Low-resolution pressure reactivity index and its derived optimal cerebral perfusion pressure in adult traumatic brain injury: a CENTER-TBI study

Lennart Riemann,Alexander Younsi,Klaus Zweckberger,Peter Smielewski,Marek Czosnyka,Erta Beqiri,Andreas Unterberg,Nino Stocchetti,Oliver Sakowitz

doi:10.1186/s13054-020-02974-8

Abstract

BackgroundAfter traumatic brain injury (TBI), brain tissue can be further damaged when cerebral autoregulation is impaired. Managing cerebral perfusion pressure (CPP) according to computed “optimal CPP” values based on cerebrovascular reactivity indices might contribute to preventing such secondary injuries. In this study, we examined the discriminative value of a low-resolution long pressure reactivity index (LPRx) and its derived “optimal CPP” in comparison to the well-established high-resolution pressure reactivity index (PRx).MethodsUsing the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study dataset, the association of LPRx (correlation between 1-min averages of intracranial pressure and arterial blood pressure over a moving time frame of 20 min) and PRx (correlation between 10-s averages of intracranial pressure and arterial blood pressure over a moving time frame of 5 min) to outcome was assessed and compared using univariate and multivariate regression analysis. “Optimal CPP” values were calculated using a multi-window algorithm that was based on either LPRx or PRx, and their discriminative ability was compared.ResultsLPRx and PRx were both significant predictors of mortality in univariate and multivariate regression analysis, but PRx displayed a higher discriminative ability. Similarly, deviations of actual CPP from “optimal CPP” values calculated from each index were significantly associated with outcome in univariate and multivariate analysis. “Optimal CPP” based on PRx, however, trended towards more precise predictions.ConclusionsLPRx and its derived “optimal CPP” which are based on low-resolution data were significantly associated with outcome after TBI. However, they did not reach the discriminative ability of the high-resolution PRx and its derived “optimal CPP.” Nevertheless, LPRx might still be an interesting tool to assess cerebrovascular reactivity in centers without high-resolution signal monitoring.Trial registrationClinicalTrials.gov Identifier: NCT02210221. First submitted July 29, 2014. First posted August 6, 2014.

Highlights

After traumatic brain injury (TBI), brain tissue can be further damaged when cerebral autoregulation is impaired
Following severe traumatic brain injury (TBI), secondary injury cascades occur that affect cerebral blood flow (CBF). They may lead to ischemia when the cerebral perfusion pressure (CPP), the pressure gradient for cerebral blood flow defined as arterial blood pressure (ABP) minus intracranial pressure (ICP), is too low or to hyperemia and increased ICP when the CPP is too high [1,2,3]
The proposed weaker discriminative ability could be further supported by our data especially when ICP and CPP were added to the IMPACT variables in a multivariate model, where pressure reactivity index (PRx) but not long pressure reactivity index (LPRx) remained a significant predictor

Summary

Introduction

After traumatic brain injury (TBI), brain tissue can be further damaged when cerebral autoregulation is impaired. Following severe traumatic brain injury (TBI), secondary injury cascades occur that affect cerebral blood flow (CBF) They may lead to ischemia when the cerebral perfusion pressure (CPP), the pressure gradient for cerebral blood flow defined as arterial blood pressure (ABP) minus intracranial pressure (ICP), is too low or to hyperemia and increased ICP when the CPP is too high [1,2,3]. Likely due to the heterogeneity of cerebral injuries in patients with TBI, a CPP-oriented therapy with one fixed target for all patients failed to demonstrate improved neurological outcome compared to ICPtargeted therapy in a large randomized-controlled trial [7] This is why a patient-customized approach has been proposed which uses the pressure reactivity index (PRx) to determine the optimal CPP (CPPopt) in an individual patient. The automated CPPopt algorithm introduced by Aries et al which uses a single, 4-h moving monitoring window to calculate CPPopt has been developed further to a multi-window algorithm

Methods

Results

Discussion

Conclusion