exertional heat injury

A mild form of heat stroke that occurs in athletes & other individuals who engage in vigorous exercise in a warm environment. Etiology: (risk factors) 1) environmental temperature > 80 degrees F 2) relatively high humidity 3) insufficient acclimatization 4) poor conditioning 5) obesity 6) inadequate hydration 7) advanced age 8) previous heatstroke Clinical manifestations: 1) manifestations common to all forms of heat injury a) headache b) weakness c) nausea & vomiting d) vertigo e) faintness f) tachycardia g) hypotension h) pallor 2) other manifestations a) muscle cramps b) chills c) piloerection on trunk & upper extremities d) tachypnea e) ataxia f) incoherent speech g) loss of consciousness h) core temperature 102-104 F i) copious sweating Laboratory: 1) complete blood count (CBC) a) hemoconcentration b) thrombocytopenia (uncommon) c) evidence of hemolysis on peripheral smear (uncommon) 2) serum chemistries a) hypernatremia b) elevated serum transaminases c) elevated muscle enzymes (LDH, CPK, aldolase) d) hypocalcemia e) hypophosphatemia f) hypoglycemia (occasionally) g) elevated unconjugated bilirubin (if hemolysis) 3) disseminated intravascular coagulation panel (rarely abnormal) a) D-dimer b) fibrinogen 4) urinalysis a) myoglobinuria (uncommon) b) urine Na⁺ > 40 meq/L with acute tubular necrosis (ATN) c) urine osmolality < 350 mOsm/kg 5) prothrombin time Special laboratory: -> electrocardiogram Differential diagnosis: 1) heat stroke 2) heat exhaustion 3) sepsis 4) myocardial infarction 5) neuroleptic malignant syndrome Management: 1) lower core temperature to 100 degrees F a) apply cold packs or fluids b) cooling fan 2) massage extremities 3) infuse hypotonic fluids with glucose 4) follow-up within 1 week a) ensure complete recovery b) work-up & management of pre-existing illness as indicated 5) patient education a) exercise in morning hours when temperature & humidity are lowest b) adequate hydration before & during exercise c) avoid alcohol before & during activity

Related

hyperthermia (pyrexia) neuroleptic malignant syndrome

References

Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1178-80