Pressure reactivity index

rdf:langString Pressure reactivity index

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rdf:langString Pressure reactivity index or PRx is tool for monitoring cerebral autoregulation in the intensive care setting for patients with severe traumatic brain injury or subarachnoid haemorrhage, in order to guide therapy to protect the brain from dangerously high or low cerebral blood flow. PRx uses mathematical algorithms to calculate the correlation between arterial blood pressure and intracranial pressure. PRx assesses for correlations at low frequencies, below 0.5 Hz, and thus ignores individual pulses while capturing the effects of respiratory-driven variation in arterial pressure as well as other longer-acting stimuli. Under normal conditions, cerebral autoregulation ensures that cerebral blood flow is unchanged despite variations in blood pressure by regulating the cerebral vessels. For example, if the blood pressure increases, the cerebral vessels vasoconstrict to keep cerebral blood flow normal, whereas a decrease in blood pressure would lead to vasodilation of the cerebral vessels to increase blood flow. The cerebrovascular reactions to changes in blood pressure generates a corresponding effect on the intracranial pressure. When the blood pressure increases and the vessels vasoconstrict, the cerebral blood volume is reduced. According to the Monro-Kellie doctrine, less cerebral blood volume leads to a reduction in the intracranial pressure. If the blood pressure instead would decrease, the cerebral vessels would vasodilatate, with a resulting increase in cerebral blood volume.

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