What is the appropriate treatment for a patient with hypothermia?

Treatment of Hypothermia

Immediately protect the patient from further heat loss by moving to a warm environment, removing all wet clothing, and initiating active rewarming with forced-air warming blankets for moderate hypothermia (28-32°C) or active core rewarming methods for severe hypothermia (<28°C), targeting a minimum core temperature of 36°C but stopping at 37°C to avoid poor outcomes. 1, 2

Initial Stabilization and Assessment

Remove wet clothing immediately and move the patient to a warm environment, shielding from wind and insulating from cold ground surfaces. 1 Cover the head and neck, as these are major sites of heat loss. 1

Temperature Measurement

• Use oral or esophageal probes for accurate core temperature monitoring, as these provide the most reliable measurements in the emergency setting. 2, 3
• Tympanic infrared probes serve as acceptable alternatives when oral measurement is not feasible. 2, 3
• Avoid axillary measurements entirely, as they consistently read 1.5-1.9°C below actual core temperature and will lead to underestimation of severity. 2, 3
• Monitor core temperature every 5-15 minutes depending on severity. 2, 3

Critical pitfall: A patient may appear clinically stable despite severe hypothermia based on core temperature. Always base treatment decisions on measured core temperature rather than clinical presentation alone, as patients can be alert and communicative even with temperatures as low as 25°C. 4

Severity-Based Treatment Algorithm

Cold Stress (35-37°C)

• Remove from cold environment and protect from further heat loss. 1
• Passive rewarming with blankets is often adequate in healthy individuals at this temperature range. 1
• Provide high-calorie foods or warm drinks if the patient is alert and able to swallow safely. 1

Mild Hypothermia (32-35°C)

• Allow passive rewarming with at least two dry insulating blankets while increasing environmental temperature. 1, 2
• Provide high-calorie foods or drinks if alert, as shivering increases metabolic rate 5-6 times and requires substantial calorie expenditure. 1
• Active external rewarming may be used in tandem with passive methods to accelerate recovery. 1
• Monitor for signs of deterioration and protect from falls due to altered level of responsiveness. 1
• Expected rewarming rate: approximately 1.2°C/hour passively, up to 3.6°C/hour if shivering. 1, 2

Moderate Hypothermia (28-32°C)

This is a medical emergency requiring immediate activation of the emergency response system. 1

• Implement active external rewarming as the primary method, using forced-air warming blankets which can achieve rewarming rates of approximately 2.4°C/hour compared to 1.4°C/hour with passive blankets alone. 2, 3
• Alternative active external methods include heating pads, radiant heaters, or water-circulating warming blankets. 3
• When using any rewarming device, place insulation between the heat source and skin and frequently monitor for burns and pressure injury. 1
• Administer warmed intravenous fluids (43°C) centrally. 1, 5
• Provide humidified, warmed oxygen via advanced airway if needed. 1
• Handle the patient gently to avoid triggering cardiac arrhythmias. 1

Special consideration: If the patient is wearing damp (not saturated) clothing such as polyester fleece and cannot be immediately moved to a warm environment, active rewarming through the damp clothing using the hypothermia wrap technique with chemical heat blankets, plastic or foil layers, and insulative blankets is reasonable. 1

Do not use body-to-body rewarming, as it is not beneficial compared to chemical heat packs or forced-air systems. 1

Severe Hypothermia (<28°C)

This represents a life-threatening emergency with high risk for cardiac arrest. 1

• Continue all measures for moderate hypothermia while preparing for active core rewarming. 1, 2
• Consider active core rewarming methods including:
  • Peritoneal lavage with warmed fluids 1, 5
  • Body cavity lavage 6, 7
  • Extracorporeal rewarming (ECMO or cardiopulmonary bypass) for hemodynamically unstable patients 6, 7, 8
  • Intermittent hemodialysis (IHD) as an alternative when ECMO/CPB are unavailable or not indicated, achieving rewarming rates of approximately 2.0°C/hour 8
• Handle the patient extremely gently to avoid triggering ventricular fibrillation. 1, 6

