Effects of short heat exposure on human red and white blood cells.

Background: The infusion of warm intravenous fluid (IVF) is a simple and effective method used to maintain or restore core body temperature. At present, 40 degrees C is believed to be the highest temperature that can be safely administered. There is concern that temperatures greater than 40 degrees C may harm blood cells. The mixing time of IVF infused into a high-flow vein such as the superior vena cava is very short, however, approximately 300 milliseconds. We will determine the maximum temperature and exposure time tolerated by human red and white blood cells without producing injury.

Methods: Whole blood and isolated neutrophils were exposed to temperatures (40-80 degrees C) for short time intervals (150-1,200 milliseconds). Lethal injury to red and white blood cells was measured by the plasma free hemoglobin and percent viability, respectively. Neutrophil viability was measured by trypan blue staining. Sublethal injury to red and white cells was measured by osmotic fragility and oxidative burst, respectively. Neutrophil oxidative burst was measured by chemiluminescence. Control values were compared with postexposure values using analysis of variance with p < 0.05 indicating significance.

Results: Lethal injury to red blood cells did not occur until exposure at 70 degrees C for 300 milliseconds (plasma free hemoglobin, 116.3 +/- 34.7 mg%; p < 0.05). Lethal injury to neutrophils did not occur, even at exposure at 80 degrees C for 1,200 milliseconds. Sublethal injury to red blood cells did not occur until exposure at 60 degrees C for 1,200 milliseconds. Sublethal injury to neutrophils did not occur until exposure at 60 degrees C for 600 milliseconds (percent change in oxidative burst = 28.9 +/- 0.96%; p < 0.05).

Conclusions: The exposure of human red blood cells and neutrophils to temperatures up to 60 degrees C for up to 600 milliseconds does not cause lethal or sublethal injury. These findings contribute to the body of evidence supporting the use of centrally infused IVF at temperatures greater than 40 degrees C for active core rewarming.