Skip to content

BASICS

  • Core temperature <35°C (95°F) due to environmental cold exposure
  • May develop over hours to days
  • All body systems affected
  • Synonym: Accidental hypothermia

EPIDEMIOLOGY

  • Predominantly affects young children and elderly
  • More common in males
  • Higher risk in elderly due to decreased metabolic rate and impaired temperature detection
  • CDC reported 16,911 hypothermia deaths (1999-2011)
  • Often secondary to other medical or environmental factors

ETIOLOGY AND PATHOPHYSIOLOGY

  • Overwhelming environmental cold stress
  • Decreased heat production: hypopituitarism, hypothyroidism, adrenal insufficiency
  • Increased heat loss: immersion, burns
  • Alcohol intoxication contributes to 68% of cases
  • Impaired thermoregulation: CNS tumors, stroke
  • Pediatric: high surface area to mass ratio, limited glycogen stores, poor heat production

RISK FACTORS

  • Alcohol/drug intoxication
  • Bronchopneumonia
  • Cardiovascular disease, cardiac arrest
  • Cold-water immersion, prolonged exposure
  • Burns, dermatologic disorders
  • Endocrine disorders (myxedema, hypoglycemia)
  • Malnutrition, hepatic/renal failure, sepsis
  • CNS dysfunction, mental illness, trauma

GENERAL PREVENTION

  • Appropriate clothing, especially head, hands, feet
  • Carry survival gear outdoors (foil blankets, dry clothes)
  • Avoid alcohol in cold environments
  • Early recognition and preventive actions (warm fluids, shelter)
  • Identify meds that predispose to hypothermia (neuroleptics, sedatives)

COMMONLY ASSOCIATED CONDITIONS

  • Addison disease, hypothyroidism, hypopituitarism
  • Diabetes, ketoacidosis
  • CNS dysfunction, congestive heart failure
  • Pulmonary infection, sepsis
  • Uremia

DIAGNOSIS

History

  • History of environmental exposure often evident
  • May be unclear in indoor hypothermia
  • Symptoms: confusion, dizziness, dyspnea, altered mental status

Physical Exam

  • Core temperature measurement: esophageal probe most accurate
  • Mild (32-35°C): lethargy, shivering, tachypnea, tachycardia, hyperventilation, loss of fine motor skills
  • Moderate (28-32°C): delirium, hypotension, hypoventilation, cyanosis, arrhythmias (bradycardia, prolonged PR/QT)
  • Severe (<28°C): rigidity, areflexia, apnea, ventricular fibrillation/asystole, dilated/fixed pupils
  • Pediatric: bright red cold skin, lethargy, rapid temperature drop, altered mental status key clue

DIFFERENTIAL DIAGNOSIS

  • Stroke
  • Intoxication/overdose
  • Diabetes complications
  • Hypothyroidism, hypopituitarism

DIAGNOSTIC TESTS & INTERPRETATION

  • Labs: ABG (temperature corrected), CBC, electrolytes, BUN/creatinine, glucose, calcium, magnesium
  • Coagulation panel, fibrinogen, blood cultures, LFTs, amylase, cardiac enzymes
  • Alcohol and toxicology screen
  • Imaging: C-spine, chest, abdomen X-rays; head CT if altered mental status
  • ECG: hyperkalemia (>12 mmol/L) linked to nonsurvival

TREATMENT

General Measures

  • Basic life support, airway security
  • Remove wet clothing, dry and insulate patient
  • Passive rewarming for mild hypothermia (shivering present)
  • Active rewarming for moderate/severe hypothermia or nonshivering patients
  • Warm IV fluids, warm humidified oxygen
  • Do not delay transport; start rewarming early

Medications

  • Treat underlying infection/sepsis with antibiotics
  • D50W for hypoglycemia (1 mg/kg)
  • Thiamine 100 mg if alcoholic or cachectic
  • Naloxone 2 mg if opioid suspected
  • Levothyroxine 150–500 µg for myxedema
  • Sodium bicarbonate for severe acidosis
  • Avoid repeated use of epinephrine, lidocaine, procainamide until temp >30°C

Rewarming Strategies

  • Mild: passive external warming and heated IV fluids
  • Moderate: active external warming + heated IV fluids
  • Severe: active internal/core rewarming (ECMO, CPB preferred)
  • Body cavity lavage (thoracic, peritoneal) as secondary option
  • Hemodialysis or hemofiltration as adjunct

Cardiac Arrhythmias

  • Atrial fibrillation, sinus bradycardia common and often revert with rewarming
  • Defibrillation only once for ventricular fibrillation, defer further shocks until rewarmed
  • External pacing preferred if needed

ADMISSION, INPATIENT, AND NURSING CONSIDERATIONS

  • Admit all patients with core temp <32°C or underlying illness
  • Monitor core temperature, cardiac rhythm, blood pressure
  • Correct metabolic acidosis and electrolyte imbalances
  • Avoid overheating dextrose solutions (>60°C caramelizes glucose)
  • Use normal saline (warmed) for volume replacement, avoid lactated Ringer’s
  • Watch for electrolyte shifts during rewarming (potassium)
  • Prevent fluid overload and monitor for hypotension

ONGOING CARE

  • Monitor cardiac rhythm, urine output, electrolytes, blood gases, glucose frequently
  • Continue treatment of underlying cause post-acute episode

DIET

  • Warm fluids if alert and able to swallow
  • Counsel to avoid alcohol in cold environments
  • Refer for social support (housing, clothing, heat) as needed

PATIENT EDUCATION

  • Patients with cardiovascular disease should exercise caution outdoors in cold
  • Awareness of hypothermia risks and preventive measures

PROGNOSIS

  • Mortality depends on age, underlying illnesses, severity
  • <5% mortality in healthy patients; >50% if comorbidities present
  • Mortality increases significantly with age (>65 years)

COMPLICATIONS

  • Cardiac arrhythmias, hypotension, sepsis
  • Electrolyte disturbances (hyperkalemia, hypoglycemia, acidosis)
  • Rhabdomyolysis, pneumonia, pulmonary edema, ARDS
  • GI complications (pancreatitis, peritonitis, ileus)
  • Acute tubular necrosis, bladder atony
  • Thromboses/DIC, gangrene, compartment syndrome
  • Neurologic: seizures, cerebral ischemia, delirium

REFERENCES

  1. Dow J, Giesbrecht GG, Danzl DF, et al. Wilderness Medical Society Clinical Practice Guidelines for the out-of-hospital evaluation and treatment of accidental hypothermia: 2019 update. Wilderness Environ Med. 2019;30(4S):S47-S69.
  2. Paal P, Gordon L, Strapazzon G, et al. Accidental hypothermia—an update: the content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM). Scand J Trauma Resusc Emerg Med. 2016;24(1):111.
  3. Haverkamp FJC, Giesbrecht GG, Tan ECTH. The prehospital management of hypothermia—an up-to-date overview. Injury. 2018;49(2):149-164.

Clinical Pearls

  • Most common cause of hypothermia in the US: cold exposure with alcohol intoxication
  • Begin resuscitation unless obvious lethal injuries, rewarm to 33–35°C and reassess
  • Hypothermia, coagulopathy, and acidosis ("trauma triad") increase mortality risk
  • Use esophageal or rectal thermometer for accurate core temperature measurement
  • Avoid repeated defibrillation and drug administration until core temp >30°C
  • Monitor electrolytes closely during rewarming, especially potassium