Significant Decrease In Flow Research Articles

Effect of Cardiac Arrest on Cerebral Circulation

The effect of 2 to 15 min of cardiac arrest on cerebral circulation was investigated in dogs and Rhesus monkeys. When circulatory arrest lasted longer than 5 minutes, angiographic changes of the no-reflow phenomenon were observed between 3 and 4 h after resuscitation in dogs but not in monkeys. These findings were (1) marked prolongation of the arterial phase in both intracranial and extracranial arteries; followed by (2) occasional evidence of dilatation of the proximal intracranial arteries with non-filling of the distal intracranial arteries; and (3) faint demonstration of the venous phase. Carbon black perfusion results were (1) diffuse lack of perfusion at the arteriolar-capillary level and (2) multifocal areas of filling defects. Regional cortical blood flow measurement in monkeys disclosed a significant decrease in flow starting from 3 h after re-establishment of circulation for those in which longer than 5 min of arrest was induced.

Endotoxin-induced regional circulatory changes in the unanesthetized monkey.

Endotoxin in eight unanesthetized monkeys produced a small decrease in cardiac output, a marked fall in blood pressure, and a decrease in total peripheral vascular resistance. The distribution of cardiac output was measured by injecting nuclide-labeled radioactive microspheres (50µ in diameter) into the left ventricle, and blood flow and vascular resistance were calculated for each organ. All vascular beds except that of the spleen reacted with variable degrees of vasodilation, and the most pronounced decreases in resistance were observed in the coronary, gastrointestinal, and adrenal vasculature. Cerebral flow was reduced, but flow was maintained in the brain stem and cerebellum. In contrast to studies in other species, both the gastrointestinal tract and the kidneys showed vasodilation and no significant decrease in flow during the early phase of endotoxemia. There is some similar evidence in humans of decreased total systemic peripheral resistance without abnormal myocardial function or pooling of blood during the early phase of endotoxemia. The acute regional circulatory changes we have found appear to indicate that endotoxin either directly or through secondary biochemical reactions initiates and maintains a generalized (except for the spleen) vasodilation that reflex compensatory mechanisms cannot overcome. This vasodilation is particularly critical in preventing maintenance of adequate blood flow to the cerebral hemispheres.

Effect of Vagotomy on Gastric Mucosal Blood Flow

Summary 1.The effect of vagotomy on gastric mucosal blood flow has been studied in 12 dogs using the method of clearance of krypton 85 . 2.Arterial PCO 2 and other parameters were maintained constant throughout the experimental period, and flows obtained bef ore vagotomy were compared with those after nerve section and sham operation. 3.Vagotomy produced a significant decrease in flow which was maintained for at least 2 hr in 10 of 12 dogs.