Mortality impact of hypothermia after cavitary explorations in trauma

Background: Admission hypothermia (core temperature ≤ 35°C) is an independent risk factor for mortality after trauma. The predictive value of perioperative core temperatures during acute trauma surgery, however, although widely employed as a criterion for initiating damage control, is unknown. We hypothesized that for trauma patients undergoing laparotomy or thoracotomy, early postoperative hypothermia is a predictor of mortality. Methods: After institutional review board (IRB) approval, all critically ill trauma patients undergoing cavitary surgery (laparotomy or thoracotomy) at a level 1 trauma center from 01/1998 to 07/2006 were identified from the trauma registry. Immediate postoperative core temperature (Tc) was used to classify patients as hypothermic (Tc ≤ 35°C) or normothermic (Tc > 35°C). The profoundly hypothermic subgroup of patients with a Tc < 33°C was also analyzed. Results: During the study period, 2,489 patients required cavitary surgery, 1,252 of whom (50%) were admitted to the intensive care unit (ICU). On arrival in the ICU 15% of the patients had a Tc ≤ 35°C and were more likely to be ≥ 55 years old (12% versus 7%; p = 0.04); in addition, they were hypotensive on admission (25% versus 13%; p < 0.001), had a lower admission Glasgow Coma Score (GCS; 11 ± 5 versus 14 ± 3; p < 0.001), a higher Injury Severity Score (ISS; 29 ± 15 versus 22 ± 12; p < 0.001), higher head and chest Abbreviated Injury Scale (AIS), and greater intraoperative blood loss (2.6 ± 2.4 l versus 1.7 ± 1.8 l; p < 0.001). When compared to patients who were normothermic at the end of their operation, hypothermic patients had a significantly higher mortality (35% versus 8%; p < 0.001). With decreasing Tc, there was a stepwise increase in mortality. Compared to patients with a Tc > 35°C, the relative risk of death for patients with a Tc between 35°C and 33°C was 4.0, and that for patients with a Tc ≤ 33°C it was 7.1. After adjusting for multiple differences between groups, postoperative hypothermia remained an independent predictor of mortality (adjusted odds ratio [OR] 3.2; 95% confidence interval [CI] 1.9-5.3; p < 0.001). Conclusions: Postoperative hypothermia is common in critically injured patients requiring cavitary surgery and is an independent predictor of mortality. The impact of measures to maintain or restore normothermia in the operating room warrants further investigation.