Sympathetic tone modulates portal venous pressure in alcoholic cirrhosis.

Sixteen alcoholic cirrhotic patients with portal hypertension were studied before and after 2.5 micrograms/kg intravenous clonidine. In six patients portal venous pressure was assessed simultaneously by wedged hepatic vein and transhepatic portal vein cannulation. Wedged hepatic vein pressure accurately reflected portal venous pressure both before and after clonidine (r = 0.912 and 0.940; p less than 0.01). In all the other ten patients, sympathetic tone, measured by total plasma noradrenaline spillover, was high (755 +/- 123 ng/min; normal 296 +/- 29 ng/min). It fell significantly after clonidine (378 +/- 95 ng/min; p less than 0.01). This fall was associated with a decrease in corrected wedged hepatic vein pressure (18.6 +/- 1.1 to 13.4 +/- 0.5 mm Hg; p less than 0.01) but no change in estimated hepatic blood flow (934 +/- 94 to 976 +/- 102 ml/min), indicating a fall in postsinusoidal hepatic vascular outflow resistance. Clonidine-induced changes in mean arterial pressure and cardiac output were independent of the change in portal venous pressure. The results suggest that in alcoholic cirrhosis there is a labile component of hepatic vascular resistance which is partly under sympathetic nervous control and is thus potentially sensitive to pharmacological control.