Abstract

Background and aims: In patients with cirrhosis, hepatic encephalopathy is often precipitated by dehydration. This study tests the hypothesis that volume expansion in cirrhotic patients increases renal ammonia excretion.

Patients and methods: Sixteen well compensated cirrhotic patients (mean Pugh score 6.7 (SEM 0.4)) were studied after an overnight fast. One litre of 0.9% saline was administered to patients intravenously over one hour. Plasma and urinary ammonia and sodium, renal plasma flow (RPF), glomerular filtration rate (GFR), plasma renin activity (PRA), and angiotensin II (ANG II) were measured before, during, and two hours after saline infusion.

Results: Saline infusion resulted in a significant reduction in plasma ammonia (93 (SEM 7) to 56 (4) μmol/l; p<0.05) and RPF and GFR increased (p<0.05). Urinary ammonia excretion increased (p<0.05) significantly. There was a significant reduction in ANG II and PRA (p<0.05 for each) and the change in ammonia excretion correlated directly with the change in urinary sodium excretion (p<0.007), ANG II (p<0.002), and PRA (p<0.01). The mean increase in urinary ammonia excretion during the observation period was 1.08 mmol. Assuming a volume of distribution of 45 litres, the corresponding change in whole body ammonia during the same period was 1.67 mmol.

Conclusion: The results of this study suggest that volume expansion reduces plasma ammonia concentration by increasing ammonia excretion and reducing ammoniagenesis.