Postoperative Hypothermia after Cardiac Surgery: A Retrospective Cohort Study of Incidence and Risk Factors

Abstract

Background: Postoperative hypothermia (PH) may result in perioperative complications such as adverse cardiovascular events, coagulopathy with consecutive blood loss, and wound infection. Patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) are at risk for hypothermia throughout the postoperative period. Objective: To determine the incidence and risk factors of PH in patients after open cardiac surgery. Materials and Methods: The present study was a retrospective cohort study of patients that underwent open cardiac or thoracic aortic surgery using CPB between January and December 2013. Patient characteristics, clinical data, and perioperative outcomes were abstracted and analyzed. PH was defined as body temperatures of less than 36℃ upon arrival at the cardiac surgical intensive care unit (CSICU). Postoperative outcomes including bleeding from the chest tube, postoperative inotropic support, ventilator days, CSICU length of stay, and mortality were reviewed. Results: Seven hundred sixty patients were included in the present study with 60.4% male, a mean age of 61.7 years, and 92.4% elective surgery with 96.3% first time surgery. The incidence of PH was 43.4%. Multiple logistic regression analysis demonstrated that factors associated with PH were increasing age (odds ratio 1.013 per year, 95% CI 1.002 to 1.023, p=0.020), female patients (odds ratio 1.40, 95% CI 1.03 to 1.89, p=0.032), deep hypothermia during CPB (odds ratio 2.33, 95% CI 1.26 to 4.30, p=0.007), and administration of more than 3L of intravenous fluid including crystalloids, colloids, and blood products, after separation of CPB until discharge from the operating room (OR) (odds ratio 1.52, 95% CI 1.09 to 2.12, p=0.014). Conclusion: Approximately 43.4% of the cardiac surgical patients develop hypothermia following open cardiac or thoracic aortic surgeries. Factors associated with PH were increasing age, female patients, deep hypothermia during CPB, and administration of more than 3L of intravenous fluid after separation of CPB until discharge from the OR. Keywords: Hypothermia; Postoperative; Cardiac surgical procedures; Cardiopulmonary bypass