complications contributed to this association with a higher probability than renal or infectious events