Association of blood pressure variability with clinical and biomarker outcomes in moderate to severe TBI: A TRACK-TBI study.

INTRODUCTION

Traumatic brain injury (TBI) represents a significant global health burden and often results in functional impairment. Blood pressure variability (BPV), a surrogate marker of autonomic dysfunction, has been shown to influence outcomes in patients with cerebrovascular disease. Increased BPV has been strongly linked to deviation from optimal cerebral perfusion pressure, which may elevate the risk of secondary brain injury and poor outcomes after TBI. This study aimed to investigate the association of early BPV with clinical and functional outcomes, as well as brain injury biomarkers, in patients with TBI.

METHOD: We conducted a retrospective cohort study using data from the Transforming Clinical Research and Knowledge in Traumatic Brain Injury Study (TRACK-TBI), which prospectively enrolled acute TBI patients across 18 United States Level 1 trauma centers between 2014-2018. The study population included adults with moderate-to-severe TBI who required intracranial pressure monitoring. The primary exposure was early BPV, calculated from hourly blood pressure measurements during the first 24 h after ICU admission; 72-hour BPV was examined in sensitivity analyses. Two BPV metrics were evaluated: systolic standard deviation (SSD) and average real variability (ARV). The primary outcome was the 6-month Glasgow Outcome Scale-Extended score specific to TBI (GOSE-TBI). Secondary outcomes included in-hospital mortality, GOSE-TBI at 3 and 12 months, Disability Rating Scale (DRS) at 3 months, 6 months, and 12 months, and blood-based brain injury biomarkers [glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), neuron-specific enolase (NSE), S100 calcium-binding protein B (S100B), and the inflammatory biomarker C-reactive protein (CRP)]. Multivariable regression models were used to assess associations between BPV, clinical outcomes, and biomarker levels.

RESULTS

A total of 108 patients were included. The mean age (SD) was 41.3 years (17.3), 81% were male, and 81% identified as White. There were no statistically significant associations between 24-hour BPV and 6-month GOSE for either ARV (OR 0.84, 95% CI 0.68-1.05; p = 0.133) or SSD (OR 0.86, 95% CI 0.69-1.08; p = 0.194). Among secondary outcomes, higher 24-hour SSD was associated with increased odds of in-hospital mortality (OR 1.13, 95% CI 1.00-1.27; p = 0.048). Higher average 72-hour SSD was also associated with higher hs-CRP levels (Ratio 1.04, 95% CI 1.00-1.07; p = 0.036).

CONCLUSION

Early BPV was not associated with GOSE-TBI at 6 months or most blood-based brain injury biomarkers. However, higher 24-hour SSD may be associated with increased in-hospital mortality. The prognostic value of BPV warrants confirmation in future prospective studies.