Rectal Temperature Cooling Using 2 Cold-Water Immersion Preparation Strategies

CONTEXT: Cold-water immersion (CWI) is essential to treat patients with exertional heatstroke (EHS). Experts recommend that patients with EHS be immersed in water between 1.7°C and 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 in the recommended range. OBJECTIVES: To (1) compare the cooling rates of individuals immersed in a water bath kept at 10°C (CON) or 17°C water with 75.7 L (20 gal) of ice added to it immediately upon immersion (ICE) and (2) examine perceptual responses before, during, and after cooling. DESIGN: Crossover study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twelve individuals (7 men, 5 women; age = 22 ± 2 years, height = 176.0 ± 12.8 cm, mass = 74.5 ± 10.6 kg). INTERVENTIONS: Participants exercised in the heat until rectal temperature was 39.5°C. They then immersed themselves in CON (initial water volume = 681 ± 7.6 L, 10.0°C ± 0.03°C) or ICE (initial water volume = 605.7 ± 7.6 L water at 17.0°C ± 0.03°C with 75.7 L ice) until rectal temperature was 38°C. Thermal sensation and environmental symptoms questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling. MAIN OUTCOME MEASURE(S): Rectal temperature cooling rates, thermal sensation, ESQ responses. RESULTS: Participants exercised for similar durations (CON = 39.6 ± 18.2 minutes, ICE = 38.8 ± 14.3 minutes, Z11 = 0.94, P = .38) and had similar thermal sensation and ESQ scores immediately postexercise each day (P values > .05). They cooled quickly and at similar rates in both conditions (CON = 0.20°C ± 0.06°C/min, ICE = 0.21°C ± 0.12°C/min, t12 = 0.72, P = .49). Perception data were similar between conditions during and after cooling (P < .05). CONCLUSIONS: Clinicians can cool patients with EHS quickly by adding ice to water that has warmed to above expert recommendations. Adding ice to a water bath at the time of EHS emergencies could save time, energy, and resources instead of always maintaining water bath temperatures within expert-recommended ranges.