Therapeutic Hypothermia Protocol
Patient Selection
Comatose adult patients (not responding meaningfully to verbal commands) with return of spontaneous circulation (ROSC) after out-of-hospital ventricular fibrillation cardiac arrest should be cooled to 32-34°C for 12-24 hours. 1, 2
Primary Indications:
- Comatose state defined as Glasgow Coma Scale ≤8 or inability to follow verbal commands after ROSC 2, 3
- Out-of-hospital VF/pulseless VT cardiac arrest (strongest evidence) 1, 3
Extended Indications (weaker evidence but reasonable):
- Non-shockable rhythms (asystole, PEA) - may also benefit 1, 2
- In-hospital cardiac arrest of cardiac etiology 1, 3
Absolute Contraindications:
- Severe cardiogenic shock (SBP <90 mmHg despite vasopressors) 3
- Life-threatening arrhythmias 3
- Cardiac arrest from clearly non-cardiac causes (head trauma, drug overdose, stroke) 3
- Primary coagulopathy 3
Induction Methods
Initial Cooling - Choose One or Combine:
Rapid infusion of ice-cold IV fluids is the fastest, simplest initial method: 1, 2
- 30 mL/kg of ice-cold 0.9% saline or Ringer's lactate administered rapidly 1, 2
- Can lower core temperature by up to 1.5°C 1
- Can be initiated in the prehospital setting 1
- Additional cooling methods will be required to maintain target temperature 1
Alternative/Adjunctive Methods: 1
- Ice packs applied to groin, axillae, neck (sometimes with wet towels) 1
- Water-circulating or air-circulating cooling blankets 1
- Intravascular heat exchange catheters (most precise control) 1
- Cooling helmets or caps (feasible for prehospital use) 4
Target Temperature & Duration
Target: 32-34°C maintained for 12-24 hours 1, 2
Timing Considerations:
- Initiate cooling as rapidly as possible after ROSC - ideally within minutes to hours 1, 3
- While earlier is theoretically better, registry data showed median cooling initiation at 90 minutes (IQR 60-165 min) was not independently associated with worse outcomes 1
- Target temperature should ideally be reached within 4 hours of ROSC 3
- Acceptable delay up to 4-6 hours after ROSC still shows benefit 3
Maintenance Phase
Temperature Monitoring:
- Continuous core temperature monitoring is essential (esophageal, bladder, or rectal probe preferred over tympanic) 5, 6
- Maintain strict temperature control between 32-34°C 1, 2, 5
Shivering Management (Critical):
- Shivering must be prevented as it generates heat and defeats cooling 5, 6
- First-line: Benzodiazepines (used by 46% of practitioners) 7
- Consider neuromuscular blocking agents if shivering persists despite sedation 6
- Maintain adequate sedation and analgesia throughout cooling period 5, 6
Expected Complications to Monitor:
- Hyperglycemia - monitor glucose closely 2
- Hypokalemia - check and replace electrolytes frequently 2
- Cardiac arrhythmias (usually bradycardia) 2, 6
- Coagulopathy - monitor coagulation parameters 6
- Pneumonia and sepsis - increased infection risk 6
Rewarming Protocol
Rewarming must be slow and controlled: 5, 6
- Passive rewarming is preferred over active rapid rewarming 2
- Target rewarming rate: reach 36°C over at least 8 hours (approximately 0.25-0.5°C per hour) 6
- Once temperature exceeds 35°C, sedation, analgesia, and paralysis can be discontinued 6
- Avoid hyperthermia in the post-resuscitation period - treat any fever >37.6°C aggressively 1
Special Considerations
Concurrent PCI:
Do not delay percutaneous coronary intervention for therapeutic hypothermia 1, 2
- The combination of therapeutic hypothermia and PCI is feasible and safe 1, 2, 3
- Cooling can be initiated before, during, or after PCI 3
- Patients with STEMI requiring primary PCI should receive therapeutic hypothermia as soon as possible without delaying catheterization 3
Practical Implementation:
- An established institutional protocol with standardized order sets improves consistency and outcomes 5, 7
- Average time to target temperature in practice is approximately 95 minutes when using commercial cooling devices 7
- Despite guidelines, only 69% of surveyed emergency departments use therapeutic hypothermia, with barriers cited as cost, implementation difficulty, and perceived insufficient evidence 7
Expected Outcomes
Number Needed to Treat: 6 patients to save one life 6