Hypothermia and Bleeding Risk in Cardiac Surgery: A Warming Opportunity for Prevention

Introduction: Hypothermia during and after cardiac surgery is common but modifiable. Even mild temperature reduction can impair coagulation and platelet function, increasing the risk of bleeding. When hypothermia persists into the postoperative period, the likelihood of transfusion and complications such as reexploration rises. Despite these known physiologic effects, temperature management practices remain inconsistent, and strategies such as prewarming, active intraoperative warming, and the use of warmed fluids are underutilized. This quality improvement project aimed to evaluate the impact of intraoperative and postoperative hypothermia on bleeding outcomes to guide patient blood management interventions.


Methods: We retrospectively reviewed 24,005 adult patients who underwent cardiac surgery with cardiopulmonary bypass between 2018 and 2024 at a single center. Intraoperative hypothermia was defined as temperature < 35°C following bypass separation. Postoperative hypothermia was defined by ICU admission temperature. The primary outcome was major bleeding, defined as surgical reexploration, transfusion of >10 RBC units, or procoagulant use. Secondary outcomes included total blood product use, ICU stay, and hospital stay. Multivariable logistic and negative binomial models were used to adjust for surgical and clinical factors.


Results: Intraoperative hypothermia occurred in 17% of cases and was independently associated with major bleeding (OR 1.35; 95% CI 1.11–1.64; p< 0.01). Postoperative hypothermia occurred in 14% of patients and was associated with greater transfusion burden (GMR 1.35; 95% CI 1.24–1.47; p< 0.01) and increased risk of major bleeding (OR 1.31; p=0.01). These associations persisted after risk adjustment.


Conclusions: Both intraoperative and postoperative hypothermia were associated with increased bleeding and transfusion requirements, independent of patient or procedural complexity. These findings support routine use of active warming and suggest that temperature management should be a formal component of perioperative blood conservation strategies. Hypothermia is a preventable risk factor with significant clinical impact.