What is the recommended approach to resuscitate a patient with severe hypothermia (core temperature <30 °C), including airway management, breathing support, circulation (chest compressions), defibrillation, drug dosing, and active rewarming methods?

Resuscitation in Hypothermia

Core Principle: "They're Not Dead Until They're Warm and Dead"

Full resuscitative measures, including CPR and extracorporeal rewarming when available, must be initiated immediately for all hypothermic patients without signs of obvious death (rigor mortis or nonsurvivable traumatic injury), and resuscitation should continue throughout rewarming until core temperature reaches at least 32-34°C. 1

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Immediate Assessment and Stabilization

Temperature Measurement

• Measure core temperature using esophageal or bladder probes capable of reading below 35°C—these provide the most accurate readings 2
• Oral probes placed in the sublingual pouch are acceptable alternatives 2
• Avoid axillary measurements as they read 1.5-1.9°C below actual core temperature and will lead to incorrect treatment decisions 2
• Monitor core temperature every 5-15 minutes depending on severity 2

Prevent Further Heat Loss (All Patients)

• Remove all wet clothing immediately 1, 3
• Move to warm environment and shield from wind 2, 3
• Insulate from ground and cover head/neck 2, 3
• Apply at least two dry insulating blankets 3

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Airway Management

Proceed with advanced airway insertion according to standard ACLS guidelines—do not delay essential airway management due to concerns about cardiac irritability. 1, 2

• Intubation enables effective ventilation with warm, humidified oxygen and reduces aspiration risk 1
• Gentle handling is critical in moderate-to-severe hypothermia to avoid triggering ventricular fibrillation 2, 3

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Breathing Support

• Provide warm, humidified oxygen to all hypothermic patients 1, 2
• If the patient is not breathing, start rescue breathing immediately 1
• Do not overventilate—maintain normal ventilation rates 4
• Warm humidified oxygen serves as both respiratory support and a core rewarming technique 1, 2

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Circulation: CPR Considerations

When to Start CPR

• Begin CPR immediately if the hypothermic patient has no signs of life, regardless of how cold they appear 1
• Severe hypothermia causes marked decrease in heart rate and respiratory rate, making it difficult to determine true cardiac arrest—take extra time to check for life signs before initiating CPR 1, 4
• Pulse and respiratory rates may be extremely slow or difficult to detect, and ECG may show asystole even with a perfusing rhythm 1

CPR Technique

• Perform chest compressions at regular normothermic rates 4
• Continue CPR throughout rewarming until the patient is rewarmed to at least 32-34°C or shows return of spontaneous circulation 1
• Use mechanical CPR devices when available, especially for prolonged rescue or difficult evacuations 5, 6

Intermittent CPR (Only When Continuous CPR Impossible)

If continuous or mechanical CPR is not feasible during difficult evacuations:

• Core temperature <28°C: alternate 5 minutes CPR with ≤5 minutes without CPR 5
• Core temperature <20°C: alternate 5 minutes CPR with ≤10 minutes without CPR 5
• Continuous CPR remains the standard—intermittent CPR should only be used when continuous CPR is truly impossible 5, 6

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Defibrillation

Attempt defibrillation immediately for ventricular fibrillation or ventricular tachycardia, regardless of core temperature, and continue according to standard BLS algorithms concurrent with rewarming. 1

Key Evidence Challenging Old Dogma

• Previous guidelines suggested withholding defibrillation below 30°C, but animal studies show better defibrillation response at 30°C than in normothermic arrest 1
• A case report documents successful defibrillation at 18.2°C with good neurological outcome 7
• Do not limit defibrillation attempts to three shocks—continue standard BLS algorithm while rewarming 1
• Success is more likely once core temperature reaches 30-34°C, but attempts should not be withheld at lower temperatures 8, 3

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Drug Administration

It may be reasonable to administer epinephrine during cardiac arrest according to standard ACLS algorithms concurrent with rewarming strategies. 1

Evidence Supporting Vasopressor Use

• Animal meta-analysis shows vasopressors (epinephrine or vasopressin) increase return of spontaneous circulation to 62% versus 17% with placebo in hypothermic arrest 1
• This challenges conventional wisdom that suggested withholding IV drugs below 30°C 1
• Drug metabolism is reduced below 30°C with theoretical concern for toxic accumulation, but emerging evidence supports their use 1, 8

