Anoxic-ischemic encephalopathy: clinical and electrophysiological associations with outcome

Prognostic determination of patients in coma after resuscitation from cardiac arrest is both common and difficult. We explored clinical and electrophysiological testing to determine their associations with favorable and poor outcomes.

We studied 75 comatose patients resuscitated from cardiac arrest, excluding those who were brain dead or continuously sedated; none received hypothermia therapy. Clinical examinations were performed on day 1.

The following proportions recovered awareness: 2 of 18 patients with absent pupillary reflexes; 18 of 57 with preserved pupillary reflexes (p = 0.08); 2 of 32 with absent corneal reflexes; 16 of 43 with preserved corneal reflexes (p = 0.001); 0 of 15 with absent oculovestibular reflexes; and 8 of 29 with preserved oculovestibular reflexes (p < 0.037). Purposeful movements were associated with a high probability of recovery, whereas other categories were unfavorable. Other categories of motor response were associated with an increased proportion of those who died without recovering awareness, but each category had some survivors. Somatosensory evoked potentials (SSEPs) were recorded from 47 patients. One of 21 patients with loss of the N20 component survived, compared with survival of 11 of 26 patients in whom it was present (p = 0.003). All 5 patients with preserved N70 responses recovered awareness in a subgroup of 33 patients. Sixteen of 22 subjects with mild electroencephalogram (EEG) abnormalities recovered consciousness, compared with the survival of 3 of 50 patients with malignant EEG patterns (p = 0.0000001). Combining SSEP with EEG findings produced even greater predictive value.

It seems unlikely that any single test will prove to have 100% predictive value for outcome; further studies combining clinical, EEG, and SSEP testing are warranted.