Increase In Cortical Blood Flow Research Articles

Effect of intracranial hypotension on cerebral blood flow.

Intracranial hypotension increases cerebral blood flow. In dogs the average increase in cortical blood flow was 30 ml./100 g/min (47%) when the intracranial pressure was lowered acutely from 100 to 40 mm CSF. Permanent intracranial hypotension was established in seven demented patients using a ventriculoatrial shunt. The mean post shunt pressure was 50 mm CSF. In this group, the cerebral vascular resistance decreased 32%, the cortical blood flow increased 37%, and the relative weight of functional grey matter increased 44%. The systemic blood pressure was 8% lower. The increase in cerebral blood flow is the result of an increase in the pressure differential between the precapillary arterioles and the veins. In addition, the vessels dilate in response to the decreased external pressure. This increase in cerebral blood flow may be the mechanism for improvement in patients with normal pressure hydrocephalus who are shunted.

Cerebral circulation. Effects of vasodilating drugs on blood flow and the microvasculature of ischemic and nonischemic cerebral cortex.

Vasoactive drugs were given intravenously to 14 cats that had unilateral occlusion of a middle cerebral artery. Measurements of cortical blood flow (CBF) and observations of the superficial cortical microvasculature were made bilaterally before and after the injection of each drug. Papaverine produced increases of CBF of the nonischemic hemispheres of seven of eight animals despite decreases of mean systemic arterial blood pressure (MABP). Hexobendine also produced decreases of MABP, but CBF increased in only two of six animals. Blood flow did not increase in any of the three animals given ergot alkaloids (Hydergine). None of the drugs consistently produced increases of CBF of the ischemic hemispheres. Decreases of CBF that occurred in the ischemic hemispheres were related to decreases of MABP and impairment of autoregulatory processes. Paradoxic responses to increases of arterial carbon dioxide tension occurred in three animals.

Intrarenal Blood Flow Distribution (IRBF) in the Puppy Using Xenon Washout and Microspheres

Total renal blood flow measured by the 133Xenon washout (Xe) rose from 1.5 ml/g/min at 6 wks. to 3.5 at 16 wks. of age in 30 canine puppies.IRBF analyzed from the Xe curve showed Component I (CI) increased from 1.7 ml/g/min at 6 wks. to 4.6 at 16 wks. and Component II (CII) increased from 0.9 at 6 wks. to 1.1 at 16 wks. The ratio CII/CI was 0.55 at 6 wks. and fell to 0.25 at 16 wks. (p<0.01). The low cortical flow was also demonstrated by 169Yb microsphere method. Anatomical vascular development using silicone rubber further showed in increase in cortical size with age. Cardiac output measured by indocyanine green in 8anesthetized puppies over an age range of 6-16 wks. remained at 90 ml/kg/min while RBF in ml/kg/min increased. The relatively low cortical flow at 6 wks. was associated with a PAH extraction ratio (EPAH) of 0.44 and filtration fraction (FF) of 0.40. EPAH increased to 0.75 at 12 wks. and FF decreased to 0.24 at 16 wks. These studies directly demonstrate for the first time underperfusion of the young puppy renal cortex as compared to the medulla. Renal functional maturation is accomplished in the canine by an increase in cortical blood flow during growth.