Antiarrhythmic Drugs

• No demonstrated benefit for antiarrhythmic medications in hypothermic arrest 1
• Focus on defibrillation and vasopressors rather than antiarrhythmics 1

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Active Rewarming Methods by Severity

Mild Hypothermia (32-35°C)

• Passive rewarming with blankets plus active external methods 1, 3
• Forced-air warming blankets, heating pads, radiant heaters 2, 3
• High-calorie foods or warm drinks if alert and able to swallow 2, 3
• Monitor continuously for deterioration 2

Moderate Hypothermia (28-32°C)

• Medical emergency—activate emergency response system 2, 3
• Aggressive active external rewarming with forced-air warming blankets (increases rewarming rate to ~2.4°C/hour versus 1.4°C/hour with passive blankets) 2, 3
• Warmed intravenous isotonic crystalloid 2
• Warm humidified oxygen 2
• Handle gently to avoid triggering arrhythmias 2, 3

Severe/Profound Hypothermia (<28°C)

Cardiopulmonary bypass (ECMO) provides the most rapid and effective rewarming for severely hypothermic patients, especially those in cardiac arrest, and should be prioritized. 2, 8

• Transport directly to an ECLS/ECMO-capable center when feasible—this may necessitate earlier transport than in normothermic cardiac arrest 8
• Alternative invasive core rewarming techniques when ECMO unavailable: 1, 2
  • Body-cavity lavage with warmed fluids (thoracic, intraperitoneal)
  • Hemodialysis
  • Warm-water lavage of thoracic cavity
• Do not delay transport to an ECMO center while attempting prolonged field resuscitation 8
• Passive and external rewarming methods are inadequate for severe hypothermia with cardiac arrest 8

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Rewarming Targets and Endpoints

• Target minimum core temperature of 36°C before considering the patient stable or transferring between units 2, 3
• Cease rewarming at 37°C—higher temperatures are associated with poor outcomes and increased mortality 2, 3
• After return of spontaneous circulation, continue warming to 32-34°C and follow standard post-arrest care 1, 2

Expected Rewarming Rates

• Conservative methods: ~1.09°C/hour 3
• Forced-air warming: ~2.4°C/hour 2, 3
• With shivering present: up to 3.6°C/hour 3
• ECMO/cardiopulmonary bypass: most rapid, far exceeding other methods 8

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When to Stop Resuscitation

Do not stop resuscitation until the patient has been rewarmed to at least 32-34°C AND remains in refractory cardiac arrest despite appropriate ACLS interventions. 8

Only Stop Resuscitation When:

• Obvious signs of death are present (rigor mortis) 1, 8
• Nonsurvivable traumatic injury exists (decapitation, massive crush injuries) 1, 8
• Patient has been successfully rewarmed to normothermia (≥32-34°C) and remains in refractory cardiac arrest despite appropriate ACLS 8

Critical Principle

• Victims of accidental hypothermia should not be considered dead before rewarming unless there are signs of obvious death 1, 8
• Full neurological recovery is possible even with prolonged cardiac arrest if the brain was severely hypothermic before arrest occurred 5, 6
• Hypothermic patients have higher chances of survival and good neurological outcome than normothermic patients for witnessed, unwitnessed, and asystolic cardiac arrest 6

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Monitoring During Resuscitation and Rewarming

• Continuous cardiac monitoring for arrhythmias, particularly bradycardia (which may be physiologically beneficial) 2
• Monitor for complications: 2, 3
  • Rewarming shock and hemodynamic instability
  • Coagulopathy
  • Electrolyte abnormalities (especially hyperkalemia, which typically corrects with rewarming) 8
  • Hyperglycemia
  • Rebound hyperthermia
  • Burns from improper use of warming devices

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Critical Pitfalls to Avoid

• Never delay essential airway management or vascular access due to concerns about cardiac irritability 2
• Never handle moderate-to-severe hypothermia patients roughly—this can precipitate fatal arrhythmias 2, 3
• Never rely solely on clinical appearance for severity classification—core temperature measurement is mandatory 2
• Never use cold IV fluid boluses for treating accidental hypothermia (only indicated for therapeutic hypothermia) 2, 3
• Never rewarm above 37°C—associated with poor outcomes 2, 3
• Never rely solely on peripheral warming methods in severe hypothermic arrest—these patients need extracorporeal rewarming 8
• Never stop resuscitation prematurely—continue until rewarmed to at least 32-34°C 1, 8