Heat Stroke

• • 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

Epidemiology

• • 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

Symptoms and Signs

• • 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

Laboratory Findings

• • 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

• • Temperature must be taken rectally

• • Physical exam including rectal temperature

  • Serum electrolytes

• • 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

Surgery

Prognosis

• • 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)

Prevention

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

  • Unrestricted access to drinking water

  • Clothing and equipment should ...