Introduction: In patients with isolated severe traumatic brain injury (TBI), the effect of controlled, therapeutic hypothermia on outcomes has been studied extensively. What is not well understood, however, and the purpose of this study, was to examine the impact of noninduced, nontherapeutic hypothermia on outcomes in these patients.
Methods: A retrospective review of the institutional trauma registry at the Los Angeles County + University of Southern California Medical Center was performed to identify all trauma patients admitted to the surgical intensive care unit (SICU) with isolated severe TBI from January 2000 to December 2008. Patients were classified as hypothermic (core temperature [Tc] ≤35°C) or normothermic (Tc >35°C) based on their first Tc recorded on SICU admission. The primary outcome measure was in-hospital mortality, and secondary outcomes included SICU and hospital length of stay.
Results: During the study period, 1,403 patients sustaining an isolated severe TBI were admitted to the SICU. After excluding 122 patients with missing temperature data, 1,281 patients were analyzed. Hypothermia (Tc ≤35°C) on SICU admission was identified in 10.9% (n = 140) of the study population, with the remaining 89.1% (n = 1,141) being normothermic (Tc >35°C). After adjusting for differences in baseline characteristics between the two groups, patients who were hypothermic on SICU admission were found to be significantly less likely to survive (odds ratio, 2.9; 95% confidence interval, 1.3, 6.7; p < 0.013). A penetrating mechanism of injury, Injury Severity Score ≥25, and undergoing an exploratory laparotomy before admission were found to be independent risk factors for the development of hypothermia on SICU admission.
Conclusion: For patients who have sustained isolated severe TBI, the presence of noninduced, nontherapeutic hypothermia on SICU admission is associated with a significant increase in mortality. The impact of preventative measures used to avoid the development of hypothermia and the effectiveness of measures for restoring normothermia warrant further investigation.