Association between intraoperative hypotension and myocardial injury after major open abdominal surgery

Myocardial injury after non-cardiac surgery (MINS) contributes to mortality after major open abdominal surgery. While intraoperative hypotension (IOH) is a proposed cause, its impact-defined using comprehensive thresholds-in this specific high-risk cohort remains underexplored. This study aimed to determine the association between the severity and duration of IOH and MINS.

We assessed patients undergoing open abdominal surgery with invasive blood pressure monitoring in a single-center retrospective cohort study conducted between June 2016 and July 2019. The primary exposure, IOH, was defined using three absolute and three relative thresholds of mean arterial pressure (MAP), according to established literature and clinical consensus. The primary outcome was MINS (serum Troponin T (TnT) ≥ 0.03 ng/mL within 30 days after surgery). A multivariable logistic regression analysis was applied to model the exposure-outcome relationship, adjusting for potential clinical confounders.

Of the 8,281 patients screened, 1,461 met the inclusion criteria. MINS occurred in 175 patients (12.0%). MAP below three absolute thresholds (≤65, ≤60, and ≤55 mmHg) and three thresholds relative to the preinduction MAP (decreases of >30, >40, and >50% from baseline) were independently associated with MINS. For MAP ≤60 mmHg, the odds of MINS increased with longer durations of hypotension, rising from 1.54 (95% CI 0.98-2.44) for 1-5 min to 3.81 (95% CI 2.20-6.61) for ≥21 min. At the longest duration, lower MAP thresholds were associated with higher risk (OR 3.66 for ≤65 mmHg; 3.81 for ≤60 mmHg; and 8.42 for ≤55 mmHg). Similar associations were observed for relative MAP reductions.

In major open abdominal surgery patients, IOH, either based on absolute and relative thresholds, is independently and cumulatively associated with MINS. Associations based on absolute MAP thresholds appeared more consistent, whereas those based on relative reductions showed greater variability.