Hypothermia

Hypothermia is a medical emergency defined by a core body temperature falling below 35°C (95°F). It occurs when heat loss exceeds heat production, most often due to prolonged exposure to cold air or wet conditions, immersion in cold water, or impaired thermoregulation from illness, intoxication, or trauma. Vulnerable groups include the elderly, infants, homeless individuals, outdoor workers, and those with alcohol or drug use or certain medical conditions.

As temperature drops, symptoms progress in stages. Mild hypothermia (32–35°C) typically presents with shivering, rapid breathing, and tachycardia. Moderate hypothermia (28–32°C) often shows diminished shivering, slowed speech, impaired coordination, confusion, and drowsiness. Severe hypothermia (<28°C) may feature absent shivering, significant mental status changes, loss of consciousness, and dangerous cardiac rhythms. People can deteriorate rapidly, and coexisting medical problems can complicate presentation.

Diagnosis relies on core temperature measurement, ideally with rectal, esophageal, or bladder thermometry, in conjunction with physical examination and vital signs. Cardiac monitoring is important due to the risk of arrhythmias. Clinicians assess need for rewarming and identify precipitating factors such as alcohol use, hypoglycemia, dehydration, or trauma.

Treatment emphasizes safety, rapid warming, and addressing underlying causes. In the field, move the person to a sheltered, dry area, remove wet clothing, insulate with dry blankets, and provide warm, nonalcoholic fluids if conscious. Avoid rough handling and limb massage. Mild cases may use passive warming; more significant hypothermia requires rapid transport and active external rewarming (heated blankets, air or water systems) and active core warming (warm IV fluids, warmed humidified oxygen) in a clinical setting. Monitor core temperature and electrolytes, treat complications, and prevent rewarming shock.

Prevention includes appropriate clothing and shelter in cold weather, hydration, avoiding alcohol, and addressing risk factors in vulnerable populations.