General Considerations

Cardiac arrest remains a major source of death and neurologic disability with less than 10% of patients successfully resuscitated and the majority of survivors left neurologically debilitated. Therapeutic hypothermia is the primary intervention demonstrated to improve neurologic outcome. The neurologic exam and adjunctive tests can inform a patient’s future neurologic prognosis and aid goals of care conversations with the family.

Therapeutic Hypothermia to Improve Neurologic Outcome

See Critical Care: Post-Cardiac Arrest Care

• Intervention: maintain core body temperature at a temperature of 33ºC for 24 hours following cardiac arrest. There is high quality data demonstrating that a target temperature of 36ºC is equivalent to 33ºC but given challenges in achieving consistent temperature control, we have adopted a target temperature of 33ºC at this institution
• Patient population:
  • Most supportive data for benefit is in out-of-hospital ventricular tachyarrhythmias with a number needed to treat of 6 to prevent a poor neurologic outcome (death or severe disability). However, we use therapeutic hypothermia for all patients with cardiac arrest who do not have contraindications to cooling
  • Inclusion criteria for therapeutic hypothermia/targeted temperature management:
    • Non-traumatic cardiac arrest (any rhythm)
    • Age >18 years
    • Time <6h from ROSC
    • Coma (GCS <8) after ROSC not attributed to other causes
    • MAP > 60 mm Hg
  • Exclusion criteria for therapeutic hypothermia/targeted temperature management:
    • Coma prior to arrest OR patient responsive to verbal commands after resuscitation
    • Persistent refractory hypotension (requiring multiple pressors) and/or hypoxemia following resuscitation (though targeted temperature management at 36ºC may be indicated)
    • Severe bleeding/coagulopathy
    • Severe sepsis
    • Pregnancy
    • Cardiac arrest from respiratory failure (relative)
    • Advanced DNR directive

Predictors of Poor Neurologic Outcome  

The following findings are strongly associated with poor neurologic outcome following cardiac arrest:

• Neuro exam: absent pupillary light reflex, absent corneal reflex, extensor motor response to noxious stimuli or absent motor responses to noxious stimuli at 72 hours following resuscitation
  • Adjunctive tests:
  • Somatosensory evoked potentials (SSEPs): measures electrical impulse from the median nerve to the cortex; absent responses at 72 hours after resuscitation are associated with poor outcome
  • EEG: suppression and burst suppression are two malignant findings associated with poor neurologic outcome; presence of background reactivity and variability are favorable signs
  • Serum neuron-specific enolase (NSE): elevated levels > 33 ng/mL at 24-72 hours after resuscitation are associated with poor outcome

Wijdicks et al. Practice parameter: prediction of outcome in comatose survivors after CPR, Neurology 2006;67:203-210

Nielsen et al. Targeted temperature management at 33ºC vs 36 ºC after cardiac arrest, NEJM 2013;369:2197-206

Holzer, M et al. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest.  N Engl J Med 2002;346(8):549-56.

Hernandez, C., & Geocadin, R. (2017). Neurologic Care After Cardiac Arrest. In The Pocket Guide to Neurocritical Care: A concise reference for the evaluation and management of neurologic emergenies (pp. 55-60). Chicago, IL: Neurocritical Care Society