To the Editor.
—Dr Frank and colleagues' attempted to determine the specific value of perioperative forced-air warming on patient outcome. However, failure to randomize surgeons and failure to control for and report several important variables,2 such as preoperative total body thermal baselines, intraoperative core temperature changes, administration of vasodilator or vasoconstrictor drugs, patient body fat content, and patient weight—to—surface area ratios significantly weaken the results.Peripheral prewarming significantly changes postinduction core temperature decline, as 81% of the typical 1.6°C first-hour temperature decline is ascribed to redistribution rather than actual loss of body heat, necessitating specific considerations beyond simple initial core temperature. The core temperature of warmed patients will decline identically to that of "unwarmed" patients during the first hour despite forced-air warming. The duration and course of intraoperative forced-air warming therapy clearly are important as significant effects are demonstrated only after 90 to 120 minutes. Further, core temperature declines with application
Kempen PM. Perioperative Maintenance of Normal Temperature. JAMA. 1997;278(7):545. doi:10.1001/jama.1997.03550070037022