The utility of median somatosensory evoked potentials in anoxic-ischemic coma.

The early recognition of comatose patients with a hopeless prognosis--regardless of how aggressively they are managed--is of utmost importance. Median somatosensory evoked potentials (SSEP) supplement and enhance neurological examination findings in anoxic-ischemic coma and are useful as an early guide in predicting outcome. The key finding is that bilateral absence of cortical evoked potentials reliably predicts unfavorable outcome in comatose patients after cardiac arrest. The author studied 50 comatose patients with preserved brainstem function after cardiac arrest. All 23 patients with bilateral absence of cortical evoked potentials died without awakening. Neuropathological study in seven patients disclosed widespread ischemic changes or frank cortical laminar necrosis. The remaining 27 patients with normal or delayed central conduction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurological deficit or death. Greater use of SSEP in anoxic-ischemic coma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.