Relation of intraoperative temperature to postoperative mortality in open colon surgery—an analysis of two randomized controlled trials

INTRODUCTION: The open surgical wound is exposed to cold and dry ambient air resulting in heat loss mainly through radiation and convection. This cools the wound and promotes local vasoconstriction and hypoxia. Carbon dioxide (CO(2)) and water vapor are greenhouse gases with a warming effect. The aim was to evaluate if warm humidified CO(2) insufflated in surgical wound can affect long-term overall mortality METHODS: This is a retrospective study of two clinical trials, where patients were randomized to warm humidified CO(2) (n = 80) or not (n = 78). All patients underwent elective major open colon surgery. Patients in the treatment group received insufflation of warm humidified CO(2) into the open wound cavity via a gas diffuser to create a local atmosphere of 100 % CO(2). Temperature in the wound cavity was measured with a heat-sensitive infrared camera. Core temperature was measured at the tympanic membrane. Median follow-up was 70.9 months. RESULTS: A multivariate analysis adjusted for age (p = 0.001) and cancer (p = 0.165) showed that the larger the temperature difference between final core temperature and wound edge temperature, the lower the overall survival rate (p = 0.050). Patients receiving insufflation of warm humidified CO(2) had a tendency to a better overall survival compared with control patients (p = 0.508). End-of-operation wound edge temperature was negatively associated with mortality (OR = 0.80, 95 % CI = 0.68-0.95, p = 0.011), whereas mortality was positively associated with age (10-year increase, OR = 1.78, 95 % CI = 1.37-2.33, p < 0.001) and cancer (OR = 8.1, 95 % CI = 1.95–33.7, p = 0.004). CONCLUSIONS: A small end-of-operation temperature difference between final core and wound edge temperature was positively associated with patient survival in open colon surgery.