Background: Patient-specific epidemiologic ICP thresholds in adult TBI have emerged, using the relationship between pressure reactivity index (PRx) and ICP, displaying stronger association with outcome over existing guideline thresholds. The goal of this study was to explore this relationship in a multi-center cohort in order to confirm the previous finding.

Methods: Using the Collaborative European Neuro Trauma Effectiveness Research in TBI (CENTER-TBI) high-resolution intensive care unit (ICU) cohort, we derived individualized epidemiologic ICP thresholds for each patient using the relationship between PRx and ICP. Mean hourly dose of ICP was calculated for every patient for the following thresholds: 20 mm Hg, 22 mm Hg and the patient’s individual ICP threshold. Univariate logistic regression models were created comparing mean hourly dose of ICP above thresholds to dichotomized outcome at 6 to 12-months, based on Glasgow Outcome Score – Extended (GOSE) (alive/dead - GOSE >=2/GOSE=1; favourable/unfavourable – GOSE 5 to 8/GOSE 1 to 4, respectively).

Results: Individual threshold were identified in 65.3% of patients (n=128), in keeping with previous results (23.0 +/- 11.8 mm Hg (IQR: 14.9 to 29.8 mm Hg)). Mean hourly dose of ICP above individual threshold provides superior discrimination (AUC 0.678, p=0.029), over mean hourly dose above 20 mm Hg (AUC = 0.509, p=0.03) or above 22 mm Hg (AUC = 0.492, p=0.035) on univariate analysis for alive/dead outcome at 6 to 12 months. The AUC for mean hourly dose above individual threshold trends to higher values for favourable/unfavourable outcome, but fails to reach significance (AUC = 0.610, p=0.060). This was maintained when controlling for baseline admission characteristics.

Conclusions: Mean hourly dose of ICP above individual epidemiologic ICP threshold has stronger associations with mortality compared to the dose above BTF defined thresholds of 20 or 22 mm Hg, confirming prior findings. Further studies on patient specific epidemiologic ICP thresholds are required.