What is the recommended management for mild, moderate, and severe hypothermia?

Management of Hypothermia

Immediate Actions for All Hypothermic Patients

All hypothermic patients must be immediately protected from further heat loss by moving to a warm environment, removing wet clothing, insulating from the ground, covering the head and neck, and shielding from wind—these steps are critical regardless of severity. 1

• Core temperature measurement is mandatory using esophageal, bladder, or oral probes capable of reading below 35°C; never rely on clinical appearance alone for severity classification 2, 3
• Avoid axillary measurements as they consistently underestimate core temperature by 1.5-1.9°C, leading to dangerous treatment errors 2, 3
• Handle all patients with moderate-to-severe hypothermia gently to prevent triggering fatal arrhythmias 2

Severity-Based Treatment Algorithm

Mild Hypothermia (32-35°C)

Passive rewarming with blankets combined with active external warming methods is the standard approach for mild hypothermia. 1, 2

• Apply forced-air warming blankets, heating pads, or radiant heaters in addition to insulating blankets 2, 3
• Offer high-calorie foods or warm drinks if the patient is alert and can swallow safely 2
• Monitor for deterioration as patients may progress to more severe hypothermia 1

Moderate Hypothermia (28-32°C)

Moderate hypothermia is a medical emergency requiring immediate activation of the emergency response system and aggressive active external rewarming. 1, 2

• Use forced-air warming blankets as the primary rewarming method, which can achieve rates of approximately 2.4°C/hour compared to 1.4°C/hour with passive blankets alone 2
• Administer warmed intravenous isotonic crystalloid fluids 2
• Provide humidified, warmed oxygen 2
• Handle the patient extremely gently during all interventions to avoid precipitating ventricular fibrillation 2
• Place an insulating barrier between any heat source and skin, following manufacturer instructions to prevent burns 2
• Monitor continuously for cardiac arrhythmias, particularly bradycardia (which may be physiologically beneficial) 2

Severe and Profound Hypothermia (<28°C)

For severe hypothermia, cardiopulmonary bypass provides the most rapid core temperature increase and improves survival odds, particularly in cardiac arrest. 1, 2

• Activate emergency response system immediately 1, 2
• Continue all measures for moderate hypothermia while arranging for invasive core rewarming 2
• Consider body-cavity lavage with warmed fluids or extracorporeal rewarming (ECMO, hemodialysis, or cardiopulmonary bypass) when available 1, 2, 4
• Alternative core rewarming includes warm-water lavage of the thoracic cavity and extracorporeal blood warming with partial bypass 1
• Intermittent hemodialysis can achieve stable rewarming at approximately 2.0°C/hour in hemodynamically unstable patients without cardiac arrest when ECMO/CPB is unavailable 4
• Do not delay urgent procedures such as airway management and vascular access due to concerns about cardiac irritability 1

Cardiac Arrest Management in Hypothermia

Begin CPR immediately in any hypothermic patient without signs of life, regardless of core temperature, and continue throughout rewarming as survivors with good neurologic outcomes have been reported. 2

• Deliver defibrillation shocks immediately for ventricular fibrillation or ventricular tachycardia, even at very low core temperatures; animal data show successful defibrillation down to 30°C 2
• Administer epinephrine or vasopressin during cardiac arrest even in severe hypothermia; animal studies report 62% return of spontaneous circulation versus 17% with placebo 2
• Continue standard ACLS algorithms while simultaneously rewarming; hypothermia does not alter the core resuscitation protocol 1, 2
• After return of spontaneous circulation, maintain controlled rewarming to a target core temperature of 32-34°C before transitioning to routine post-arrest care 2
• Avoid anti-arrhythmic drugs as they have not demonstrated benefit and carry risk of drug accumulation 2

Rewarming Targets and Endpoints

Target a minimum core temperature of 36°C before considering the patient stable, and cease rewarming at 37°C as higher temperatures are associated with poor outcomes. 2, 3, 5

• Monitor core temperature every 5-15 minutes depending on severity 2
• Each 1°C drop in temperature causes a 10% reduction in coagulation factor function, making temperatures below 34°C a critical threshold for coagulopathy 3, 5
• In post-cardiac arrest patients, avoid rapid active warming while maintaining temperature between 32-36°C 5

Critical Pitfalls to Avoid

• Never use cold IV fluid boluses for treating accidental hypothermia; this is only indicated for therapeutic hypothermia 2, 3
• Never assume coagulopathy is absent based on standard laboratory tests run at 37°C, as body temperatures below 34°C compromise blood coagulation 3
• Never rely on passive rewarming alone at 33°C or below; active measures are required at this temperature 2
• Body-to-body rewarming does not provide advantage over other active rewarming modalities such as chemical heat packs or forced-air systems and is not recommended 2
• For the "hypothermia wrap technique" (chemical heat blankets, plastic/foil layers, insulating blankets), only use in individuals with decreased responsiveness wearing damp—not saturated—polyester fleece who cannot be moved 2

Monitoring for Complications During Rewarming

• Continuously monitor for rewarming shock, cardiac arrhythmias (particularly ventricular fibrillation), rebound hyperthermia, electrolyte abnormalities (especially post-dialysis hypophosphatemia and rebound hyperkalemia), hyperglycemia, and coagulopathy 2, 4
• Frequently inspect skin under warming devices for burns or pressure injuries 2
• Monitor for pneumonia, pulmonary edema, myoglobinuria, disseminated intravascular thrombosis, and seizures in the post-resuscitation period 6