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For further information, see CMDT Part 37-03: Accidental Systemic Hypothermia

Key Features

Essentials of Diagnosis

  • Systemic hypothermia is a core body temperature (CBT) below 35°C

  • Accurate CBT measurement must be obtained using a low-reading core temperature probe than measures as low as 25°C

  • The CBT must be over 32°C before terminating resuscitation efforts

  • Extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass may be considered in hypothermic patients with hemodynamic instability or cardiac arrest

General Considerations

  • Risk factors

    • Diabetes mellitus and other endocrine dysfunctions (hypothyroidism, adrenal insufficiency, hypopituitarism)

    • Kidney or liver dysfunction

    • Psychiatric conditions

    • Poor nutrition

    • Sedentary lifestyle

    • Homelessness, inadequately heated housing, inadequate or wet clothing

    • Occupational or recreational exposure

    • Prior cold weather injury

    • Pharmacologic effects

    • Sepsis, infection

    • Hypoglycemia

  • Heat loss occurs more rapidly with

    • High wind velocity ("windchill factor")

    • Water immersion or wet clothing

    • Direct contact with a cold surface

  • Accidental hypothermia may occur in the hospital setting due to

    • Prolonged postoperative hypothermia or administration of large amounts of refrigerated stored blood products (without rewarming)

    • Rapid infusion of intravenous fluids

    • Prolonged exposure of an undressed patient during resuscitation or surgical procedures

  • Systemic hypothermia

    • Depresses physiologic function, resulting in decreased respiratory drive, oxygen consumption, central or peripheral nerve conduction, gastrointestinal motility, myocardial repolarization, metabolism of drugs

    • May decrease activity of coagulation cascade and the immune response

Clinical Findings

Symptoms and Signs

Systemic hypothermia

  • In mild cases with core temperature between 35°C and 32°C (stage I):

    • Shivering

    • Impaired coordination

    • Poor judgment

    • Hemodynamic stability

    • Normal level of consciousness

  • With core temperature between 32°C and 28°C (stage II):

    • Shivering stops

    • Bradycardia, dilated pupils, slowed reflexes, cold diuresis, and confusion and lethargy ensue

  • With core temperature between 28°C and 24°C (stage III)

    • Loss of consciousness

    • Vital signs present

  • Below 24°C (stage IV):

    • Vital signs lost

    • Coma, loss of reflexes, asystole or ventricular fibrillation, which may lead the clinician to assume that patient is dead despite reversible hypothermia

Hypothermia of the extremities

  • Exposure of the extremities to cold produces immediate localized vasoconstriction followed by generalized vasoconstriction

  • When the skin temperature falls to 25°C, the area becomes cyanotic

  • At 15°C, there is a deceptively pink, well-oxygenated appearance to the skin. Tissue damage occurs at this temperature

Differential Diagnosis

  • Infection

  • Other cause of altered mental status (eg, hypoglycemia, drugs, stroke)

  • Hypothyroidism

  • Anorexia or malnutrition (poor fat stores)

  • Adrenal insufficiency

  • Burns

  • Spinal cord injury

Diagnosis

Laboratory Tests

  • Must assess acid-base status; electrolytes (particularly potassium); glucose; kidney, liver, and pancreas function; and coagulation; and must exclude rhabdomyolysis

Diagnostic Procedures

  • ECG may reveal J wave or Osborn wave (positive deflection in the terminal portion of the QRS complex, most notable in leads II, V...

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