Cardiovascular and metabolic manifestations of heat stroke and severe heat exhaustion.

We prospectively studied the clinical, biochemical (including creatine phosphokinase (CPK) isoenzymes) and electrocardiographic features of exertional heat stroke in 13 patients (group 1) and severe heat exhaustion in 14 patients (group 2). Despite initial presentations with severe hyperthermia, tachycardia and hypotension, only one patient with heat stroke had myocardial ischemia. The CPK isoenzymes were not indicative of myocardial damage in any patient. The patients with heat stroke were somewhat more dehydrated than those with heat exhaustion as measured by differences in serum creatinine, sodium and osmolality, and the former (group 1) had a significantly lower initial glucose level (P less than 0.05). Although significant differences in potassium were not observed in the pretreatment samples, at 12 hours the serum potassium was significantly lower in group 1 (P less than 0.05). This suggests that this group may have been more potassium-depleted at the time of heat stroke. Prompt recognition and vigorous therapy were successful in rapidly lowering high temperatures and in preventing serious complications.