Plasma atrial natriuretic peptide and renin‐aldosterone in patients with cirrhosis and ascites: Basal levels, changes during daily activity and nocturnal diuresis

Measurements of plasma atrial natriuretic peptide concentrations at 8 AM showed raised levels in 21 patients with cirrhosis and ascites (10.5 ± 0.8 pmol/L) compared with levels in 10 age‐matched controls (4.1 ± 0.64 pmol/L; p < 0.0001). In eight patients and 10 controls, atrial natriuretic peptide, plasma renin activity, plasma aldosterone and urinary sodium excretion were measured every 4 hr for 24 hr. Subjects were mobile between 8 AM and 11 PM and supine from 11 PM to 8 AM. In controls, urinary sodium excretion was highest between 4PM and 11 PM (19.34 ± 3.74 μmol/min) and lowest between midnight and 8 AM (7.06 ± 1.23 μmol/min; p < 0.001). In patients, urinary sodium excretion was 0.63 ± 0.14 μmol/min between 4 PM and midnight and 1.85 ± 0.71 μmol/min (p < 0.08) between midnight and 8 AM. In patients during the day, mean plasma atrial natriuretic peptide concentration did not change despite large individual variation, but large, sustained rises in plasma renin activity and plasma aldosterone were seen. Correlations were noted between atrial natriuretic peptide and urinary sodium excretion between midnight and 8 AM (r = 0.65; p < 0.02) and 4 PM and midnight (r = 0.54; p < 0.05) but not between 8 AM and 4 PM. Plasma renin activity dropped from 12.54 ± 2.49 at midnight to 7.41 ± 0.88 pmol/hr/ml at 8 AM (p < 0.05); plasma aldosterone decreased from 1,032 ± 101 to 798 ± 56 pmol/L (p < 0.05). These findings are consistent with the hypothesis that atrial natriuretic peptide contributes to the nocturnal natriuresis of cirrhosis; it is possible that reduction in the activity of the renin‐aldosterone system in recumbency may allow the natriuretic effect of this substance to become manifest. (HEPATOLOGY 1992;16:82–88.)