Hypothermia

Hypothermia is defined as a core body temperature of 95°F (35°C) and can be further defined as mild (90–95°F, or 32–35°C), moderate (82–90°F, or 28–32°C), or severe (below 82°F, or 28°C). Accidental hypothermia is the most common cause of severe hypothermia. Return of spontaneous circulation has been documented from temperatures as low as 57.6°F (14.2°C) in infants and 56.7°F (13.7°C) in adults. For ventricular fibrillation due to hypothermia, bretylium is currently the ACLS agent of choice.

Differential Diagnosis

• Exposure
  –Alcohol intake is a common risk factor because it both alters thermoregulation and promotes risk-taking behavior
  –Shivering, amnesia, ataxia, and dysarthria occur with mild hypothermia (>89.6°F, or >32°C)
  –Stupor, absence of shivering, atrial fibrillation, and/or bradycardia occur with moderate hypothermia (82–90°F, or 28–32°C)
  –Coma, ventricular fibrillation, apnea, asystole, and/or areflexia occur with severe hypothermia (<82.4°F, or <28°C)
• Sepsis
  –Mild hypothermia is common in sepsis, especially in infection with gram-negative rods (e.g., E. coli), and in the elderly
• Hypothyroidism
  –Up to 10 times more common in females
  –May be of autoimmune, postsurgical, or pituitary etiology
  –Symptoms include hypothermia, hair loss, dry skin, pretibial myxedema, weight gain, constipation, and prolonged relaxation phase of deep tendon reflexes

• Stroke
  –Hypothermia may occur because of altered cerebral thermoregulation

• Hypovolemic shock
  –Poor peripheral perfusion often results in mild hypothermia

• Massive blood transfusion
  –Due to refrigerated blood that is rapidly transfused without warming

Workup and Diagnosis

• A complete history and physical examination are essential, especially if there is no definite history of exposure
  –Careful examination of the extremities and dependent body parts for signs of frostbite
  –Assess core temperature (rectal temperature is preferred) using a low-temperature thermometer
• ECG may reveal Osborne J waves if temperature is less than 91.4°F (33°C)
• Laboratory studies may include CBC, electrolytes, BUN/creatinine, glucose, calcium, liver function tests, coagulation studies, blood and urine cultures, TSH, free T₄, arterial blood gas analysis, creatine kinase, and urinalysis (evaluate for rhabdomyolysis)
• Chest X-ray may be indicated to assess for infection in cases of suspected sepsis
• Head CT scan to evaluate for altered mental status
• Blood cultures are indicated if infection and/or sepsis are suspected

Treatment

• “No person is dead until they are warm and dead”—this underscores the ability to resuscitate patients from profound hypothermia
• Exposure is treated by passive rewarming to prevent further heat loss (e.g., remove wet clothes, cover with blankets), active external rewarming (e.g., radiant warmers, heating blankets), and/or active core rewarming (e.g., warmed IV fluids, pleural lavage, cardiopulmonary bypass, dialysis)
• Hypothyroidism: Treat mild cases with levothyroxine, myxedema coma with IV thyroxine and IV hydrocortisone
• Sepsis: Administer appropriate antibiotics, vasopressors for hypotension, and fluids for resuscitation
• Shock: Volume expansion with crystalloid solutions (normal saline or lactated Ringer's) or blood products; vasopressors (e.g., norepinephrine, phenylephrine); positive inotropes (e.g., dopamine, dobutamine)

Book Source Details

• Book Title: In a Page: Signs and Symptoms
• Author(s): Scott Kahan, Ellen G. Smith
• Year of Publication: 2004
• Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.

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Copyright Details: In a Page: Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

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• Back to symptom: Temperature symptoms: Introduction (review 1519 causes)
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More About This Book: Title: In a Page: Signs and Symptoms Authors: Scott Kahan, Ellen G. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2004 ISBN: 1-4051-0368-X

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