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  • • Occurs when body core temperature exceeds 40 °C and produces severe CNS dysfunction

    • Result of imbalance between heat production and dissipation

    • Humans dissipate heat via skin by radiation, conduction, convection, and evaporation

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Epidemiology

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  • • Kills approximately 4000 persons each year in the United States

    • Most often affects young people who are exercising in hot environment (military, athletes, laborers, etc.)

    • Sedentary heat stroke is disease of the elderly and can be predicted when ambient temperature > 32.2 °C and relative humidity reaches 50-76%

    • Predisposing factors include:

    • -Dermatitis

      -Use of phenothiazines, β-blockers, diuretics, and anticholinergics

      -Unrelated fever

      -Obesity

      -Alcoholism

      -Heavy clothing

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Symptoms and Signs

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  • • Sudden coma in hot environment

    • Patient temperature > 40 °C is diagnostic

    • Prodrome of dizziness, headache, nausea, chills, and gooseflesh of arms and chest rarely seen

    • Confusion, belligerence, or stupor may precede coma

    • Skin is pink or ashen and sometimes, paradoxically, dry and hot

    • Profuse sweating also common

    • Heart rate ranges from 140 to 170 bpm

    • Hyperventilation may reach 60 breaths a minute with respiratory alkalosis

    • Pulmonary edema and bloody sputum may develop in severe cases

    • Jaundice is common in first few days after onset

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Laboratory Findings

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  • • No characteristic laboratory abnormalities

    • Hypocalcemia is common

    • Hypophosphatemia may occur

    • Aspartate aminotransferase (AST), lactic dehydrogenase (LDH), and creatine kinase (CK) may be elevated in first few days

    • Acidosis can result from renal failure or lactic acidosis

    • Proteinuria and granular and RBC casts are seen in initial urine specimens

    • Disseminated intravascular coagulation (DIC) pattern not uncommon

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  • • Temperature must be taken rectally

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  • • Physical exam including rectal temperature

    • Serum electrolytes

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  • • Patient should be cooled rapidly

    • -Spraying patient with water that is 15 °C and fanning with warm air is most efficient

      -Immersion in ice water bath also effective

    • Monitor the rectal temperature often

    • Stop cooling when patient's temperature reaches 38.9 °C

    • Shivering controlled with phenothiazines

    • Oxygen should be administered, intubate as needed for Pao2 < 65 mm Hg

    • Fluid, electrolyte management guided by frequent laboratory measurements

    • IV mannitol early if myoglobinuria present

    • DIC may require heparin

    • Acute renal failure may require hemodialysis

    • Inotropes for cardiac insufficiency

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Surgery

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Prognosis

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  • • Bad prognostic indicators:

    • -Temperature > 42.2 °C

      -Coma > 2 hours

      -Shock

      -Hyperkalemia

      -AST > 1000 U/L in first 24 hours

    • 10% mortality in those treated promptly

    • Deaths in first few days due to cerebral damage, late deaths from bleeding or organ failure (kidney, liver, heart)

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Prevention

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  • • Adherence to graduated schedule of increasing performance that allow acclimatization over 2-3 weeks

    • Unrestricted access to drinking water

    • Clothing and equipment should be lightened

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References

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