Indeed, three of four studies showed an increase in cerebrovascular resistance assessed using TCD pulsatility ratio during lower body negative pressure, 5, 7, 8 and two studies showed a decrease during albumin or normal saline infusion. When the CBF was changed during acute central blood volume alteration, there must be a change in cerebrovascular resistance to account for the flow change because the blood pressure remained relatively stable. The finding that β 1-adrenergic blockade concurrently attenuated the increase in both CO and CBF induced by cycling corroborates this proposition. Therefore, the association between CO and CBF is a causal relationship. It was also unlikely to be ascribed to a change in cerebral metabolic activity, because these studies were done in resting and unanesthetized subjects. This association was unlikely to have been confounded by a change in either blood pressure or carbon dioxide because both parameters remained relatively stable except two studies in which carbon dioxide had a clinically significant drop after standing up 6 and lower body negative pressure, 7 respectively.
Each percentage change in CO corresponded to a 0.35% change in CBF, that is, there is about a 10% CBF decrease for a 30% CO reduction based on eight data pairs from five previous studies (R 2 = 0.9, fig. Outcome research relating to the management of CO and CBF in high-risk patients or during high-risk surgeries is needed.Ī distinct association between CO and CBF was demonstrated in young healthy volunteers whose central blood volume was decreased via lower body negative pressure 5, 7–9 or standing up 6 and increased via leg tensing, 6 albumin infusion, 8 or normal saline infusion 9 ( table 1). The clinical implications pertinent to the effect of CO on CBF are discussed. Given that CBF regulation is multifactorial but the various processes must exert their effects on the cerebral circulation simultaneously, the authors propose a conceptual framework that integrates the various CBF-regulating processes at the level of cerebral arteries/arterioles while still maintaining autoregulation. However, studies on the association between CO and CBF in patients with varying neurologic, medical, and surgical conditions were confounded by methodologic limitations. The overall evidence shows that an alteration in CO, either acutely or chronically, leads to a change in CBF that is independent of other CBF-regulating parameters including blood pressure and carbon dioxide. The authors reviewed the studies that investigated the association between CO and CBF in healthy volunteers and patients with chronic heart failure. The question of how a change in cardiac output (CO) affects CBF is fundamental, because CBF is dependent on constantly receiving a significant proportion of CO. SWFI is a minority-owned organization.Cerebral blood flow (CBF) is rigorously regulated by various powerful mechanisms to safeguard the match between cerebral metabolic demand and supply. SWFI facilitates sovereign fund, pension, endowment, superannuation fund and central bank events around the world. Sovereign Wealth Fund Institute (SWFI) is a global organization designed to study sovereign wealth funds, pensions, endowments, superannuation funds, family offices, central banks and other long-term institutional investors in the areas of investing, asset allocation, risk, governance, economics, policy, trade and other relevant issues.
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