Quantitative pupillometry index to prognosticate neurological outcome in unconscious cardiac arrest patients

The evaluation of pupillary reactivity is crucial in assessing unconscious patients following cardiac arrest (CA). An abnormal Neurological Pupil Index (NPi) is highly specific to predict unfavourable neurological outcome (UO). A new index, the Quantitative Pupillometry Index (QPI) has emerged; however, there are no prognostic data in CA patients. This study compared the prognostic value of NPi and QPI in patients after CA.

This is a prospective observational study conducted at two University hospitals in Belgium and Spain. We collected data from unconsciousness (i.e. Glasgow Coma Scale <9) patients admitted to the Intensive Care Unit after successful resuscitation from CA between March 2022 and October 2024. Measurements of NPi and QPI were performed twice at 24, 48 and 72 h after CA. Follow-up was conducted by telephone interview or follow-up visits; UO was considered as Glasgow-Pittsburgh Cerebral Performance Category 3-5 at 3 months.

193 patients were screened and 111 included in the final analysis. ICU mortality occurred in 69 (62.2%) patients, while 79 (71%) patients had an UO. Patients with UO showed a lower NPi and QPI during the first three days. The QPI showed an increasing positive predictive value over time; at 72 h, a QPI ≤ 2 showed a sensitivity of 60.4 [46.0-73.5]% and a specificity of 100 [87.2-100]% to predict UO, while a NPi ≤ 2 showed a sensitivity of 24.5 [13.8-38.3]% and a specificity of 100 [86.8-100]%.

Abnormal QPI had comparable specificity and a higher sensitivity than NPi in predicting UO at 3 months in comatose patients after CA.