Vasoactive substances in the circulatory dysfunction of cirrhosis

Patients with cirrhosis and portal hypertension exhibit characteristic haemodynamic changes with a hyperkinetic systemic circulation, abnormal distribution of the blood volume, and neurohumoral dysregulation. Moreover, the circulating levels of several vasoactive substances may be elevated. Splanchnic vasodilatation is of pathogenic significance for the low systemic vascular resistance and abnormal volume distribution, which are important elements in the development of the concomitant cardiac dysfunction, recently termed cirrhotic cardiomyopathy. The systolic and diastolic functions are impaired with direct relation to the degree of liver dysfunction. Significant pathophysiological mechanisms seem to include a reduced beta-adrenergic receptor signal transduction, defective cardiac excitation-contraction coupling, and conductance abnormalities. Various vasodilators. such as nitric oxide and calcitonin gene-related peptide, are among candidates in the vasodilatation and the increased arterial compliance recently described in advanced cirrhosis. Reflex-induced enhanced sympatho-adrenal activity, activation of the renin-angiotensin-aldosterone system, and elevated circulating vasopressin and endothelin-1 are implicated in the haemodynamic counter-regulation in cirrhosis. Recent research has focused on the assertion that the haemodynamic and neurohumoral abnormalities in cirrhosis are part of a general cardiovascular dysfunction influencing the course of the disease, with reduction of organ function and sodium-water retention as the outcome. These aspects are relevant to therapy.