What are the appropriate treatments for hypothermia based on its severity?

Treatment of Hypothermia Based on Severity

Treat hypothermia using a severity-based algorithm: passive rewarming for mild cases (32-35°C), active external rewarming for moderate cases (28-32°C), and active core rewarming for severe cases (<28°C), targeting normothermia at 36-37°C. 1, 2

Immediate Universal Interventions (All Severities)

Before addressing specific severity levels, implement these critical first steps for every hypothermic patient:

• Remove all wet clothing immediately and move the patient from the cold environment to a warm one 3, 1, 2
• Insulate from the ground and cover the head and neck, as these are major sources of heat loss 3, 1
• Shield from wind and apply at least two dry insulating blankets 1, 4
• Monitor core temperature using oral or esophageal probes every 5-15 minutes depending on severity—avoid axillary measurements as they read 1.5-1.9°C below actual core temperature 1, 4, 2

Critical pitfall: Most trauma patients (73%) are already hypothermic at first measurement on scene, and temperature drops rapidly at -1.7°C/hour without intervention 5. Early recognition and prevention of further heat loss is paramount.

Mild Hypothermia (32-35°C)

Use passive rewarming techniques as the primary approach for patients who are alert and shivering 3, 1, 4:

• Allow the body to rewarm itself naturally with blankets and increased environmental temperature (expected rate: 1.2°C/hour, up to 3.6°C/hour if shivering) 3, 1
• Provide high-calorie foods or warm drinks if the patient is alert and able to swallow safely, as shivering increases metabolic rate 5-6 times and requires substantial calorie expenditure 3, 1
• Monitor for signs of deterioration including altered mental status, decreased responsiveness, or cessation of shivering 3, 4

Important caveat: If the patient shows altered responsiveness or inability to participate in removing wet clothing, escalate to moderate hypothermia protocols even if temperature is in the mild range 3.

Moderate Hypothermia (28-32°C)

Implement active external rewarming methods in addition to all measures for mild hypothermia 1, 4, 2:

• Apply forced-air warming blankets as the primary active rewarming method, which increases rewarming rates to approximately 2.4°C/hour compared to 1.4°C/hour with passive blankets alone 1, 4, 2
• Use heating pads, radiant heaters, or water-circulating warming blankets as alternatives 4
• Administer warmed intravenous fluids (not cold IV boluses, which are contraindicated in accidental hypothermia) 1, 4, 2
• Provide humidified, warmed oxygen 4, 6

Critical monitoring: This is a medical emergency requiring continuous cardiac monitoring for arrhythmias, particularly bradycardia, and vigilance for coagulopathy, as each 1°C drop causes a 10% decrease in coagulation factor function 3, 1, 2.

Common pitfall: Do not cut off damp clothing in exposed environments—chemical heat packs work across damp (but not saturated) clothing, so only remove saturated clothing in a protected environment 3.

Severe/Profound Hypothermia (<28°C)

Activate the emergency response system immediately and consider active core rewarming methods while continuing all measures for moderate hypothermia 3, 1, 4:

• Handle the patient extremely gently to avoid triggering ventricular fibrillation or other lethal arrhythmias 1, 4, 7
• Consider peritoneal lavage with warmed fluids or body cavity lavage 1, 2, 8
• Transfer directly to an ECLS (extracorporeal life support) center if the patient has cardiac arrest, ventricular arrhythmia, systolic blood pressure <90 mmHg, or temperature <28°C 7
• Provide continuous CPR during transport if arrested—mechanical CPR devices are helpful for prolonged or difficult terrain transport 7

Critical principle: A deeply hypothermic person may appear dead but can still be resuscitated if treated correctly, with survival rates approaching 100% with ECLS for hypothermic cardiac arrest 7.

Rewarming Targets and Endpoints

Target a minimum core temperature of 36°C before considering the patient stable or transferring between units 1, 4, 2:

• Cease rewarming at 37°C—higher temperatures are associated with poor outcomes and increased mortality 1, 4, 2
• Do not use rapid active warming in post-cardiac arrest patients; maintain temperature between 32-36°C 1

Special Considerations for Trauma Patients

In trauma, hypothermia independently increases mortality by >80% when temperature drops below 34°C and dramatically worsens coagulopathy and bleeding 3, 2:

• Target normothermia (36-37°C) aggressively in trauma patients to create optimal conditions for coagulation 3, 2
• Remove wet clothing, increase ambient temperature, use forced-air warming, warm fluid therapy, and in extreme cases extracorporeal rewarming devices 3
• For isolated traumatic brain injury after hemorrhage control, consider prolonged hypothermia at 33-35°C for ≥48 hours, as long-term cooling shows mortality benefit compared to short-term cooling 2

Major pitfall: Standard coagulation tests (PT/APTT) run at 37°C will not detect coagulopathy present at the patient's actual low temperature—do not assume coagulopathy is absent based on these results 3, 2.

Cardiac Arrest Management

If the hypothermic patient has no signs of life, begin CPR immediately without delay 1, 6:

• Attempt defibrillation if ventricular tachycardia or ventricular fibrillation is present 1
• Consider vasopressor medications (epinephrine or vasopressin) as they increase rates of return of spontaneous circulation 1
• Continue CPR during transport to an ECLS center—do not terminate resuscitation prematurely, as patients with core temperatures <20-25°C may still be viable 6, 7

Monitoring for Complications During Rewarming

Watch continuously for these complications that can worsen outcomes 1, 4, 2:

• Cardiac arrhythmias (bradycardia may actually be physiologically beneficial and should not be aggressively treated) 4
• Rewarming shock and hemodynamic instability 1, 4
• Coagulopathy and ongoing bleeding 3, 2
• Electrolyte abnormalities and hyperglycemia (particularly in diabetic patients) 1, 4
• Rebound hyperthermia 4
• Burns from improper use of active external rewarming devices 1, 4
• Post-resuscitation complications including pneumonia, pulmonary edema, myoglobinuria, and seizures 6