What is the role of targeted temperature management (TTM) in patients who have suffered cardiac arrest?

Targeted Temperature Management in Post-Cardiac Arrest Care

Targeted temperature management (TTM) should be implemented for all comatose patients following return of spontaneous circulation (ROSC) after cardiac arrest, with a target temperature between 32-36°C maintained for at least 24 hours. 1

Patient Selection and Evidence Base

TTM effectiveness varies based on arrest characteristics:

Out-of-Hospital Cardiac Arrest (OHCA)

• Shockable initial rhythm (VF/pVT):

  • Strong recommendation for TTM (32-36°C)
  • Highest quality evidence supports use in this population
  • Associated with improved neurologic outcomes at 6 months (RR 1.4; 95% CI 1.08-1.81) and improved survival to hospital discharge 1

• Non-shockable initial rhythm (PEA/asystole):

  • Weak recommendation for TTM
  • Lower quality evidence, but still suggested given poor prognosis and lack of therapeutic alternatives 1
  • Some evidence shows potential mortality benefit at 6 months (OR 0.56; 95% CI 0.34-0.93) 1

In-Hospital Cardiac Arrest (IHCA)

• Weak recommendation for TTM regardless of initial rhythm 1
• Limited evidence but suggested based on pathophysiological benefits 1

Implementation Protocol

1. Target Temperature:

   • Maintain constant temperature between 32-36°C 1
   • No clear evidence that 32-34°C is superior to 36°C for overall outcomes 1
   • Select temperature within this range based on individual patient factors

2. Duration:

   • Maintain target temperature for at least 24 hours 1
   • Previous landmark trials used 12-28 hours of cooling 1

3. Timing:

   • Initiate TTM as soon as possible after ROSC
   • Avoid delays in implementation

4. Post-TTM Management:

   • Prevent fever (<37.5°C) for at least 72 hours after ROSC 1
   • Gradual rewarming after TTM period

Prognostic Factors Affecting Outcomes with TTM

Several factors are associated with neurologic outcomes in patients receiving TTM 2:

• Favorable factors:

  • Initial shockable rhythm
  • Witnessed arrest
  • Bystander CPR
  • Lower total epinephrine dose during resuscitation
  • Pre-arrest good neurological status

• Unfavorable factors:

  • Advanced age
  • Comorbidities (diabetes, chronic kidney disease, malignancy)
  • Non-shockable rhythm
  • Unwitnessed arrest

Common Pitfalls and Caveats

1. Temperature Control in Control Groups:

   • Fever prevention is crucial even if not using full TTM protocol
   • Hyperthermia is detrimental to neurologic recovery

2. Hemodynamic Management:

   • TTM at 33°C may require increased vasopressor support compared to 36°C 1
   • Bradycardia during mild hypothermia may be beneficial and associated with good outcomes 1

3. Monitoring and Complications:

   • Monitor for shivering and treat appropriately
   • Watch for electrolyte abnormalities, particularly hypokalemia during rewarming
   • Increased infection risk with deeper hypothermia

4. Prognostication Timing:

   • Delay neurologic prognostication until at least 72 hours after ROSC in patients treated with TTM
   • TTM may alter the timeline for reliable prognostic indicators

TTM remains the only post-resuscitation intervention shown to improve survival with good neurologic outcome, particularly in OHCA with shockable rhythms. Despite some conflicting evidence regarding optimal temperature targets, the evidence supports implementing TTM as part of a comprehensive post-cardiac arrest care bundle to improve morbidity, mortality, and quality of life outcomes.