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-hour DCR protocol of hemorrhage and then resuscitation. After hemorrhage, animals were randomized to 5oC or 15oC 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-hour 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 5oC and 15oC groups. Tissue glucose levels did not differ between the 5oC group, the 15oC group, and controls. Mean histologic muscle score was significantly higher in the 5oC group than in controls (p = 0.03). Mean nerve histology scores did not differ between the 5oC and paired control limbs, or between the mean muscle and nerve histology scores of the 15oC and paired control limbs.

Conclusion: Cooling to 15oC significantly reduced local tissue metabolites compared to paired controls, while producing no significant increase in histologic damage, whereas cooling to 5oC increased histologic muscle damage. These results suggest an approach to prevention of ischemic injury through local hypothermia but warrant further functional testing.