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

Minerva anestesiologica
Leanne A CalvielloMarek Czosnyka

Abstract

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, 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 ad...Continue Reading

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