Autoregulation of cerebral blood flow

Gebremedhin D, Lange AR, Lowry TF, Taheri MR, Birks EK, et al. 2000. Production of 20-HETE and its role in autoregulation of cerebral blood flow. Circ Res 87 60-65. 

Dirnagl U, Pulsinelli W (1990) Autoregulation of cerebral blood flow in experimental focal brain ischemia. J Cereb Blood Flow Metab 10 327-336... 

Nervous System Halothane dilates the cerebral vasculature, increasing cerebral blood flow under most conditions. This increase in blood flow can increase intracranial pressure in patients with space-occupying intracranial masses, brain edema, or preexisting intracranial hypertension. Thus, halothane is relatively contraindicated in patients at risk for elevated intracranial pressure. Halothane also attenuates autoregulation of cerebral blood flow. 

Harper, A.M., Autoregulation of cerebral blood flow influence of the arterial blood pressure on the blood flow through the cerebral cortex. J Neurol Neurosurg Psychiatry, 1966. 29(5) p. 398-403. 

Jalan R., Olde Damink S. W., Deutz N. E., Hayes P. C., and Lee A. (2001) Restoration of cerebral blood flow autoregulation and reactivity to carbon dioxide in acute liver failure by moderate hypothermia. Hepatology 34,50-54. 

Traon AP, Costes-Salon MC, Galinier M et al. (2002). Dynamics of cerebral blood flow autoregulation in hypertensive patients. Journal of Neurology Science 195 139-144 van der Grond J, Eikelboom BC, Mali WPThM (1996). Flow-related anaerobic metabolic changes in patients with severe stenosis of the internal carotid artery. Stroke 27 2026-2032... 

Bodo, M., Pearce, F.J., Baranyi, L., Armonda, R.A., 2005a. Changes in the intracranial rheoencephalogram at lower limit of cerebral blood flow autoregulation. Physiol. Meas. 26, SI—S17. 

Captopril is the fastest of the oral ACE inhibitors. It can also be used sublingually in patients who cannot swallow. Captopril shifts the entire curve of cerebral autoregulation in such a way that cerebral blood flow is maintained as the systemic pressure falls. Caution is needed in patients with significant renal... 

Sevoflurane has a dose-dependent effect on cerebral blood flow and intracranial pressure cerebral autoregulation is preserved (this is not the case with isoflurane). During hypocarbia, in the absence of nitrous oxide, 1 MAC does not increase intracranial pressure (ICP). It reduces the cerebral metabolic rate for oxygen (CMR02) by approximately 50% at concentrations approaching 2 MAC. This is similar to the reduction observed during isoflurane anaesthesia. 

Flow to the brain tissue is precisely regulated by a process of autoregulation, according to local chemical conditions. Cerebral blood vessels dilate and so increase blood flow in response to decreased pH and arterial PO2 and to increased arterial PCO2, conditions associated with increased metabolic activity. The neurones are very sensitive to changes in cerebral blood flow interruption of flow for a few seconds causes unconsciousness. 

The brain uses a substantial proportion of body oxygen and there is a generous blood supply to the brain from the carotid and vertebral arteries. Interruption of brain blood flow for more than a very short time causes neuronal damage and ultimately cell death. Cerebral blood flow is normally controlled by autoregulation. 

Cerebral blood flow depends on cerebral perfusion pressure and cerebrovascular resistance. The perfusion pressure is the difference between systemic arterial pressure at the base of the brain when in the recumbent position and the venous pressure at exit from the subarachnoid space, the latter being approximated by the intracranial pressure. Cerebral perfusion pressure divided by cerebral blood flow gives the cerebrovascular resistance. In normal humans, cerebral blood flow remains almost constant when the mean systemic blood pressure is between approximately 50 and 170mmHg, which, under normal circumstances when the intracranial venous pressure is negligible, is the same as the cerebral perfusion pressure. This homeostatic mechanism to maintain a constant cerebral blood flow in the face of changes in cerebral perfusion pressure is known as autoregulation (Reed and Devous 1985 Powers 1993). Autoregulation is less effective in the elderly, and so postural hypotension is more likely to be symptomatic (Wollner et al. 1979 Parry et al. 2006). 

Reed G, Devous M (1985). South-western Internal Medicine Conference cerebral blood flow autoregulation and hypertension. American Journal of Medical Science 289 37-44... 

It seems that the changes in the cerebral autoregulation associated with migraine can strongly modify the multifractality of middle cerebral artery blood flow. The constriction of the multifractal to monofractal behavior of the blood flow depends on the statistics of the fractional derivative index. As the distribution of this parameter narrows down to a delta function, the nonlocal... 

The cerebral autoregulation (CA) mechanism refers to the cerebral blood flow (CBF) tendency to maintain relatively constant in the brain despite changes in mean arterial blood pressure (MABP) in the interval from 50-170 mmHg [1]. Over the last decade, considerable advances have been developed in the safety and accessibility of non-invasive equipment. A technique using a transcraniai Doppler (TCD) was introduced to evaluate the dynamic response of CA in humans [2]. Rapid drops in arterial blood pressure (ABP) caused by the release of thigh blood pressure cuffs were... 

Waltz AG, Sundt TM Jr (1968) Influence of systemic blood pressure on blood flow and microcirculation of ischemic cerebral cortex a failure of autoregulation. Prog Brain Res 30 107-112... 

Hardy, P., Varma, D.R., Chemtob, S. (1997). Control of cerebral and ocrdar blood flow autoregulation in neonates. Pediatr. Clin. N. Am. 44 137-52. 

---