Pre-Hospital Induced Hypothermia Improves Outcomes in a Pig Model of Traumatic Hemorrhagic Shock.

Abstract

Extensive preclinical evidence suggests that induced hypothermia can protect tissues from ischemia-reperfusion injury, reduce organ damage, and improve survival in the advanced stages of shock. We assessed the effects of induced hypothermia on the hemodynamic parameters and coagulation capacity during hemorrhagic shock (HS) and fluid resuscitation, in a pig model of HS with multiple intestinal perforations. Pigs (n=16) were randomized into 2 groups: a hypothermia (HT) group (n=8, 34°C) and a normothermia (NT) group (n=8, 38°C). Hypothermia to 34°C was induced with a cold blanket at the pre-hospital stage. Traumatic HS shock was induced using multiple intestinal perforations. Pulse indicator continuous cardiac output (PiCCO) was used to monitor hemodynamic changes. Coagulation capacity was measured using thromboelastography (TEG) at baseline as well as during resuscitation periods. Survival was documented for 72 h post-trauma. Mortality in the hypothermic HS group was low, but there were no significant differences in mortality between the groups (mortality=2/8 HT vs. 5/8 NT, p=0.137). During hypothermia, the heart rate, extravascular lung water index (EVLWI), oxygen uptake index (VO2), and oxygen delivery index (DO2) in the HT group were significantly lower than those in the NT group. There were no significant differences between the 2 groups in the other hemodynamic indices or prothrombin time. Analyses of thromboelastometry at 34°C during hypothermia showed significant differences for reaction time (R) and alpha angle, but not for maximal amplitude (MA). Rewarming reversed the coagulation changes induced by hypothermia. Induced mild hypothermia (34°C) in the pre-hospital stage affects hemodynamic parameters and the coagulation system but does not worsen outcomes in a pig HS model. The hypothermia-induced coagulation changes were reversed during rewarming without evidence of harmful effects. Our results suggest that pre-hospital induced hypothermia can be performed carefully following major trauma.