What is the recommended duration and management of therapeutic hypothermia (TH) post cardiac arrest?

Duration of Therapeutic Hypothermia Post-Cardiac Arrest

For comatose patients after cardiac arrest, maintain targeted temperature management for at least 24 hours after achieving target temperature, followed by active fever prevention (temperature ≤37.5°C) for 36 to 72 hours. 1

Core Duration Recommendation

The 2024 International Consensus on Cardiopulmonary Resuscitation provides the most current guidance, recommending active fever prevention for 36 to 72 hours in post-cardiac arrest patients who remain comatose (good practice statement). 1 This represents a shift from the prior 2022 recommendation of "at least 72 hours" to a more flexible range of 36-72 hours. 1

Initial Temperature Control Phase

• Maintain targeted temperature management for a minimum of 24 hours after achieving the target temperature range (32°C-36°C). 1, 2
• This 24-hour minimum is based on protocols used in the two largest randomized controlled trials that demonstrated benefit. 1, 2
• The landmark TTM trial used 28 hours at target temperature followed by slow rewarming, totaling 36 hours of temperature control. 2

Evidence Base for Duration

The task force acknowledged that no difference in outcomes was found when comparing different durations of temperature control:

• One trial showed no difference between 24 and 48 hours of hypothermia. 1
• Another trial found no difference between 12-24 hours and 36 hours of hypothermia. 1
• An additional trial comparing 36 hours versus 72 hours of temperature control found no difference in survival or neurological outcomes at 90 days. 1
• Two observational studies found no difference in mortality or neurologic outcome when comparing 24 hours versus 72 hours of hypothermia. 1, 2

Temperature Management Strategy

Target Temperature Selection

• Target a constant temperature between 32°C and 36°C for patients in whom temperature control is used. 1
• The 2024 guidelines suggest actively preventing fever by targeting temperature ≤37.5°C for patients who remain comatose after return of spontaneous circulation (ROSC). 1
• Whether subpopulations may benefit from lower temperatures (32°C-34°C) versus higher temperatures (36°C) remains uncertain. 1

Rewarming Protocol

• Rewarming should be gradual at approximately 0.25-0.5°C per hour to avoid rebound hyperthermia and secondary brain injury. 2
• Active rapid rewarming is generally unwarranted and should be avoided based on expert opinion. 1
• After the initial temperature control period, strict fever prevention should continue, maintaining temperature <37.5°C. 2

Implementation Considerations

Monitoring and Equipment

• Use a temperature control device with a feedback system based on continuous temperature monitoring to maintain the target temperature (good practice statement). 1
• Both surface and endovascular temperature control techniques are acceptable when temperature control is used. 1

Prehospital Cooling

• Do NOT routinely use prehospital cooling with rapid infusion of large volumes of cold intravenous fluid immediately after ROSC (strong recommendation, moderate-certainty evidence). 1
• Multiple randomized trials found no benefit from prehospital cooling, and one trial found increased pulmonary edema and rearrest with rapid infusion of 2L of cold fluids. 1

Clinical Rationale

Temperature sensitivity of the brain after cardiac arrest may persist as long as coma is present, making the upper limit of beneficial temperature management duration unknown. 1, 2 The 24-hour minimum is well-established, but extending beyond this timeframe has not demonstrated proven benefit and may increase complications. 2

Common Pitfalls to Avoid

• Do not allow patients to warm above 36°C during the initial control period, as this would be more akin to the control groups in earlier trials and not consistent with current recommendations. 1
• Avoid active rapid rewarming after the temperature control period ends. 1
• Monitor for complications including hyperglycemia, hypokalemia, arrhythmias, and QT prolongation, especially with concurrent use of QT-prolonging drugs. 3, 4
• Do not delay coronary angiography or percutaneous coronary intervention due to hypothermia, as these procedures are feasible and safe during temperature management. 3