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Cerebral autoregulation monitoring in acute traumatic brain injury: what’s the evidence?

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Calviello, LA 
Zeiler, FA 


Cerebral autoregulation is conceptualized as a vascular self-regulatory mechanism within the brain. Controlled by elusive relationships between various biophysical processes, it functions to protect the brain against potential damages caused by sudden changes in cerebral perfusion pressures and flow. Following events such as traumatic brain injuries (TBI), autoregulation may be compromised, potentially leading to an unfavorable outcome. In spite of its complexity, autoregulation has been able to be quantified non-invasively within the neuro-critical care setting with the aid of transcranial Doppler. This information is interpreted particularly through calculated derived indices based on commonly-monitored input signals such as arterial blood pressure and intracranial pressure (i.e. Pressure reactivity index (PRx), mean flow index (Mx), etc.). For example, PRx values that trend towards positive numbers are correlated with unfavorable outcome. These predictors are primarily surrogate markers of cerebral hemodynamic activity, although suggesting robust correlations between these indices and patient outcome. This review of the literature seeks to explain the methodology behind the calculations of various measures of autoregulation in adult patients suffering from traumatic brain injuries, and how they can interact with one another to both create larger effects on patient outcome and general outcome prediction models. Insight into the driving forces behind cerebral autoregulation is imperative for guiding both clinical decision-making and global treatment protocols for neuro-critically ill patients. The evidence that autoregulation-oriented therapy may improve outcome after TBI is still oscillating around Level III.



brain injuries, traumatic, intracranial pressure, cerebrovascular circulation, ultrasonography, doppler, transcranial, spectroscopy, near-infrared

Journal Title

Minerva Anestesiologica

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Edizioni Minerva Medica
Medical Research Council (G0600986)
Medical Research Council (G0600986/1)
Joseph Donnelly is supported by the Woolf Fisher Trust (New Zealand). The funder had no influence over the contents of this manuscript. Frederick A. Zeiler has obtained financial support from: The Royal College of Surgerons of Canada, Harry S. Morton Traveling Fellowship in Surgery, University of Manitoba - McLaughlin Fellowship in Medicine, University of Manitoba - Dean’s Fellowship, the Manitoba Medical Services Foundation (MMSF) and the University of Manitoba Clinican Investigator Program. Eric P. Thelin has obtained financial support from the Swedish Society of Medicine. The funder had no influence over the contents of this manuscript. Both Peter Smielewski and Marek Czosnyka receive licensing fees from ICM+ software (Cambridge Enterprises, Ltd.).