Outcome pRognostication of Acute Brain Injury With the NeuroloGical Pupil

Introduction Pupillary examination, and in particular pupillary light reactivity (PLR), is fundamental for intensive care unit (ICU) monitoring and follow-up of patients with acute brain injury (ABI), and has both diagnostic and prognostic values. Secondary cerebral insults, e.g. elevated intracranial pressure (ICP) may alter midbrain function and cause abnormalities in pupil size, symmetry and PLR. Sustained or newfound pupillary abnormalities are associated with a worse outcome, and indeed PLR is a robust validated predictor in several prognostic models, such as the CRASH (Corticosteroid Randomization after Significant Head Injury) and the IMPACT (International Mission for Prognosis and Analysis of Clinical Trials) scores. In current clinical practice however, pupillary examination is performed using a manual, hand-held light source (e.g. pen torch), implying that the evaluation of pupillary size and reactivity remains essentially based on a visual qualitative assessment. This traditional approach has several limitations, such as limited precision (especially in patients with small pupil size), significant intra- and inter-observer variability, differences in ambient light exposure between measurements, or the technique used to direct the stimulus (i.e. intensity, proximity, duration and orientation of the light source).

The use of quantitative, automated, infrared technology for pupillary examination has long been used in ophthalmology and anesthesiology research. Its interest in neurocritical care has progressively grown, in parallel with the advancements in device technology. In this regard, the use of the noninvasive NPi®-200 pupillometer (Neuroptics, Laguna Hills, CA, USA) allows the measurement of a series of dynamic pupillary variables (including the percentage pupillary constriction, latency, constriction velocity, and dilation velocity), which can be integrated into an algorithm, to compute the Neurological Pupil index (NPi). The NPi is a proprietary scalar index with values between 0 and 5 (with a 0.1 decimal precision), an NPi value < 3 indicating an abnormal pupillary reactivity. Importantly, the NPi is not influenced by sedation-analgesia, at the doses used in neurocritical care practice, and by mild hypothermia.

Preliminary single-center data recently demonstrated that abnormal NPi is associated with worse outcome in patients with traumatic and hemorrhagic ABI, and can be a useful adjunct for ICP monitoring and therapy. There is currently a great need for quantitative tools to predict early prognostication in ABI patients, and the NPi appears of potential great value. For this purpose, large multicenter studies are required. The Investigators recently conducted an international multicenter study that demonstrated the prognostic value of NPi in the setting of early prognostication of ABI following cardiac arrest. Here, the Investigators aim at evaluating the prognostic value of the NPi in patients with ABI following traumatic brain injury (TBI), aneurysmal subarachnoid hemorrhage (SAH) or intracerebral hemorrhage (ICH) at risk of secondary ICP elevation.

Research questions

The Investigators hypothesize that: