EFFECTS OF LOCAL HYPOTHERMIA ON LIMB VIABILITY IN A SWINE MODEL OF ACUTE LIMB ISCHEMIA DURING PROLONGED DAMAGE-CONTROL RESUSCITATION

Background: New strategies are needed to mitigate further tissue injury during traumatic limb ischemia in cases requiring damage control resuscitation (DCR). Little is known about the pathophysiology and injury course in acute limb ischemia (ALI) with DCR in polytraumatized casualties. We therefore investigated the effects of therapeutic limb hypothermia in a swine model of ALI and DCR. Methods: Fifteen swine underwent a published 6-h DCR protocol of hemorrhage and then resuscitation. After hemorrhage, animals were randomized to 5 degrees C or 15 degrees C cooling of one hindlimb; the contralateral limb serving as an uncooled control. Physiologic variables, limb temperature, and limb tissue metabolites (glucose, lactate, and pyruvate) were measured throughout the DCR protocol. Muscle and nerve biopsies were obtained after the 6-h protocol. Results: Lactate and pyruvate levels were significantly lower in the cooled limbs than in the uncooled control limbs but did not differ between the 5 degrees C and 15 degrees C groups. Tissue glucose levels did not differ between the 5 degrees C group, the 15 degrees C group, and controls. Mean histologic muscle score was significantly higher in the 5 degrees C group than in controls (P = 0.03). Mean nerve histology scores did not differ between the 5 degrees C and paired control limbs, or between the mean muscle and nerve histology scores of the 15 degrees C and paired control limbs. Conclusion: Cooling to 15 degrees C significantly reduced local tissue metabolites compared to paired controls, while producing no significant increase in histologic damage, whereas cooling to 5 degrees C increased histologic muscle damage. These results suggest an approach to prevention of ischemic injury through local hypothermia but warrant further functional testing.