Hypothermia in critically ill patients can be difficult to treat with standard rewarming (SR) techniques. We developed a rewarming method that is significantly faster than SR. Percutaneously placed femoral arterial and venous catheters were connected to the inflow and outflow side of a countercurrent fluid warmer to create a fistula through the heating mechanism (CAVR). Over a 10-month period 34 hypothermic (temperature less than 35 degrees C) patients were treated. Eighteen received SR only; CAVR was added to SR in the remaining 16 patients. Both groups were similar in APACHE II, Injury Severity, and Acute Physiology scores, prewarming blood and fluid requirements, and incidence of coagulopathy. Hypothermia resolved in 39 minutes with CAVR vs. 3.23 hours with SR (p less than 0.001). This was associated with an improved survival after moderately severe injury (p = 0.04), and a significant reduction in blood and fluid requirements, organ failures, and length of ICU stay.