Predicting neurological outcome after cardiac arrest

Predicting neurological recovery after successful cardiac arrest resuscitation has always been tricky, with clinical signs on day one being unreliable, but absent pupillary responses or absent or extensor motor responses to painful stimuli being predictive of a poor outcome on day three. However, the use of therapeutic hypothermia, and its frequent associated need for sedation, appear to make even these downstream assessments inclined to give false positive predictions for a poor outcome, potentially resulting in withdrawal of intensive care in patients who may have recovered. A review recommends a multimodal approach to prognostication.

Regarding physical examination, the authors state:

In summary, therapeutic hypothermia and sedation required for induced cooling might delay recovery of motor reactions up to 5–6 days after cardiac arrest. Corneal/ pupillary reflexes and myoclonus are more robust predic- tors of poor outcome after cardiac arrest, but their absence is not an absolute predictor of dismal prognosis

PURPOSE OF REVIEW: Therapeutic hypothermia and aggressive management of postresuscitation disease considerably improved outcome after adult cardiac arrest over the past decade. However, therapeutic hypothermia alters prognostic accuracy. Parameters for outcome prediction, validated by the American Academy of Neurology before the introduction of therapeutic hypothermia, need further update.
RECENT FINDINGS: Therapeutic hypothermia delays the recovery of motor responses and may render clinical evaluation unreliable. Additional modalities are required to predict prognosis after cardiac arrest and therapeutic hypothermia. Electroencephalography (EEG) can be performed during therapeutic hypothermia or shortly thereafter; continuous/reactive EEG background strongly predicts good recovery from cardiac arrest. On the contrary, unreactive/spontaneous burst-suppression EEG pattern, together with absent N20 on somatosensory evoked potentials (SSEP), is almost 100% predictive of irreversible coma. Therapeutic hypothermia alters the predictive value of serum markers of brain injury [neuron-specific enolase (NSE), S-100B]. Good recovery can occur despite NSE levels >33 μg/l, thus this cut-off value should not be used to guide therapy. Diffusion MRI may help predicting long-term neurological sequelae of hypoxic-ischemic encephalopathy.
SUMMARY: Awakening from postanoxic coma is increasingly observed, despite early absence of motor signs and frank elevation of serum markers of brain injury. A new multimodal approach to prognostication is therefore required, which may particularly improve early prediction of favorable clinical evolution after cardiac arrest.
Predicting neurological outcome after cardiac arrest

Curr Opin Crit Care. 2011 Jun;17(3):254-9

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