47. The Impact of Intraoperative Temperature on Venous Thromboembolism and Flap Pedicle Thrombosis in Patients Undergoing Head and Neck Microsurgical Reconstruction

Abstract

PURPOSE:in vitro studies on platelet have shown that lower temperatures encourage aggregation. Anesthesia guidelines recommend the prevention of hypothermia (T < 36º). This study explores the impact of intraoperative body temperature on venous thromboembolism (VTE). METHODS: All patients who underwent head and neck reconstruction with free tissue transfer from January 2012 through March 2022 were included. Intraoperative temperature readings were extracted in one-minute intervals. A median was calculated for every five consecutive readings to create a five-minute temperature reading. A median value under 36 º was considered an onset of hypothermia. VTE events and thrombosis of the free flap pedicle (arterial or venous) were the study outcomes, and they were recorded within 30 days of the index surgery. Statistical analysis was performed using bivariate and multivariate regression analysis. RESULTS: 895 patients were included. The VTE rate was (n=37, 4.0%). The incidence of patients developing at least one onset of hypothermia was (n=720, 80%). The mean for Caprini score in those who experienced hypothermia didn’t differ significantly from those who were normothermic (≥ 36º) for the whole surgery (6.55±1.76 vs. 6.46±1.60, p=0.533). The rate of VTE in those who experienced hypothermia was significantly higher than in those who were normothermic for the whole surgery (n=35/720, 3.9% vs. n=2/175, 0.22%, p=0.026). This association persisted even after controlling for Caprini score, the number of hypothermic onsets, and length of surgery (OR, 5.478, 95%CI: 1.222-24.557). CONCLUSION: Hypothermia onset is associated with an increased rate of VTE postoperative, even after controlling for patient factors.