Efficacy of field treatments to reduce body core temperature in hyperthermic subjects

Purpose: To contrast the effects of three postcooling techniques in reducing body core temperature (Tc) in exercise-induced hyperthermic participants on the cessation of exercise. Methods: Eleven healthy active male volunteers were cooled during a 40-min period using three different methods: ice packs to the neck, axillae, and groin (ICE); water spray and fan (FAN); and 2 L of chilled (20°C) intravenous saline administered during a 20-min period (IV). Rate of decrease in Tc, cardiovascular responses, and any incidence of reported adverse effects were investigated. Trials were presented in a counterbalanced order with the volunteers' body core temperature being elevated to 40.0°C on three occasions via an intermittent walk-run (2 min at 6 km·h-1 and 4 min at 10 km·h-1) protocol conducted within a climate-controlled chamber (34.2 ± 0.5°C and 62.3 ± 3.1% relative humidity). Results: Rate of Tc reduction during the first 20 min of ooling was greater for FAN compared with ICE (0.09 ± 0.02°C·min-1 vs 0.07 ± 0.02°C·min-1, P 0.05). Three participants complained of numbness or paresthesia in their arm or hand during administration of the chilled saline, although these symptoms resolved within 5 min of ceasing the infusion. Conclusions: All three cooling techniques reduced Tc and would be suitable for first aid application in a field setting during transportation to adequate medical facilities. Chilled IV saline did not produce any contraindications, providing a suitable alternative for Tc cooling