Induced hypothermia after high-energy soft-tissue injury and subsequent hemorrhagic shock

Many cases of hypothermia (HT) occur in trauma victims subjected to soft tissue injury and hemorrhage. The aim of the present study was to study the effects of HT on the combination of these insults. A standardized gunshot wound was inflicted on the right hind leg of 14 anesthetized piglets. They were then exsanguinated of 50% of their blood volume and randomized to normothermia or HT (30 degrees C). The animals were observed for 4 h after the injury with measurements of hemodynamics, oxygen consumption, and of plasma catecholamines and electrolytes. The insults reduced cardiac output and the arterial pressure by approximately 50%, but no further reduction occurred when HT was induced. The oxygen extraction ratio increased from approximately 35% to 75% in both groups. The gradual reduction of oxygen consumption in HT animals (P < 0.05) decreased the oxygen extraction ratio to around 50%. Heart rate, the serum potassium and creatinine concentrations, and the leukocyte counts were all maintained closer to baseline in the presence of HT. Hypothermia tended to decrease oxygen extraction and was associated with less evidence of tissue injury. These effects are potentially beneficial in soft-tissue trauma combined with hypovolemia.