Neurological pupil index during cardiopulmonary resuscitation is associated with admission to ICU in non-traumatic out-of-hospital cardiac arrest patients

Pupillary light reflex (PLR) is a simple method to assess brainstem function and can be measured objectively and accurately using pupillometry. We sought to investigate the relationship between PLR measured with pupillometry during cardiopulmonary resuscitation (CPR) and early prognosis of out-of-hospital cardiac arrest (OHCA) patients. This study was a single-centre prospective observational study. All OHCA patients who received CPR in the emergency department (ED) from August 2019 to January 2021 were registered, and adult patients whose neurological pupil index (NPi) was measured with an automated pupillometer during CPR in the ED were included. The primary outcome was admission to the intensive care unit (ICU). A total of 109 patients were included, and the mean of the NPi measurements of all the patients was 0.1 +/- 0.7. The mean of the NPi was higher in the patients admitted to the ICU than in those who died in the ED, 0.5 +/- 1.2 vs. 0.0 +/- 0.1 (p = 0.031). Receiver operating characteristic analysis was performed to determine the cut-off value of the NPi, and the optimal cut-off value for ICU admission was 2.0 with sensitivity and specificity 0.769 and 0.652, respectively. Patients with NPi >2.0 showed higher rates of admission to ICU, ICU survival, and good neurologic outcomes at hospital discharge and at 3 months following cardiac arrest, than the patients with NPi <= 2.0. Firth's bias-reduced penalised-likelihood multivariable logistic regression analysis showed that the odds ratio of the group with NPi >2.0 was 14.37 (95% confidence interval, 1.80-179.12), which was an independent variable associated with admission to ICU. NPi of higher than 2.0 is one of the indicators associated with an early favourable outcome of OHCA patients.