Evaluation of methods for rapid cooling of heat induced injury, is intravenous normal saline an option?
Heat illness and its treatment remains a significant problem for the ADF, both in operational and exercise environments. A combined study by James Cook University Defence Science and Technology Organisation and the Army (Army Safety and 3 Brigade) was conducted recently in Townsville to address this.
Whilst immersion in an ice/water bath is considered the gold standard, this is prohibitively difficult in the environments above. Cold IV saline is used post cardiac arrest for brain protection but has not been validated for cooling those with heat induced injury.
We studied three methods of cooling fit soldiers, exercised in a controlled environment to a core temperature of 40 degrees centigrade. Each soldier was cooled on three separate occasions by (1) infusion of 2 L of Normal Saline over 20 minutes, (2) application of icepacks to groin, armpits and back of neck or (3) skin wetting with a high speed fan. Core temperature was monitored using an ingested radio pill, and vital signs were monitored throughout.
All methods were efficacious and safe. Skin wetting with a high speed fan appeared to be the fastest but was limited by a plateau effect. Ice and IV saline were similar in temperature reduction, but ice was the least preferred technique. This study will aid development of doctrine to treat heat illness in the operational environment.
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