• Teodor Svedung Wettervik, Erta Beqiri, Anders Hånell, Stefan Yu Bögli, Ihsane Olakorede, Xuhang Chen, Adel Helmy, Andrea Lavinio, Peter J Hutchinson, and Peter Smielewski.
• Department of Medical Sciences, Section of Neurosurgery, Uppsala University, 751 85, Uppsala, Sweden. teodor.svedung-wettervik@neuro.uu.se.
• Crit Care. 2025 Jan 12; 29 (1): 2020.

BackgroundThe oxygen reactivity index (ORx) reflects the correlation between focal brain tissue oxygen (pbtO2) and the cerebral perfusion pressure (CPP). Previous, small cohort studies were conflicting on whether ORx conveys cerebral autoregulatory information and if it is related to outcome in traumatic brain injury (TBI). Thus, we aimed to investigate these issues in a larger TBI cohort.Methods425 TBI patients with intracranial pressure (ICP)- and pbtO2-monitoring for at least 12 h, who had been treated at Addenbrooke's Hospital, Cambridge, UK, were included. Association between ORx and ICP, pressure reactivity index (PRx), CPP, ΔCPPopt (actual CPP-CPPopt [PRx based optimal CPP]), and pbtO2 were evaluated with generalized additive models (GAMs). Association between ORx and outcome (Glasgow Outcome Scale [GOS]) was investigated with logistic regressions and heatmaps for those 239 patients with GOS data.ResultsGAMs showed that ORx increased with higher ICP, PRx above + 0.30, CPP below 60-70 mmHg, and negative ΔCPPopt. In contrast to PRx, ORx did not increase at higher CPP. In outcome heatmaps, there was a transition towards unfavourable outcome when ORx exceeded + 0.50, particularly for longer durations, and in combination with high ICP, high PRx, low CPP, negative ΔCPPopt, and low pbtO2. In multivariable logistic regressions, higher ORx was associated with increased mortality.ConclusionsORx seemed to be sensitive to the lower, but not the upper, limit of autoregulation, in contrast to PRx which was sensitive to both. The combination of high values for both ORx and PRx was particularly associated with worse outcome and, thus, ORx may provide a complementary value to the global index PRx. ORx could also be useful to determine the safe and dangerous perfusion target intervals.© 2025. The Author(s).

29 keywords...

hide…