From the Guidelines
The recommended duration for targeted temperature management (TTM) after cardiac arrest is at least 24 hours. This recommendation is based on the most recent and highest quality evidence available, which suggests that maintaining a constant target temperature between 32°C and 36°C for at least 24 hours can provide neuroprotection and improve outcomes in patients after cardiac arrest 1. The entire TTM protocol includes three phases: induction (cooling to target temperature), maintenance (at least 24 hours at target temperature), and rewarming. During TTM, patients require continuous temperature monitoring, sedation, analgesia, and often neuromuscular blockade to prevent shivering.
- Key considerations for TTM include:
- Target temperature: 32°C to 36°C
- Duration: at least 24 hours
- Monitoring: continuous temperature monitoring, electrolyte abnormalities, arrhythmias, infections, and coagulopathies
- Medications: sedation (e.g., propofol or midazolam), analgesia (e.g., fentanyl or morphine), and neuromuscular blockade (e.g., cisatracurium or rocuronium)
- The 24-hour duration represents a balance between providing neuroprotection through reduced cerebral metabolism and oxygen demand while minimizing potential complications of prolonged hypothermia. Some centers may adjust this duration based on individual patient factors, but at least 24 hours remains the standard recommendation in most post-cardiac arrest care protocols 1.
From the Research
Targeted Temperature Management Duration
The recommended duration for targeted temperature management (TTM) after cardiac arrest is a topic of ongoing research and debate.
- The ERC Guidelines in 2021 recommended TTM for all patients after in- and out-of-hospital cardiac arrest with a target temperature of 32-36 °C for at least 24 hours 2.
- A study published in 2017 found that TTM at 33°C for 48 hours did not significantly improve 6-month neurologic outcome compared with TTM at 33°C for 24 hours 3.
- Another study published in 2019 compared treatment at 33°C and 36°C for 24 hours after out-of-hospital cardiac arrest and found no difference in survival or neurological function between the two groups 4.
- A 2023 study examined adherence to temperature targets and association of time-in-therapeutic range (TTR) with survival and neurologic outcomes, and found that higher TTR was not associated with overall survival, but was associated with favorable neurologic outcome for certain temperature thresholds 5.
Guidelines and Recommendations
- The ERC/ESICM Guidelines updated in 2022 suggest avoiding fever only within the first 72 hours after the event 2.
- The optimal duration of TTM is uncertain, and further research may be warranted to determine the best approach for individual patients 3.
- Current guidelines recommend TTM with a goal temperature of 32 °C-36 °C for at least 24 hours for comatose survivors of out-of-hospital cardiac arrest 5.
Study Findings
- A study published in 2015 found that prehospital hypothermia induced by cold crystalloid infusion does not benefit cardiac arrest patients, and that targeting a temperature of 36°C provides similar results as targeting 33°C 6.
- The TTM2 Trial in 2021 did not show a benefit in survival or neurological outcome in the group of hypothermia at 33°C compared to normothermia 2.