Time course of recovery and heat acclimation ability of prior exertional heatstroke patients.

Our understanding of the time course of recovery from exertional heatstroke (EH) and the heat acclimation ability of prior EH patients is limited. This manuscript reviews previous findings regarding recovery from EH and presents original research involving the heat acclimation ability of 10 prior EH patients (PH) and 5 control subjects. Heat acclimation, by definition, distinguishes heat-intolerant from heat-tolerant prior heatstroke patients. Nine PH exhibited normal heat acclimation adaptations (40.1 degrees C, 7 d, 90 min.d-1), thermoregulation, sweat gland function, whole-body sodium and potassium balance, and blood values at 61 +/- 7 d after EH. One PH (subject A) did not adapt to exercise in the heat, was defined heat intolerant, but subsequently was declared heat tolerant (11.5 months post-EH). Three PH exhibited large, unexpected increases in serum CPK levels, which resolved upon subsequent testing, and were probably related to their detrained state and the exercise which they performed. It was concluded that: 1) sleep loss and generalized fatigue were the most common predisposing factors for PH; 2) recovery from EH was idiosyncratic and may require up to 1 year in severe cases; 3) PH were not hereditarily heat intolerant, prior to EH; 4) no measured variable predicted recovery from EH, or heat acclimation responses; 5) heat intolerance occurs in a small percentage of prior heatstroke patients, and may be transient or persistent.