Hypothermia is a significant contributor to mortality in severely injured patients. Rewarming is an enormous challenge, especially in those who require operative or angiographic intervention. In this patient population, external warming methods are only capable of reducing further heat loss, whereas active rewarming adds heat to the body's core but is invasive. This article analyzes our initial experience with a minimally invasive, continuous, automated, and easily portable intravascular rewarming technique using the Alsius Corporation's CoolGard system. The records of 11 hypothermic critically injured patients presenting to our level 1 trauma center over a 6-month period were reviewed. The patients' mean age was 39 +/- 22 years, 7 (64%) were male, and 7 (64%) had blunt mechanisms of injury. The mean injury severity score was 40 +/- 16, and the mean initial systolic blood pressure was 91 +/- 60 mm Hg. The mean core temperature at the initiation of rewarming was 33.6 +/- 1.0 degrees C, and the mean rewarming rate was 1.5 +/- 1.0 degrees C/h. Six patients died (55%), two of acute exsanguination and four of unsurvivable traumatic brain injuries. One patient developed a deep vein thrombosis at the femoral catheter site and experienced a nonfatal pulmonary embolus. Our experience demonstrates that active intravascular balloon-catheter rewarming represents a practical, automated technique for the immediate and continuous treatment of hypothermia in all phases of the acute care of trauma patients.