Context:

Cold-water immersion (CWI) is essential to treat exertional heatstroke (EHS). Experts recommend EHS patients be immersed in water between 1.7°C to 15°C within 30 minutes of collapse. Some clinicians fill cooling tubs several hours before exercise, keep the tub in hot conditions, and then add ice in the event of an EHS emergency. No data exist on whether adding ice to water at the time of treatment is as effective as keeping water within expert-recommended ranges.

Objective:

We compared the cooling rates of individuals immersed in a water bath kept at 10°C (CON) or 17°C water with 75.7L (20 gal) of ice added to it immediately upon immersion (ICE). We also examined perceptual responses before, during, and after cooling.

Design:

Randomized, counterbalanced, crossover study

Setting:

Laboratory

Patients or Other Participants:

Twelve individuals (7 men, 5 women; age:22±2y; mass:74.5±10.6kg; height:176.0±12.8cm).

Interventions:

Participants exercised in the heat until TREC was 39.5°C. They immersed themselves in CON (initial water volume=681±7.6L, 10.0±0.03°C) or ICE (initial water volume=605.7±7.6L water at 17.0±0.03°C with 75.7L ice) until TREC was 38°C. Thermal sensation and environmental symptom questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling.

Main Outcome Measures:

TREC cooling rates, thermal sensation, ESQ responses

Results:

Subjects exercised for similar durations (CON=39.6±18.2min, ICE=38.8±14.3min, Z11=0.94, P=0.38) and had similar thermal sensation and ESQ scores immediately post-exercise each day (P>0.05). Subjects cooled quickly and at similar rates in both conditions (CON=0.20±0.06°C/min; ICE=0.21±0.12°C/min, t12=0.72, P=0.49). Perception data were similar between conditions during and after cooling (P<0.05).

Conclusions:

Clinicians can cool EHS patients quickly by adding ice to water that has warmed and is above expert recommendations. Adding ice to water baths at the time of EHS emergencies could save time, energy, and resources instead of always maintaining water bath temperatures within expert-recommended ranges.

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