The hyperdynamic circulation in cirrhosis: an overview

The hyperdynamic circulation begins in the portal venous bed as a consequen ce of portal hypertension due to the increased resistance to flow from alte red hepatic vascular morphology of chronic liver disease. Dilatation of the portal vein is associated with increased blood flow, as well as the openin g up or formation of veno-venous shunts and splenomegaly. At the same time, portal hypertension leads to subclinical sodium retention resulting in exp ansion of all body fluid compartments, including the systemic and central b lood volumes. This blood volume expansion is associated with vasorelaxation , as manifested by suppression of the renin-angiotensin-aldosterone system, initially only when the patient is in the supine position. Acute volume de pletion in such patients results in normalisation of the hyperdynamic circu lation, whilst acute volume expansion results in exaggerated natriuresis. A s liver disease progresses and liver function deteriorates, the systemic hy perdynamic circulation becomes more manifest with activation of the renin-a ngiotensin-aldosterone system. The presence of vasodilatation in the presen ce of highly elevated levels of circulating vasoconstrictors may be explain ed by vascular hyporesponsiveness due to increased levels of vasodilators s uch as nitric oxide, as well as the development of an autonomic neuropathy. However, vasodilatation is not generalised, but confined to certain vascul ar beds, such as the splanchnic and pulmonary beds. Even here, the status m ay change with the natural history of the disease, since even portal blood flow may decrease and become reversed with advanced disease. The failure of these changes to reverse following liver transplantation may be due to rem odelling and angiogenesis. (C) 2001 Elsevier Science Inc. All rights reserv ed.