The intracranial pressure curve correlates to the pulsatile component of cerebral blood flow

Abstract

Current methods to measure cerebral blood flow (CBF) in the neuro critical care setting cannot monitor the CBF continuously. In contrast, continuous measurement of intracranial pressure (ICP) is readily accomplished, and there is a component of ICP that correlates with arterial inflow of blood into the cranial cavity. This property may have utility in using continuous ICP curve analysis to continuously estimate CBF. We examined the data from 13 patients, monitored with an intraventricular ICP device determining the pulsatile amplitude ICP_amp as well as the area under the ICP curve (AUC_ICP). Using an elastance measurement, the ICP curve was converted to craniospinal volume (AUC_ΔV). The patients were examined with Phase Contrast Magnetic Resonance Imaging (MRI), measuring flow in the carotid and vertebral arteries. This made it possible to calculate CBF for one cardiac cycle (ccCBF_MRtot) and divide it into the pulsatile (ccCBF_MRpuls) and non-pulsatile (ccCBF_MRconst) flow. ICP derived data and MRI measurements were compared. Linear regression was used to establish wellness of fit and ANOVA was used to calculate the P value. No correlation was found between ICP_amp and the ccICP_MRpuls (P = 0.067). In contrast there was a correlation between the AUC_ICP and ccCBF_MRpuls (R² = 0.440 P = 0.013). The AUC_ΔV correlated more appropriately with the ccCBF_MRpuls. (R² = 0.688 P < 0.001). Our findings suggests that the pulsatile part of the intracranial pressure curve, especially when transformed into a volume curve, correlates to the pulsatile part of the CBF.

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