Head Kinematics, Blood Biomarkers and Histology in Large Animal Models of Traumatic Brain Injury and Hemorrhagic Shock.

Traumatic brain injury (TBI) and severe blood loss resulting in hemorrhagic shock (HS) are each leading causes of mortality and morbidity worldwide, and present additional treatment considerations when comorbid (TBI+HS) due to competing pathophysiological responses. The current study rigorously quantified injury biomechanics with high precision sensors and examined whether blood-based surrogate markers were altered in general trauma as well as post-neurotrauma. Eighty-nine sexually mature male and female Yucatan swine were subjected to a closed-head TBI+HS (40% of circulating blood volume; N=68), HS only (N=9), or sham trauma (N=12). Markers of systemic (e.g., glucose, lactate) and neural functioning were obtained at baseline, 35 and 295 minutes post-trauma. Opposite and approximately two-fold differences existed for both magnitude (device>head) and duration (head>device) of quantified injury biomechanics. Circulating levels of neurofilament light chain (NFL), glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) demonstrated differential sensitivity for both general trauma (HS) and neurotrauma (TBI+HS) relative to shams in a temporally dynamic fashion. GFAP and NFL were both strongly associated with changes in systemic markers during general trauma, and exhibited consistent time-dependent changes in individual sham animals. Finally, circulating GFAP was associated with histopathological markers of diffuse axonal injury and blood-brain barrier breach, as well as variations in device kinematics following TBI+HS. Current findings therefore highlight the need to directly quantify injury biomechanics with head mounted sensors and suggest that GFAP, NFL and UCH-L1 are sensitive to multiple forms of trauma rather than having a single pathological indication (e.g., GFAP=astrogliosis).