Cerebral Blood Flow in Cats After an Acute Hypertensive Insult With Damage to the Blood-Brain Barrier

Abstract

Xenon clearance method in anesthetized cats under controlled ventilation. An acute pressure increase in the carotid system increases the cerebrovascular permeability to Evans blue, indicating damage to the blood-brain barrier. In these conditions the reactivity of cerebral blood vessels toward changes in the acid-base balance is altered: the CO 2 reactivity is less pronounced, while the effect of increasing the plasma [HCO 3 ] is more pronounced than in normal cats. Autoregulatory capacity toward moderate alterations in arterial blood pressure or in intracranial pressure is well maintained in these conditions. Additional Key Wordshypertension pH autoregulation intracranial pressure D Evidence, summarized by Lassen, 1 suggests that the cerebrovascular response to CO 2 alterations is the result of extravascular pH changes occurring in brain tissue. In view of this hypothesis, the different diffusion characteristics of CO 2 and HCO 3 through the blood-brain barrier 2 could explain the contrast between the marked effects of acute respiratory changes and the inconsistent effects of acute metabolic changes in blood pH on cerebral blood flow (CBF).3 ' 4 Accordingly, a lesion of the blood-brain barrier could be expected to alter the reactivity of the cerebral vessels toward changes in the acid-base balance. This possibility was investigated in anesthetized cats in which the blood-brain barrier was acutely damaged by an abrupt hypertensive insult. MethodsThe experiments were carried out on adult cats. Under light thiopental anesthesia, the trachea was cannulated; polyethylene catheters were introduced in a femoral vein, femoral artery, and thyroid artery; the surface of the skull was widely exposed, and a needle was placed in the cisterna magna or in a lateral cerebral ventricle. After completion of the surgical preparation the animals were paralyzed with gallamine (Flaxedil®, 5 mg per kilogram per hour) and mechanically ventilated with a gas mixture containing 67.5% N 2 O, 25% O 2 , and 7.5% N 2 . Procaine (2%) was applied locally on the surface of the skin wounds.

Decreased cerebral blood flow after administration of sodium bicarbonate in the distressed newborn infant

“…The fact that p C 0~induced changes in cerebral extracellular pH readily influences the CBF in normal conditioas whereas changes in plasma bicarbonate at constant pCO2 do not, is probably related to the fact that CO, readily crosses the endothelid membrane whereas H and HCOacannot freely cross the intact blood-brain barrier. It has been demonstrated, however, that hypercapnia, o'r, in particular, damage to the blood-brain barrier induced by acute hypertension in cats, results in an increased reactivity of the cerebral blood flow to changes in the plasma bicarbonate concentration at constant pC0, (Pannier et al 1974, Pannier & Leusen 1975. The CBF was lowered to about half the normal value after intravenous infusion of about 18 ml 0.23 M Na2C03 per kg in cats with damage to the blood-brain barrier.…”

Fluorocarbon-23 measure of cat cerebral blood flow by nuclear magnetic resonance.

“…26 In the nine cats, CBF during inhalation of 60% FC-23 was not different from control CBF. The mean difference in CBF was -1.9 ml/100 g/min, and SD was 12.16.…”

Effect of non-respiratory alkalosis on brain tissue and cerebral blood flow in rats with damaged blood-brain barrier.

“…On the other hand, experiments on cats have shown that CBF can be affected by changes in plasma [HCO3] when the BBB is damaged. 2 The aim of the present experiments was to study the effect of changes in the plasma [HCOi] on brain tissue [HCOi] in the presence of a lesion of the BBB, and to relate CBF in these conditions to changes in the brain tissue. The experiments were performed on rats, to allow for tissue analysis.…”