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  • • Uncontrolled lowering of core body temperature below 35 °C by exposure to cold

    • EtOH facilitates induction of hypothermia by producing sedation (inhibiting shivering) and cutaneous dilation

    • Heart is most sensitive organ to cooling and is subject to ventricular fibrillation or asystole when temperature drops to 21-24 °C

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Epidemiology

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  • • Elderly patients living alone in inadequately heated homes

    • Alcoholics exposed to the cold during a binge

    • People engaged in winter sports

    • People lost in cold weather

    • Predisposing diseases include:

    • -Myxedema

      -Hypopituitarism

      -Adrenal insufficiency

      -Cerebral vascular insufficiency

      -Mental impairment

      -Cardiovascular disorders

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Symptoms and Signs

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  • • Mentally depressed (somnolent, stuporous, or comatose)

    • Cold

    • Pale or cyanotic

    • Shivering absent below 32 °C

    • Slow and shallow respirations

    • Usually normotensive and bradycardic

    • At temperatures < 32 °C, patients may appear to be dead

    • Frostbitten or frozen extremities

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Laboratory Findings

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  • • Severe hypoglycemia is common

    • Elevated serum amylase in 50%

    • Elevations of aspartate aminotransferase (AST), lactic dehydrogenase (LDH), and creatine kinase (CK) enzymes

    • ECG shows PR lengthening, pathognomonic J wave at junction of the QRS and ST segment

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  • • When severely hypothermic, patients should not be declared dead until measures for rewarming and resuscitation have failed

    • Mild hypothermia (32-35 °C) can be treated by passive rewarming with continuous monitoring of rectal or esophageal temperatures

    • Active rewarming is indicated for temperatures below 32 °C, cardiovascular instability, or failure of passive rewarming

    • Methods for rewarming include:

    • -Immersion in warm water

      -Inhalation of heated air

      -Pleural and peritoneal lavage

      -Extracorporeal blood warming

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  • • Physical exam

    • Temperature

    • ECG

    • Central venous pressure and pulmonary capillary wedge pressure should be kept below 12-14 cm H20 to minimize edema

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  • • Immersion in warm water (40-42 °C) will raise body temperature 1-2 °C per hour

    • Pleural irrigation via 2 right thoracostomy tubes (anterior, posterior) with warm saline (40-42 °C)

    • Peritoneal lavage involves giving warm (40-45 °C) crystalloid solutions at 6 L/h which will raise temperature 2-4 °C per hour

    • Partial cardiopulmonary bypass (CPB) is the most efficient technique and is indicated for ventricular fibrillation, severe hypothermia, or frozen extremities

    • Partial CPB with flows of 6-7 L/min can raise core temperature 1-2 °C every 3-5 minutes

    • Endotracheal intubation and mechanical ventilation are often necessary

    • Bretylium tosylate 10 mg/kg is best drug for ventricular fibrillation

    • Antibiotics are often indicated for pneumonitis

    • Hypoglycemia should be treated with IV D50

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Treatment Monitoring

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  • • Continuous temperature monitoring

    • Careful observation for unsuspected disease masked by hypothermia

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Complications

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  • • Increased capillary permeability may lead to generalized and pulmonary edema upon rewarming

    • Coagulopathies (including disseminated intravascular coagulation) are seen occasionally

    • Pancreatitis and acute renal failure (ARF) common in < 32 °C

    • Failure to respond to treatment should suggest adrenal insufficiency

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