This study was undertaken to compare cooling in room air (27 degrees C, 20% RH), ice slush surface cooling, and peritoneal lavage cooling (6-10 degrees C) as methods for lowering body temperature in an anesthetized dog heatstroke model. We anesthetized 19 animals with sodium pentobarbital (25 mg/kg) intravenously, and maintained them in an ambient temperature of 42-46 degrees C with a water heating blanket approximately 2.0 h until rectal temperatures rose to 43.2 +/- 0.2 degrees C. At the maximum rectal temperature, the heating blankets were removed, and animals were cooled, observed until death occurred or 18 h elapsed, and then sacrificed. The data demonstrate that maximum cooling rates of rectal temperature were: peritoneal lavage, 0.56 degrees C/min; ice slush, 0.11 degrees C/min; and 27 degrees C air cooling, 0.06 degrees C/min. The incidence of 18-h survival for lavage-cooled dogs when supported with normothermic dialysis every 4 h was significantly greater than for either ice slush or air cooled dogs.