Hypothermia, Accidental

• • 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

Epidemiology

• • 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

Symptoms and Signs

• • 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

Laboratory Findings

• • 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

• • 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

• • Physical exam

  • Temperature

  • ECG

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

• • 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

Treatment Monitoring

• • Continuous temperature monitoring

  • Careful observation for unsuspected disease masked by hypothermia

Complications

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

  • Coagulopathies (including disseminated intravascular coagulation) are seen occasionally

  • Pancreatitis and acute renal ...