Background Myocardial injury after noncardiac surgery (MINS) is a common postoperative cardiovascular complication. While the metabolic score for insulin resistance (METS-IR) serves as a novel marker for insulin resistance, its relationship with MINS and its relevance to cardiovascular-kidney-metabolic (CKM) syndrome staging are not yet established.

Objective To investigate the association between preoperative METS-IR and MINS across different CKM syndrome stages.

Methods Patients who underwent noncardiac surgery at the First Medical Center of PLA General Hospital from January 2020 to December 2022 were retrospectively included. The primary outcome was MINS and the secondary outcome was acute kidney injury (AKI). Restricted cubic spline (RCS) analysis was used to assess the dose-response relationships between METS-IR and the outcomes, and multivariable logistic regression was used to analyze the associations of METS-IR with the outcomes. Stratified analyses by CKM stage were performed, with separate logistic regression models fitted in the Stage 0-1, Stage 2, and Stage 3-4 subgroups. The E-value was used to assess the influence of residual unmeasured confounders.

Results A total of 12 086 patients were included, with a mean age of 61.5 ± 9.5 years and 5 269 (43.6%) were male. The incidence of MINS was 7.1% (853/12 086) and that of AKI was 8.4% (1 010/12 086). RCS analysis showed a linear positive association between METS-IR and MINS (P for nonlinearity=0.205; overall P < 0.001). Logistic regression showed that for each 1-SD increase in METS-IR, the risk of MINS increased (OR=1.19, 95% CI: 1.07 - 1.32, P=0.002), as did the risk of AKI (OR=1.14, 95% CI: 1.02-1.28, P=0.021). Stratified analysis by CKM stage showed that the positive association between METS-IR and MINS was independent in each stage: Stage 0-1 (OR=1.30, 95% CI: 1.11 - 1.51, P=0.001), Stage 2 (OR=1.21, 95% CI: 1.06 - 1.38, P=0.004), and Stage 3-4 (OR=1.16, 95% CI: 1.03 - 1.31, P=0.013). The E-value was 1.67 (1.34 for the CI bound), indicating that moderate-strength unmeasured confounder would be required to fully explain the observed association.

Conclusion In patients undergoing noncardiac surgery, preoperative METS-IR is independently associated with the risks of MINS and AKI. Among different CKM syndrome stages, METS-IR may serve as a reference indicator for perioperative cardiorenal risk assessment.