Abstract
BackgroundSeveral methods have been proposed to measure cerebrovascular autoregulation (CA) in traumatic brain injury (TBI), but the lack of a gold standard and the absence of prospective clinical data on risks, impact on care and outcomes of implementation of CA-guided management lead to uncertainty.AimTo formulate statements using a Delphi consensus approach employing a group of expert clinicians, that reflect current knowledge of CA, aspects that can be implemented in TBI management and CA research priorities.MethodsA group of 25 international academic experts with clinical expertise in the management of adult severe TBI patients participated in this consensus process. Seventy-seven statements and multiple-choice questions were submitted to the group in two online surveys, followed by a face-to-face meeting and a third online survey. Participants received feedback on average scores and the rationale for resubmission or rephrasing of statements. Consensus on a statement was defined as agreement of more than 75% of participants.ResultsConsensus amongst participants was achieved on the importance of CA status in adult severe TBI pathophysiology, the dynamic non-binary nature of CA impairment, its association with outcome and the inadvisability of employing universal and absolute cerebral perfusion pressure targets. Consensus could not be reached on the accuracy, reliability and validation of any current CA assessment method. There was also no consensus on how to implement CA information in clinical management protocols, reflecting insufficient clinical evidence.ConclusionThe Delphi process resulted in 25 consensus statements addressing the pathophysiology of impaired CA, and its impact on cerebral perfusion pressure targets and outcome. A research agenda was proposed emphasizing the need for better validated CA assessment methods as well as the focused investigation of the application of CA-guided management in clinical care using prospective safety, feasibility and efficacy studies.
Highlights
In the past decades, identifying preventable and manageable causes of secondary brain injury has led to reduced morbidity and mortality from severe traumatic brain injury (TBI)
The panel was composed based on the following criteria: (1) current and active bedside clinical expertise as a physician in the acute care for adult severe TBI patients, (2) active research and/or recent publications in this field and academic appointment, (3) sufficient representation of the involved disciplines of neurosurgery, neurocritical care and neuroanesthesiology, (4) willingness, availability and ability to commit to the Delphi study on cerebrovascular autoregulation (CA)
The following methods to measure CA were subjected to review by the experts: Autoregulation Index (ARI) [28]; Transfer function analysis methods based on transcranial Doppler (TCD) flow velocity [29]; ICP response to arterial blood pressure (ABP) manipulation [3, 4]; PRx [17]; L-PRx [30]; LAx [31]; Mx [16]; ORx [32]; Lx [33]; TOx [34]; THx [34]; correlation of extracellular glutamate measured with microdialysis and cerebral perfusion pressure (CPP) [35]; and CBFx [36]
Summary
In the past decades, identifying preventable and manageable causes of secondary brain injury has led to reduced morbidity and mortality from severe traumatic brain injury (TBI). Several methods to assess CA have been proposed and tested in clinical research, but a consensus on their accuracy, reliability and clinical utility is still lacking These methods are based on the effect of induced alterations or spontaneous fluctuations of arterial blood pressure (ABP) on surrogate measures for CBF (e.g., intracranial pressure (ICP), the pressure–volume index; transcranial Doppler (TCD) flow velocities) or on direct CBF measurements (e.g., cortical laser Doppler flow (LDF) or perfusion imaging). Results: Consensus amongst participants was achieved on the importance of CA status in adult severe TBI pathophysiology, the dynamic non-binary nature of CA impairment, its association with outcome and the inadvisability of employing universal and absolute cerebral perfusion pressure targets.
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