166 Admission Plasma GFAP but not UCH-L1 Correlates with Intracranial Hypertension in Severe Traumatic Brain Injury – A TRACK-TBI Study

INTRODUCTION: Plasma glial fibrillary acid protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) correlate with CT positivity and outcome in traumatic brain injury (TBI), but less is known about their role in acute management. Elevated intracranial pressure (ICP) is an important cause of secondary injury, but current methods to identify patients at risk are imprecise. METHODS: We conducted a retrospective analysis of the TRACK-TBI dataset. Patients = 17 years undergoing invasive ICP monitoring were included. Those with craniectomy prior to monitoring were excluded; patients were censored at the time of craniectomy, if performed. We tested for an association between plasma GFAP and UCH-L1 on day 1 and ICP and TIL over the first 5 hospital days using univariate statistics. A multivariate linear regression was performed to test the hypothesis that plasma biomarkers were independently associated with ICP burden after accounting for clinical and radiographic covariates. RESULTS: Of 229 subjects, 134 (59%) had at least one ICP reading over 22 mmHg in the first 24 hours. The mean proportion of ICP readings > 22 mmHg over 5 days was 14.7%. The mean maximum TIL was 3.4; 46 patients (20%) underwent craniectomy. Median day 1 GFAP and UCH-L1 concentrations were 4,972 and 985 pg/mL, respectively. Compared to those in the lowest quartile, patients in the highest quartile of GFAP concentrations had greater ICP burden (23.2% of readings > 22mmHg vs. 7.3%, P < 0.001) and maximum TIL (P = 0.002), and were more likely to undergo craniectomy (39% vs. 16%, P = 0.008). After adjusting for confounders, GFAP was independently associated with ICP burden (P = 0.002). There was no association between UCH-L1 and ICP or TIL. CONCLUSIONS: Plasma GFAP may help identify patients at risk for intracranial hypertension. Further research is required.