Association of Immediate Postoperative Temperature in the Surgical Intensive Care Unit with 1-Year Mortality: Retrospective Analysis Using Digital Axillary Thermometers

Background: Postoperative body temperature is closely associated with prognosis although there is limited research regarding this association at postoperative intensive care unit (ICU) admission. Furthermore, no studies have used digital axillary thermometers to measure postoperative body temperature. This study investigated the association between mortality and postoperative temperature measured using a digital axillary thermometer within 10 minutes after ICU admission. Methods: This retrospective observational study evaluated data from adult patients admitted to an ICU after elective or emergency surgery. The primary outcome was 1-year mortality after ICU admission. Multivariable logistic regression analysis with restricted cubic splines was used to evaluate the association between temperature and outcomes. Results: We evaluated data from 5,868 patients admitted between January 1, 2013 and May 31, 2016, including 5,311 patients (90.5%) who underwent noncardiovascular surgery and 557 patients (9.5%) who underwent cardiovascular surgery. Deviation from the median temperature (36.6°C) was associated with increases in 1-year mortality (≤36.6°C: linear coefficient, –0.531; P<0.001 and ≥36.6°C: spline coefficient, 0.756; P<0.001). Similar statistically significant results were observed in the noncardiovascular surgery group, but not in the cardiovascular surgery group. Conclusions: An increase or decrease in body temperature (vs. 36.6°C) measured using digital axillary thermometers within 10 minutes of postoperative ICU admission was associated with increased 1-year mortality. However, no significant association was observed after cardiovascular surgery. These results suggest that postoperative temperature is associated with longterm mortality in patients admitted to the surgical ICU in the postoperative period.