From the Guidelines
Targeted temperature management (TTM) protocols should be implemented in patients who have experienced cardiac arrest with an initial nonshockable rhythm and remain comatose after return of spontaneous circulation (ROSC), targeting a constant temperature between 32°C and 36°C for 24 hours, as evidenced by the HYPERION trial 1.
Implementation of TTM Protocol
The protocol typically involves cooling the patient to a target temperature between 32-36°C for 24 hours. Implementation begins with rapid cooling using cold IV fluids, surface cooling devices, or intravascular cooling catheters.
- Sedation with propofol or midazolam and neuromuscular blockade with cisatracurium or vecuronium are typically required to prevent shivering.
- Core temperature should be monitored continuously via esophageal, bladder, or intravascular probes.
- After the maintenance period, rewarming should occur slowly at 0.25-0.5°C per hour to avoid rebound hyperthermia, hemodynamic instability, and electrolyte shifts.
Benefits of TTM
TTM is beneficial because it reduces cerebral metabolic demands, decreases free radical production, and mitigates reperfusion injury, ultimately improving neurological outcomes in post-cardiac arrest patients 1.
- The optimal duration for mild induced hypothermia and TTM is currently most commonly used for 24 h, although the TTM trial provided strict normothermia after hypothermia until 72 h after ROSC 1.
- The term targeted temperature management or temperature control is now preferred over the previous term therapeutic hypothermia, as recommended by the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation 1.
Key Considerations
- Whether certain subpopulations of cardiac arrest patients may benefit from lower or higher temperatures remains unknown, and further research may help elucidate this 1.
- TTM is recommended for adults after OHCA with an initial shockable rhythm who remain unresponsive after ROSC, although the evidence for this is low-quality 1.
- The HYPERION trial reinforces the 2015 ILCOR treatment recommendations to consider TTM in patients who remain comatose after resuscitation from either IHCA or OHCA with an initial nonshockable rhythm 1.
From the Research
Implementation of Targeted Temperature Management (TTM) Protocol
Targeted Temperature Management (TTM) protocol for therapeutic hypothermia is implemented in various critical care situations, including:
- Post-cardiac arrest syndrome: TTM is a standard of care in post-cardiac arrest situations, with the aim of preventing hypoxic-ischemic brain damage 2, 3.
- Traumatic brain injury (TBI): TTM is used to reduce intracranial pressure, although its effect on neurologic outcome is still debated 4, 5.
- Meningitis, acute liver failure, and stroke: TTM is considered a therapeutic modality for salvaging neurological tissue viability in these conditions 4.
- Hypoxic ischemic encephalopathy in newborns: Hypothermia is a generally accepted treatment for this condition 4.
Optimal Targeted Core Temperature and Cooling Duration
The optimal targeted core temperature and cooling duration for TTM are still under debate. Studies suggest that:
- A targeted core temperature of 33-34°C may be associated with better neurologic outcomes in patients with moderate-severity postcardiac arrest syndrome 6.
- A targeted core temperature of 35°C may be suitable for patients with post-cardiac arrest syndrome who have a return of spontaneous circulation (ROSC) within 20 minutes 2.
- The cooling duration may vary depending on the patient's condition, with 24 hours being a common duration 2, 3.
Clinical Challenges and Future Directions
The implementation of TTM protocols faces several clinical challenges, including: