Neurological Pupil Index and Pupillary Light Reflex by Pupillometry Predict Outcome Early After Cardiac Arrest

The absence of the pupillary light reflex (PLR) 3 days after cardiac arrest predicts poor outcome, but quantitative PLR assessment with pupillometry early after recovery of spontaneous circulation (ROSC) and throughout targeted temperature management (TTM) has rarely been evaluated.

Fifty-five adult patients treated with TTM with available pupillometry data from the NeurOptics NPi-200 were studied. Discharge outcome was classified good if the cerebral performance category score was 1-2, poor if 3-5. Pupil size, PLR percent constriction (%PLR), and constriction velocity (CV) were determined at TTM start and 6 (± 2)-h post-ROSC ("early"), and throughout TTM using data from the worst eye at each assessment. The Neurological Pupil index (NPi) was also determined at each pupil assessment; the NPi is scored from 0 (nonreactive) to 5 (brisk) with values < 3 considered sluggish or abnormal. Prognostic performance to predict poor outcome was assessed with receiver operator characteristic curves.

All nine patients with ≥ 1 nonreactive pupil (NPi = 0) within 6 (± 2) h after ROSC died, and 12/14 (86%) with sluggish pupils (0 < NPi < 3) had poor outcomes. 15/29 (52%) patients with normal pupil reactivity (NPi ≥ 3) had poor outcomes, four survived with cerebral performance category = 3, three died of cardiac causes, and eight died of neurologic causes. During TTM, 20/21 (95%) patients with nonreactive pupils had poor outcomes, 9/14 (64%) of patients with sluggish pupils had poor outcomes, and 9/20 (45%) with normal pupil reactivity had poor outcomes. Pupil size did not predict outcome, but NPi (AUC = 0.72 [0.59-0.86], p < 0.001), %PLR (AUC = 0.75 [0.62-0.88], p < 0.001) and CV (AUC = 0.78 [0.66-0.91], p < 0.001) at 6 h predicted poor outcome. When nonreactive pupils were first detected, 75% were < 5 mm.

Very early after resuscitation from cardiac arrest, abnormal Neurological Pupil index and pupillary light reflex measurements by pupillometer are predictive of poor outcome, and are not usually associated with dilated pupils.