Near-Infrared Based Cerebrovascular Reactivity as a Means of Monitoring Cerebral Autoregulation and Predicting Outcome in Moderate/Severe Traumatic Brain Injury: A Pilot Study Protocol and Planned Analyses.

Gomez, Alwyn; Dian, Josh; Froese, Logan; Zeiler, Frederick Adam

BACKGROUND Impaired cerebrovascular reactivity after traumatic brain injury (TBI) in adults is emerging as an important prognostic factor, with strong independent association with 6-month outcomes. To date, it is unknown if impaired cerebrovascular reactivity during the acute phase is associated with ongoing impaired continuously measured cerebrovascular reactivity at in the long-term, and if such measures are associated with clinical phenotype at those points in time. OBJECTIVE Within this manuscript we highlight a prospective pilot study that will preliminarily assess near-infrared spectroscopy (NIRS) derived continuous measures of cerebrovascular reactivity during both acute and long-term phases in adults with TBI. METHODS Over the course of a 2 year period we will recruit up to 80 moderate/severe TBI patients admitted to the intensive care unit (ICU) with an invasive intracranial pressure (ICP) monitoring. These patients will undergo high-frequency data capture of ICP, arterial blood pressure (ABP), and NIRS for the first 5 days of care. Patients will then have 30 minutes of non-invasive NIRS and ABP monitoring in clinic at 3, 6, and 12 months post-injury. Outcomes will be assessed via Glasgow Outcome Scale and Short Form-12 questionnaires. Various relationships between NIRS and ICP derived cerebrovascular reactivity metrics, and associated outcomes, will be assessed using biomedical signal processing techniques and both multi-variate and time-series statistical methodologies. RESULTS This study has currently started recruitment as of the end of February 2020, with data collection ongoing, having enrolled 3 patients at the time of this manuscript composition. Expected duration of data collection will be from February 2020 to January 2022, as per our local research ethics board (REB) approval (B2018:103). Support for this work has been obtained through the National Institutes of Health (NIH), though the National Institute of Neurological Disorders and Stroke (NINDS) (R03NS114335), funded in January 2020. CONCLUSIONS Through application of NIRS technology in the monitoring of TBI patients, we expect to be able to outline core relationships between non-invasively measured aspects of cerebral physiology and both invasive measures, as well as patient outcomes. Documenting these relationships carries the potential to revolutionize the way we monitor TBI patients, moving to more non-invasive techniques. CLINICALTRIAL Not Applicable - not a trial, as deemed by NIH protocol approval.