Effect of systemic hypothermia on local soft tissue trauma-induced microcirculatory and cellular dysfunction in mice.

OBJECTIVE: Changes in body temperature occur as a systemic reaction to severe trauma; however, its role in the manifestation of injury remains unclear. Thermoregulatory responses vary considerably from fever to hypothermia. Although hypothermic trauma patients seem to have a worse prognosis, there is the question whether hypothermia per se or the severity of trauma producing the hypothermia is responsible for aggravated injury and increased mortality rate. The present study unravels how moderate to severe systemic hypothermia modulates local microcirculatory dysfunction and cellular injury in local soft tissue trauma. DESIGN: Prospective, experimental study. SETTING: Research laboratory at a university. SUBJECTS: C57BL/6J mice. INTERVENTIONS: A model involving standardized drop weight device-induced tissue trauma and high-resolution multifluorescence microscopy in the dorsal skinfold chamber was used to show arteriolar vasoconstriction, reduction of blood flow, nutritive perfusion failure, and apoptotic cell death at 1 hr after trauma. MEASUREMENTS AND MAIN RESULTS: During the 8-hr posttrauma observation period, microcirculation, but not apoptosis, restituted to almost baseline level. Concomitant systemic hypothermia of either 34 degrees C or 30 degrees C did not affect late manifestation of apoptotic cell death but aggravated initial microcirculatory dysfunction and inhibited recovery during the 8-hr follow-up period. CONCLUSIONS: Our study provides evidence that systemic hypothermia may aggravate soft tissue trauma-associated microcirculatory dysfunction. These experimental results clearly support clinical efforts to prevent hypothermia in the acutely traumatized patient.