Introduction: Traumatic brain injury (TBI) is the leading cause of injury-related death and disability in children within the United States. Direct mechanical trauma from primary injury can disrupt the blood brain barrier and subsequent biochemical and cellular cascades can impact vascular tone. As endothelial nitric oxide production is diminished, cerebral vasodilation is impaired. Flow-mediated dilation (FMD) is an ultrasound-derived measure that serves as a surrogate for endothelial function in both pediatric and adult studies; however, there are no studies to date that investigate the use of FMD as a marker of endovascular function in children with brain injury. We hypothesize that patients with TBI will have a lower FMD than healthy patients due to the endothelial dysfunction that is sustained at the level of their blood brain barrier in TBI. Methods: A single-center, prospective, observational study used ultrasound to obtain FMD measurements in children with acute TBI in a pediatric trauma center versus healthy age-matched controls. Measurements were obtained within 24 hours of injury. Edge detection software was used to detect changes in the diameter of the brachial artery in response to shear stress, as captured by ultrasound. Reactive hyperemia after vascular occlusion by distal cuff inflation served as the stimulus for FMD. Demographic and clinical data included severity of TBI, mechanism of injury, and functional outcomes. Results: 15 children from 1-18 years of age with mild, moderate, or severe TBI, and 21 healthy age-matched controls were enrolled in this study. The mean age was 9.9 years (SD 3.6). There was a significant decrease in FMD in patients with TBI compared to healthy controls (6.02% vs 7.82%, p = 0.02), and TBI was associated with a 1.76 reduction in FMD adjusting for age (F(2,33) = 3.86, p = 0.03). There was no significant difference in FMD between mild TBI versus moderate/severe TBI (5.66% vs 6.16%, p = 0.65). Conclusions: This study showed a reduction in FMD in children with acute TBI, highlighting the endovascular changes that occur with acute TBI at the blood-brain barrier. Further studies to evaluate the use of ultrasound-derived FMD measurement to predict outcomes may serve as a valuable tool to guide therapeutic decisions.
Chong et al. (Sun,) studied this question.