((SLB-046)) (SLB-046) Impacts of Extreme Temperature Events on Intraoperative Hypotension: A Multicenter Cohort Study of 276,515 Patients

Background: Extreme temperature events (ETEs), such as heat waves and cold spells, have been increasingly linked to adverse health outcomes. However, their impact on intraoperative hypotension (IOH) remains underexplored. IOH, defined as a mean arterial pressure (MAP) < 65 mmHg, is associated with increased postoperative complications and mortality. Understanding the relationship between ETEs and IOH risk is essential for optimizing perioperative management in the context of climate change.

Objectives: This study investigates the association between ETEs and IOH in a large multicenter cohort of patients undergoing major surgery. We assess how different levels of temperature extremes influence the risk and duration of IOH.

Methods: A retrospective cohort study was conducted using data from 276,515 patients who underwent major surgery across three academic medical centers in China (2015–2023). ETEs were defined using percentile-based temperature thresholds. Heat waves were classified as days with average temperatures at or above P95 or P97.5 for at least 3 or 4 consecutive days. Cold spells were defined as days with average temperatures at or below P5 or P2.5 for at least 3 or 4 consecutive days. The primary outcome was IOH incidence, and secondary outcomes included IOH duration and severe IOH (lasting ≥ 10 minutes). Adjusted logistic regression and generalized linear models were used to examine associations, controlling for demographic, surgical, and environmental confounders.

Results: Of the total cohort, 48,023 patients were exposed to heat waves, 42,615 to cold spells, and 185,877 were unexposed. Heat waves (P95_3d) were associated with a reduced IOH risk (adjusted OR: 0.87, 95% CI: 0.85–0.89, P < 0.001) and shorter IOH duration (β [SE]: -0.66 [0.32], P = 0.041). In contrast, cold spells (P5_3d) increased IOH risk (adjusted OR: 1.03, 95% CI: 1.01–1.05, P = 0.016) and prolonged IOH duration (β [SE]: 0.97 [0.33], P = 0.003). Subgroup analyses indicated that younger women undergoing non-cardiac surgery were particularly susceptible to IOH during cold spells (adjusted OR: 1.04, 95% CI: 1.00–1.08, P = 0.039).

Conclusions: This study demonstrates a significant association between ETEs and IOH, with heat waves reducing IOH risk and cold spells increasing it. These findings highlight the need for tailored perioperative management strategies to mitigate ETE-related risks, particularly for vulnerable patient subgroups.