Am Fam Phys 2005;71:2133; Med Let 2003;47:58; Nejm 2002;346:1978

Cause:Heat accumulation > dissipation mechanisms; classic form typically w exertion or infection in elderly, drug use (phenothiazines, anticholinergics, diuretics, -blockers, alcohol) in heat waves; exertional type common in athletes, soldiers and tradespeople exercising in the heat

Pathophys:Blunting of heat-dissipating mechanisms: decreased thermal gradient in hot/humid environment; decreased physiologic compensatory mechanisms in elderly, mentally disabled, those on many types of medications (eg, antihypertensives, cocaine, neuroleptics, etc), poorly heat-acclimated individuals; dehydration has not been linked with exertional heatstroke; cascade of events triggered by hyperthermia, results in failure of hypothalamic temperature modulation and cascade of pathophysiologic events

Of classic: 20 deaths/100,000 in heat waves

Sx:CNS impairment; ranges from coma to mild confusioin/ataxia

Si:Core temperature >40°+C; esophageal probe, rectal probe accurate; all other means of measuring temperature are not accurate (JAT 2007;42:333); anhidrosis

20% in-hospital mortality

Death in up to 20% if untreated; CNS impairment; hepatorenal failure, DIC, rhabdomyolysis

Lab:CBC, CMP, lactate, DIC labs, CK; r/o other causes of hyperthermia (eg, infection, malignant hyperthermia, seizure, brain mass)

Rx:Medications (antipyretics, muscle relaxants) ineffective

Immediate cooling essential; methods include immersion in ice water, evaporation with wet skin and warm air, packing groin, axillae and abdomen with ice; mortality/morbidity thought to be associated with time spent above certain (unknown) critical temperature; hydrating is not sufficient as primary tx.