Written by Sam Parnell
Cold water immersion resulted in significantly faster cooling rates for patients with exertional hyperthermia compared to passive cooling measures.
Why does this matter?
Exertional heat stroke is defined as hyperthermia with core temperature greater than 40°C/104°F associated with central nervous system dysfunction after strenuous activity. Exertional heat stroke is among the leading causes of death in young athletes, and the incidence of exertional heat related illness is expected to continue to rise due to global climate change. Management is focused on immediate removal from any heat sources and rapid cooling measures. However, what cooling measures are best supported by the current evidence?
Is cold water immersion the best way to chill?
This was a systematic review and meta-analysis of 63 studies of adults with exertional hyperthermia. Water immersion techniques appeared to be the most efficacious methods to rapidly lower core body temperature [cold water (14-17 °C/57.2-62.6 °F), colder water (8-12 °C/48.2-53.6°F) and ice water (1-5 °C/ 33.8-41 °F)] and were significantly faster than passive cooling. Figure 2 from the article below nicely summarizes the cooling rates for the different cooling techniques that were studied.
There were several limitations in this study, and the amount of evidence for exertional heat illness is still quite limited. However, based on low to very low certainty of evidence, water immersion techniques (1-17 °C water) rapidly lowered core body temperatures and should be considered first line treatment for exertional hyperthermia when possible.
I got an email from John Kiel U.S. Army. Turns out arm immersion is equally effective.
First aid cooling techniques for heat stroke and exertional hyperthermia: A systematic review and meta-analysis. Resuscitation. 2020 Mar 1;148:173-190. doi: 10.1016/j.resuscitation.2020.01.007. Epub 2020 Jan 22.
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