Guided Resuscitation of Casualties across Care Continuum

The care of critically injured combat casualties, from injury through aeromedical evacuation (AE) for definitive care is complex. The operational environment provides unique challenges including limited resuscitation and availability of monitoring technologies, and environmental conditions that affect the patient and the ability to monitor them. While resuscitative care is now closer to the battle, this system relies heavily on the rapid evacuation as exemplified in the current operation where a warrior injured in Iraq is rapidly evacuated to major field hospital in theater, and after initial care the "stabilizing" casualty is evacuated to Germany. A casualty being evacuated may not be adequately resuscitated because of limited resuscitation in the field and the relatively short stay in a field hospital. Undetected inadequate resuscitation increases the risk for multiple organ failure. If a provider suspects inadequate resuscitation they are challenged to determine the best method to optimize the patient's conditions and to distinguish between physiological changes and the effect of the environment and resultant hypothermia on these indices. While fluids are the mainstay of resuscitation, their administration is not risk free, and inappropriate resuscitation (inadequate or excessive) increases morbidity and mortality. Current monitoring is not sensitive to hypoperfusion or intravascular status. There are no studies of the use of novel indices to detect occult hypoperfusion or predict fluid responsiveness during the early care and evacuation of critically injured casualties; nor are there any studies of the effect of hypothermia on these measures. This proposal is military unique in that it uses the current combat resuscitation protocol and provides care in a time frame and under environmental conditions consistent with rapid casualty evacuation. Using a well established animal model this three group randomized repeated measures study addresses the following aims: (1) Control for environmental conditions and thermal protection to mimic field and AE of combat casualties to determine if there is a difference in skeletal muscle O₂ saturation due to a decrease in body temperature. (2) Describe the perfusion status of critically injured hemorrhagic shock victims during combat resuscitation and AE using standard and novel oxygenation and hemodynamic indices. (3) Determine if there are changes in functional hemodynamic indices during hemorrhagic shock and resuscitation indicative of occult hypoperfusion and fluid responsiveness.