Hyperdynamic Circulation in portal Hypertension : Pathophysiology and Effects of Vasoactive Substances

点击翻译按钮获取中文摘要

1. Pathophysiology of Hyperdynamic Circulation in Cirrhosis and Portal Hypertension(1) Hemodynamic characteristics in various vascular bedsPeripheral arterial vasodilatation which plays an important role in the initiation of hyperdynamic circulation occurred mainly in the splanchnic circulation. Glucagon and atrial natriuretic peptide contributed to this phenomenon. Hyperdynamic splanchnic circulation developed as liver disease progresses. However, portal outflow pattern was different in patients with esophageal varices and patients with gastric varices. Renovascular constriction seen in patients with hepatorenal syndrome was responsible for kidney's homeostatic response to underfilling of the splanchnic arterial circulation. In liver circulation, hepatic arterial buffer response to altered portal blood flow was reduced.(2) Response to physiological stimuliSplanchnic hyperemia was observed after meal ingestion. Recumbent posture also caused similar change associated with increased atri … More al natriuretic peptide levels. Upright posture reduced esophageal variceal blood flow and blunted postprandial splanchnic hyperemia. Thus, meal ingestion and recumbent posture seemed to be risk factors for variceal bleeding. Furthermore, chronological examination showed that plasma atrial natriuretic peptide levels and cyclic guanosine monophosphate level which reflects activation of the guanylate cyclase receptors by the peptide peaked at night. This finding may explain why patients with cirrhosis tend to have esophageal variceal bleeding episodes at night.2. Hemodynamic Effect of Vasoactive Substances in Cirrhosis and Portal HypertensionVasopressin and propranolol decreased splanchnic inflow, resulting in reduction in collateral blood flow. Individual variability of portal pressure response to propranolol was thought to be heterogeneity of the beta-2 adrenoceptor status. Smoking decreased splanchnic blood flow, resulting in reduction in portal blood flow, suggesting that nicotine has potential portal pressure reducing effect. Less