Cerebral Blood Flow Autoregulation in Acute Intracranial Hypertension

Abstract

Summary: The present series of experiments was carried out to investigate CBP autoregulation during fixed levels of acute increased intracranial pressure (ICP). Three groups of six rats each, one with normal ICP (8 mm Hg), one with moderately increased ICP (30 mm Hg), and one with severely increased ICP (50 mm Hg), were investi gated. ICP was maintained by continuous infusion of lac tated Ringer solution into the cisterna magna. Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure -ICP, was increased by intravenously infused norepinephrine and decreased by controlled bleeding. In all groups the corresponding autoregulation curve included a plateau where CBP was independent of Abbreviations used: CPP, cerebral perfusion pressure; CVR, cerebrovascular resistance; ICP, intracranial pressure; JVP, jug ular venous pressure; LL, lower limit of autoregulation; MABP, mean arterial blood pressure. 519changes in CPP, demonstrating intact autoregulation. However, a significant shift of the lower limit of autoreg ulation (LL) toward lower CPP levels during severe in tracranial hypertension was observed (p < 0.006). In the controls the LL was found at CPP = 73 ± 6 mm Hg, in moderately increased ICP the LL was 59 ± 4 mm Hg, and in severely increased ICP the LL was 51 ± 4 mm Hg. These results indicate that an acute elevation of ICP ac tivates a reserve capacity of cerebral resistance vessels that dilate further below the normal physiological LL to maintain CBP at low levels of CPP.

Contribution of Cerebral Edema to the Neuronal Salvage Elicited by Stimulation of Cerebellar Fastigial Nucleus after Occlusion of the Middle Cerebral Artery in Rat

“…In two recent articles (Hauerberg and Juhler, 1994;Mutch, et aI., 1994), autoregulation is consid ered from the "classical" point of view-i.e., that there is an autoregulatory plateau, and if no plateau is present, the cerebral vasculature is acting abnor mally.…”

“…William I. Rosenblum raises some essential questions concerning the autoregulatory plateau with reference to our recent article (Hauerberg and Juhler, 1994). Cerebral autoregulation is classically described as a regulatory mechanism that maintains CBF constant within wide ranges of systemic arte-…”

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

“…Due to the highly effective control exerted by the mechanism of pressure-autoregulation, CBF is normally maintained within narrow limits for mean blood pressures (MBP) in the range 60-150 mm Hg (Paulson, Strandgaard & Edvinsson 1990). Not surprisingly, it is the CBF autoregulation mechanism itself that has been shown to be impaired in a number of conditions such as ischaemic stroke, severe head injury, carotid artery disease, intracranial hypertension, diabetes and liver failure (Aries et al 2010, Czosnyka et al 1996, Dawson et al 2000, Hauerberg, Juhler 1994, Kim et al 2008, Lagi et al 2002, Panerai 2008, White, Markus 1997, van Beek et al 2008.…”

Should we measure cerebral blood flow in head-injured patients?

“…the range of pressures where CBF is relatively stable despite variations in CPP is shifted towards higher values of CPP 97 and the range of CPP where CBF is stable can be smaller than in a normal brain. 98 Considering the association between outcome and autoregulation the question arises whether patients should be managed at a CPP consistent with the best vascular response, if possible on the autoregulatory plateau.This would require our ability to de ne this 'optimal' range of CPP in individual patients. In a retrospective study, 99 we have been able to identify such a range of CPP in twothirds of our head-injured patients using continuous monitoring of pressure reactivity.…”