Am Fam Phys 2005;71:2133

Cause:As in heatstroke; milder disease state in heat exhaustion; hyponatremic variety often results from voluntary hyperhydration (often related to media/advertisement stimulating concerns about dehydration)

Pathophys:As in heatstroke, though no pathophysiologic cascade leading to complications

Of hyponatremic type: typically slow, inexperienced finishers in long (marathon) races, W>M

Sx:No CNS impairment; nausea, malaise

Si:Core temperature 38-40°+C; see above for accurate temperature measurement; anhydrosis, flushing; of hyponatremic type: swelling, malaise, confusion, ataxia, possibly convulsions

Generally self-limited; can progress to heatstroke if temperature allowed to increase

Lab:Na

Rx:Removal from heat source; passive cooling; ensure adequate hydration; of hyponatremia: do not hydrate iv or po; ? small volumes (500 cc) hypertonic saline iv vs. allow renal function to compensate and decrease body water