An 84-year-old man with coronary artery disease and atrial fibrillation had a ST-segment elevation myocardial infarction that was complicated by a ventricular fibrillation cardiac arrest with 45 minutes of pulselessness. His initial management included evaluation in the cardiac catheterization lab with placement of a bare metal stent into the right coronary artery. He underwent 24 hours of cooling post cardiac arrest, but following this he has had limited neurologic recovery. Post arrest day 6, neurology is consulted.
Which of the following is MOST correct?a. The most accurate prognostic test for poor neurologic outcome is electroencephalography
Correct Answer: D
The extent of brain injury is the key factor for prognostication after cardiac arrest. Clinical examination has been the staple of prognosis— absent pupillary reflexes, absent corneal reflexes, motor response of extensor posturing, or no movement. These findings have come into question in the era of therapeutic cooling. Most importantly, absence of corneal reflexes does not necessarily portent a poor prognosis. Although electroencephalography is for the detection of seizures, the prognostication value has not been validated. Somatosensory evoked potentials (SSEPs) have been studied and the largest study evaluated 407 patients with cardiac arrest, and of the patients with bilaterally absent cortical sensory responses, all had poor neurologic outcome. Pertinent biomarkers include neuron-specific enolase, which was studied in the same SSEP study and levels higher than 33 µg/L predicting a poor outcome, but this study was performed before cooling. Hypothermia can attenuate release of neuron-specific enolase, and there are reports of good outcome with levels greater than 100 µg/L. Although there are limitations to imaging, many use MRI with most useful imaging coming 3 to 5 days post arrest. Common findings are diffuse cortical diffusion restriction and changes in the basal ganglia.
Consideration of Evaluation for Prognosis after Cardiac Arrest:
CT, computed tomography; EEG, electroencephalography; MRI, magnetic resonance imaging; NSE, neurospecific enolase; SSEP, somatosensory evoked potential.