Profound Hypothermia (<24°C)

• Shivering will have ceased at this temperature. 1
• Expect slow heart rate and breathing with high risk for irregular heart rhythm and cardiac arrest. 1
• Aggressive active core rewarming is the primary therapeutic modality. 1

Cardiac Arrest Management

If the hypothermic patient has no signs of life, begin CPR without delay. 1 Pulse and respiratory rates may be extremely slow or difficult to detect. 1

• If ventricular tachycardia or ventricular fibrillation is present, attempt defibrillation. 1
• If VT/VF persists after a single shock, it is reasonable to perform further defibrillation attempts according to standard BLS algorithm concurrent with rewarming strategies. 1
• Consider vasopressor medications (epinephrine or vasopressin), as animal studies demonstrate increased rates of return of spontaneous circulation (62% versus 17% with placebo). 1, 2
• Antiarrhythmic medications have not shown benefit in hypothermic cardiac arrest. 1

Rewarming Targets and Endpoints

Target a minimum core temperature of 36°C before considering the patient stable or transferring between units. 2, 3, 6

Cease rewarming after reaching 37°C, as higher temperatures are associated with poor outcomes and increased mortality. 2, 3, 6 This is a critical endpoint that must not be exceeded.

For post-cardiac arrest patients who achieve return of spontaneous circulation, continue warming to 32-34°C and maintain according to standard post-arrest guidelines for therapeutic hypothermia if indicated. 1

Critical Monitoring During Rewarming

Cardiac Complications

• Continuously monitor for cardiac arrhythmias, particularly bradycardia and ventricular fibrillation. 2, 3, 6
• Bradycardia may actually be physiologically beneficial during hypothermia and does not necessarily require treatment. 3
• Monitor for signs of rewarming shock and hemodynamic instability. 2, 3

Metabolic and Hematologic Complications

• Monitor for coagulopathy, as each 1°C drop in temperature causes a 10% drop in coagulation factor function. 6
• Do not assume coagulopathy is absent based on standard laboratory tests run at 37°C, as body temperatures below 34°C compromise blood coagulation that may not be reflected in these tests. 6
• Watch for electrolyte abnormalities, particularly post-dialysis hypophosphatemia and rebound hyperkalemia if hemodialysis was used. 8
• Monitor for hyperglycemia, especially in diabetic patients. 2, 3
• Assess for rhabdomyolysis and myoglobinuria. 4, 5

Other Complications

• Monitor for rebound hyperthermia after rewarming. 3
• Watch for burns from improper use of active external rewarming devices. 1, 2, 3
• Assess for pneumonia, pulmonary edema, disseminated intravascular thrombosis, and seizures in the post-resuscitation period. 5

Critical Pitfalls to Avoid

Do not use cold IV fluid boluses for treating accidental hypothermia, as this is only indicated for therapeutic hypothermia in normothermic patients. 3, 6

Do not rewarm above 37°C, as this is consistently associated with poor outcomes and increased mortality. 2, 3, 6

Do not rely on passive rewarming alone for temperatures below 32°C, as active measures are required at this severity. 3

Do not assume the patient is dead based on appearance alone, as severely hypothermic patients may appear lifeless but can be successfully resuscitated with aggressive management. 1, 5

Special Population: Trauma Patients

Aggressively correct hypothermia in trauma patients without traumatic brain injury (TBI), as hypothermia represents an independent risk factor for bleeding, coagulopathy, and death. 1, 6

For patients with isolated TBI after hemorrhage has been controlled, consider prolonged hypothermia at 33-35°C for ≥48 hours, as long-term cooling shows mortality benefit and improved neurologic outcomes. 6

Emphasis should be on prevention first and treatment second in trauma, as it becomes progressively more difficult to rewarm once considerable heat is lost. 1