(842) Outcomes Following Prolonged Midazolam Administration After Pediatric Traumatic Brain Injury in Rats

Introduction: Following pediatric TBI, the most critically ill are often exposed to prolonged sedative administration. Benzodiazepines, which in preclinical studies can impair neurodevelopment and cognitive outcomes, are often used as an adjunctive class of sedatives. We hypothesized that early, prolonged exposure to midazolam following TBI would worsen outcomes in a pediatric preclinical model.

Methods: Male Sprague-Dawley rats (postnatal day, PND 17) were divided into four groups: naive (n=5), naive with sedation (n=9), TBI (n=12), and TBI with sedation (n=12). TBI groups underwent controlled cortical impact (CCI). Starting on post-injury day (PID) 1, sedation groups received 12 hours/day of sedation, using intraperitoneal injections of midazolam, given at intervals to maintain sedation based on a rating scale. Rats were divided into short term, mid-term, and long-term outcome groups (4, 28 and 60-100 after CCI). In long-term behavioral studies, the rats completed a visual discrimination touchscreen task, open-field and digital gait analysis and were then euthanized for ex-vivo brain MRI analysis.

Results: In short-term histologic studies, TBI-sedation rats had reduced neuroinflammation (Iba-1, CD68) in ipsilateral thalamus, and reduced cell death (TUNEL, caspase-8) in ipsilateral peritrauma cortex and dentate gyrus. In long-term behavioral testing, TBI-sedation rats committed more errors and required more correction trials on a touchscreen task of visual discrimination. TBI-sedation rats also spent less time in the center of the open field and had more deficits in stance, paw placement and posture on a digital gait analysis. Preliminary MRI demonstrated changes in white matter microstructure, including abnormalities in fractional anisotropy, structural coherence and directional diffusion in both TBI groups compared to naïve rats.

Conclusions: Short-term studies suggested potential neuroprotective properties of midazolam, but this did not translate into improvements in executive function or significant differences in white matter microstructure between the TBI and TBI-sedation groups.

Future studies will include additional MRI analyses and histologic analysis of long-term groups, and evaluation of synaptic integrity and density in the mid-term group of rats.