The NeurO2 Study: Optimal Brain Oxygenation in Neurocritically Ill Patients
The NeurO2 Study: Optimal Brain Oxygenation in Neurocritically Ill Patients
THE PROBLEM
Traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (aSAH) are devastating neurologic events that represent the majority of neurologic intensive care unit (NICU) admissions. Affected patients are often young and have a mortality rate that remains unacceptably high in North America at 20 to 50%. During their stay at NICU, more than 50% of patients with TBI and aSAH develop anemia (hemoglobin <100 g/L), leading to cerebral ischemia and secondary injuries, and associated with worse clinical outcomes.
Tools to reliably quantify cerebral hypoxemic burden are lacking and have been limited historically to sophisticated and inaccessible medical imaging or invasive measures. Near-infrared spectroscopy (NIRS) is an emerging and innovative technology in NICU. Correlation between NIRS value and hemoglobin concentration is well established, but research on the ability of NIRS to successfully detect changes in cerebral oxygenation in response to red blood cells (RBC) transfusion has yielded conflicting results both in NICU and other patient populations. The association of the cerebral hypoxemic burden as measured by NIRS with long-term clinically significant outcomes and whether it could be a trigger for RBC transfusion in addition to hemoglobin levels is yet to be determined.
STUDY HYPOTHESIS
We hypothesize that, in NICU TBI and aSAH adult patients suffering from anemia, the cerebral hypoxemic burden as measured by NIRS is associated with long-term clinical outcomes, affected by RBC transfusion, and thus may serve as a trigger for RBC transfusion in addition to hemoglobin level measurement.
THE PROPOSED STUDY
The NeurO2 Study is nested within 2 large-scale international multicenter CIHR-funded randomized controlled trials, i.e. HEMOTION (n=712; NCT03260478) and SAHaRA (n=740; NCT03309579), examining the effect of two RBC transfusion trigger strategies in NICU patients on long-term neurologic functional outcome in patients with TBI and aSAH, respectively. Study objectives are 1) to evaluate if the cerebral hypoxemic burden as measured non-invasively by NIRS during NICU stay, is associated with the functional neurologic outcome (Glasgow Outcome Scale extended [GOSe]) at 6 months, 2) to determine if the cerebral hypoxemic burden is impacted by RBC transfusions and 3) to determine if the level of response in cerebral hypoxemic burden after RBC transfusion is associated with the 6-month GOSe.
FUNDING
Canadian Institutes of Health Research (CIHR).