Plasma noradrenaline in cirrhosis: a study of kinetics and temporal relationship to ascites formation.

The kinetics of plasma noradrenaline (NA) were studied in 14 patients with cirrhosis and ascites and 13 normal subjects. [3H]noradrenaline ([3H] NA) was infused intravenously to steady state and the spillover of NA into plasma and its clearance from plasma calculated. The increase in plasma NA in the cirrhotic patients was due to an increase in NA spillover (14.5 vs 3.9 nmol min-1m-2; P less than 0.001). NA plasma clearance was also increased in the cirrhotic patients (3.5 vs 2.11 min-1m-2; P less than 0.01). Plasma NA and dihydroxyphenylglycol (DHPG), a metabolite of NA of which a portion is formed after re-uptake of NA into sympathetic nerve endings, were then measured in 23 patients with cirrhosis and ascites, 17 patients with cirrhosis who had never had ascites, and 34 normal subjects. Both plasma NA and DHPG were significantly increased in the patients with ascites (NA 4.7, DHPG 14.7 nmol l-1 and in the patients with cirrhosis but no ascites (NA 3.8, DHPG 12.0 nmol l-1) compared with normal subjects (NA 1.9, DHPG 8.8 nmol 1-1). Therefore, the increase in plasma NA in cirrhosis is due to increased activity of the sympathetic nervous system rather than interference with the metabolism of NA or impaired neuronal uptake of NA. This increase appears to precede the development of ascites.