Hypothermia in massive transfusion: have we been paying enough attention to it?

The development of acidosis, coagulopathy, and hypothermia has been shown to adversely affect survival after injury. Significant attention has focused on the correction of the early coagulopathy in those requiring massive transfusion (MT). We sought to characterize the importance of temperature as a risk factor for poor outcome relative to the changes in MT resuscitation that have occurred.

Data were obtained from a multicenter prospective cohort study of adults with blunt injury with hemorrhagic shock. MT was defined as 10 U or more of packed red blood cell (PRBC) during 24 hours. The lowest 24-hour temperature was categorized into groups (<34.0°C, 34.1-35.0°C, 35.1-36.0°C, and >36°C). A Kaplan-Meier analysis and a multivariate logistic regression were used to analyze temperature survival differences over time and independent risks of mortality after controlling for all important confounders.

In the MT cohort (n = 604), as temperature decreased, shock parameters, early coagulopathy, injury severity, and blood component transfusion requirements significantly increased. A Kaplan-Meier comparison revealed a dose-response relationship with a temperature lower than 34°C resulting in the greatest mortality. Logistic regression analysis demonstrated that a temperature lower than 34°C was associated with a greater independent risk of mortality of more than 80% after controlling for differences in shock, coagulopathy, injury severity, and transfusion requirements (odds ratio, 1.87; 95% confidence interval, 1.18-3.0; p = 0.007). When the cohort was stratified into high or low plasma to red blood cell transfusion ratio groups (high fresh frozen plasma [FFP]/PRBC, ≥1:2 vs. low FFP/PRBC, <1:2), regression modeling demonstrated that a temperature lower than 34°C was associated with a twofold higher independent risk of mortality, only in the low FFP/PRBC transfusion group.

A temperature of 34°C seems to define a clinically significant hypothermia in MT. The independent risks of mortality were greatest in those who received a low FFP/PRBC transfusion ratio. These data suggest that the prevention of hypothermia may be as important as addressing early coagulopathy. Further research is required to verify if the prevention or correction of hypothermia improves the outcome of patients requiring MT.