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- A core temperature of <35°C (95°F)
- May take several hours to days to develop
- Patients with cold-water immersion may appear dead but can sometimes still be resuscitated.
- System(s) affected: all body systems
- Synonym(s): accidental hypothermia
- Predominant age: very young and the elderly
- Predominant sex: male > female
More common in elderly due to lower metabolic rate, impaired ability to maintain normal body temperature, and impaired ability to detect temperature changes
Estimates vary widely; typically a secondary issue
Etiology and Pathophysiology
- Overwhelming environmental cold stress
- Decreased heat production
- Increased heat loss
- Impaired thermoregulation
- Alcohol consumption
- Cardiovascular disease
- Cold-water immersion
- Dermal dysfunction (burns, erythrodermas)
- Drug intoxication
- Endocrinopathies (myxedema, severe hypoglycemia)
- Excessive fluid loss
- Hepatic failure
- Hypothalamic and central nervous system (CNS) dysfunction
- Mental illness; Alzheimer disease
- Prolonged cardiac arrest
- Prolonged environmental exposure
- Renal failure
- Trauma (especially head)
- Appropriate clothing, with particular attention to head, feet, and hands
- For outdoor activities, carry survival bags with rescue foil blanket for use if stranded or injured.
- Avoid alcohol.
- Alertness to early symptoms and initiating preventive steps (e.g., drinking warm fluids)
- Identify medications that may predispose to hypothermia (e.g., neuroleptics, sedatives, hypnotics, tranquilizers).
Commonly Associated Conditions
- Addison disease
- CNS dysfunction
- Congestive heart failure
- Pulmonary infection
Presentation varies with the temperature of the patient at the time of presentation.
History of prolonged exposure to cold may make the diagnosis obvious, but hypothermia may be overlooked in other situations, especially in comatose patients. Always obtain a core temperature if hypothermia is suspected.
- Esophageal temperature is most accurate, minimally invasive method of assessing core temperature (1)[C].
- Must have secure airway
- Probe inserted into lower 3rd of esophagus
- Peripheral thermometers (tympanic membrane, temporal artery, axillary, or oral) associated with reduced accuracy
- Exam findings vary with the temperature of the patient at the time of presentation.
- Mild (32–35°C)
- Lethargy and mild confusion
- Loss of fine motor coordination
- Increased BP
- Peripheral vasoconstriction
- Hyperactive reflexes
- Moderate (28–32°C)
- Arrhythmias (prolonged PR interval, AV junctional rhythm, accelerated idioventricular rhythm, prolonged QT interval, altered T waves)
- Semicoma and coma
- Muscular rigidity
- Generalized edema
- Slowed reflexes
- Severe (<28°C)
- Very cold skin
- No pulse: ventricular fibrillation or asystole
- Pupils (dilated <27°C; fixed and dilated <27°C)
- Mild (32–35°C)
Use specially designed thermometers that can record low temperatures and measure core temperatures.
- Infants may present with bright red, cold skin and very low energy.
- A child’s body temperature drops faster than an adult does when immersed in cold water.
- Cerebrovascular accidents
- Drug overdose
- Complications of diabetes, hypothyroidism, hypopituitarism
Diagnostic Tests & InterpretationInitial Tests (lab, imaging)
- Arterial blood gases (corrected for temperature)
- CBC and platelet counts
- Serum electrolytes; BUN/creatinine; glucose; calcium; magnesium
- Coagulation studies; fibrinogen level
- Blood culture
- Liver function studies; amylase
- Cardiac enzymes
- Alcohol level and toxicology screen
- Cervical spine, chest, and abdomen x-rays, if appropriate
- Bedside ultrasound to assess hemodynamics
- CT of the head for any concern regarding mental status
Follow-Up Tests & Special Considerations
Serum cortisol and TSH if underlying endocrine dysfunction (hypothalamus stimulates release of hormones in response to hypothermia)
Serum potassium >12 mmol/L associated with nonsurvival