Autoregulation Monitoring (VRx & VOx)
Why Autoregulation Matters
The optimal blood pressure differs between patients.
A blood pressure that is adequate for one patient may result in insufficient perfusion or excessive pressure for another.
Autoregulation monitoring enables clinicians to identify patient-specific blood pressure targets by evaluating how the brain responds to changes in blood pressure.
What is VRx?
Volume Reactivity Index (VRx) is a real-time measurement of the relationship between blood pressure (MAP) and cerebral blood volume (BVI).
VRx continuously evaluates whether cerebral blood vessels are responding appropriately to changes in blood pressure.
Clinical Interpretation
VRx < -0.3
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Intact autoregulation
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Stable cerebral blood flow
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Safe blood pressure range
VRx > 0.3
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Impaired autoregulation
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Pressure-dependent blood flow
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Increased risk of cerebral and organ injury
What is VOx?
Volume Oxygenation Index (VOx) evaluates the relationship between cerebral blood volume and cerebral oxygenation.
VOx provides insight into whether blood flow remains appropriately matched to metabolic demand.
Clinical Interpretation
VOx values near 0.0 suggest that cerebral blood flow and oxygen delivery remain appropriately matched to metabolic demand, consistent with stable cerebral perfusion and effective autoregulatory control.
Clinical Applications
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Cardiac Surgery: Identify patient-specific MAP targets during bypass and recovery.
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Neurocritical Care: Optimize cerebral perfusion following neurological injury.
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Critical Care: Support individualized blood pressure management in unstable patients.
Role in Personalized Blood Pressure Management
VRx helps identify the optimal blood pressure range.
VOx confirms that oxygen delivery remains stable within that range.
Together, these indices provide a comprehensive assessment of autoregulation and support individualized blood pressure management based on real-time cerebral physiology.