Rudzki, Stephan, Sinclair, Wade H., Leicht, Anthony S., Patterson, Mark J., Fogarty, Alison L., and Winter, Susan (2008) Comparison of the safety and efficacy of three cooling methods in hyperthermic subjects. In: Medicine and Science in Sports and Exercise (40) S5-S6. From: ACSM 2008 Annual Meeting of the American College of Sports Medicine, 28-31 May 2008, Indianapolis, IN, USA.

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Abstract

PURPOSE: The only effective treatment for heat injury (heatstroke) is rapid cooling. Ice water baths are the gold standard for cooling, but are not practical in remote or austere settings, such as those encountered by military personnel on operations. Safe and effective methods of cooling body core temperature are essential to prevent severe complications from heatstroke.To compare the safety and effectiveness of three different methods of cooling (ice packs: ICE, fan and water spray: FAN and chilled IV saline: IV) on the same subject.

METHODS: Twelve healthy, active males volunteered to participate in three trials. Trials differed in the cooling technique (ICE, FAN and IV) and were presented in a balanced order while subjects laid in a supine position. Participants undertook a continuous walk-run (2 min at 6 km/hr and 4 min at 10 km/hr, respectively) in an environment of 34°C, 62% RH until body core temperature reached 40.0°C. Body core temperature was monitored by an ingestible temperature pill. A 3-lead ECG was employed to monitor cardiac activity during the cooling period. The ICE treatment consisted of 5 bags of ice cubes (22 cm x 20 cm; 1 kg) placed left and right groin, left and right armpit and back of neck for 40 min. The FAN treatment consisted of 500 mL of 32°C water being sprayed over the body every 5 min for 40 min. An industrial fan induced air speeds of 8.4 m/s at the head and 3.8 m/s at the feet. The IV treatment consisted of infusion of 2 L of 4°C over a 24-min period with body core temperature being monitored for a further 16 min.

RESULTS: All three cooling methods were effective in reducing body core temperature (ICE: 0.07°C/min, FAN: 0.09°C/min and IV: 0.08°C/min). FAN was significantly quicker than ICE (P<0.05) in reducing body core temperature, although no other between-trial differences were observed. There were no cardiac arthymias observed during the cooling treatments in any trials. The rate of cooling for ice packs was higher than previously reported. This is likely due to the large ice volumes as opposed to cold packs and the melting of the ice such that cold water was in contact with a large surface area.

CONCLUSIONS: All three methods are capable of providing acceptable rates of cooling for hyperthermic patients, although IV is a more logistically available method for cooling troops operating in hot and remote environments.

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