In moderate-to-severe traumatic brain injury (TBI), anemia may exacerbate secondary cerebral injury, and patients with multiple trauma may be especially vulnerable to cerebral hypoxia. We conducted a secondary analysis of the HEMOTION trial (liberal transfusion strategy > 10 g/dL vs. restrictive > 7 g/dL), to assess whether multiple trauma modifies the effect of transfusion strategy after moderate-to-severe TBI. We included all HEMOTION trial participants (n = 742) and defined multiple trauma using three definitions: (1) extracranial injury with Injury Severity Score (ISS) > 15; (2) extracranial injury requiring emergency extracranial surgery; (3) spinal injury with neurological deficit. The primary outcome was the 6-month Glasgow Outcome Scale Extended (GOS-E). We tested interactions between transfusion strategy and multiple trauma status using sliding dichotomy and hierarchical Poisson regression, with sensitivity analyses using classical dichotomy (GOS-E ≤ 4) and proportional odds models. Secondary outcomes included mortality, quality of life (EQ-5D-5L, QOLIBRI), functional independence (FIM), and depression (PHQ-9). We found no interaction between multiple trauma status and transfusion strategies on the 6-month GOS-E across all three definitions. The adjusted relative risk (RR) of an unfavourable outcome with the liberal strategy was 0.87 (95

INTRODUCTION: Dysfunctional cerebrovascular reactivity (CVR)/autoregulation contributes to secondary injury following traumatic brain injury (TBI). Currently, monitoring of CVR relies on intracranial pressure (ICP) monitoring and has known thresholds at which outcomes worsen. Interest has shifted to less invasive near infrared spectroscopic (NIRS) regional cerebral oxygen saturation (rSO2) based measures of CVR. However, threshold levels at which outcomes worsen have not yet been determined for these indices. METHODS: A retrospective multi-institutional cohort study utilizing the CAnadian High Resolution TBI (CAHR-TBI) Research Collaborative database was performed. The cohort included TBI patients with ICP, arterial blood pressure (ABP), and rSO2 monitoring treated in adult intensive care units (ICU). COx (using rSO2 and cerebral perfusion pressure) as well as COx_a (using rSO2 and ABP) were calculated for each subject as the rSO2 based indices of CVR. 2 x 2 tables were created grouping patients by alive/dead and favorable/unfavorable outcomes at various thresholds of COx and COx_a as well as rSO2 itself. Chi-square values were calculated and the threshold producing the highest value was identified as providing the best discriminative value. RESULTS: A total of 129 patients were included. For both COx and COx_a an optimal threshold value of 0.2 was identified for both survival (χ 2 = 9.57, p = 0.0020; χ 2 = 13.04, p = 0.0003 respectively) and favorable outcomes (χ 2 = 5.98, p = 0.0145; χ 2 = 8.94, p = 0.0028 respectively) with values above this associated with worse outcomes. Notably, there was no identifiable threshold for raw rSO2 values at which outcomes were identified to worsen. CONCLUSIONS: In this multi-institutional cohort study, COx and COx_a were found to have a uniform threshold of 0.2, above which clinical outcomes worsened. This study lays the groundwork to transition to less invasive means of continuously measuring CVR.

ABSTRACT: In traumatic brain injury (TBI), future integration of multimodal monitoring of cerebral physiology and high-frequency signal processing techniques, with advanced neuroimaging, proteomic and genomic analysis, provides an opportunity to explore the molecular pathways involved in various aspects of cerebral physiologic dysfunction in vivo. The main issue with early and rapid discovery in this field of personalized medicine is the expertise and complexity of data involved. This brief communication highlights the CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Research Collaborative, which has been formed from centers with specific expertise in the area of high-frequency physiologic monitoring/processing, and outlines its objectives.