Exercise-induced hyperammonemia in patients with compensated chronic liver disease.

Plasma levels of ammonia and amino acids were measured during and after graded physical exercise in seven ambulatory patients with well-compensated chronic liver disease and in seven healthy controls. Plasma ammonia was similar in both groups at rest but reached significantly higher peak values (124.0 +/- 29.3 (SD) versus 74.7 +/- 17.7 mumol/l) in the patients with liver disease during exercise. The return to base line during the recovery period was delayed in the patients (T1/2 9.9 +/- 5.5 versus 2.3 +/- 1.0 min). Except for plasma taurine, which was significantly lower in the patients at rest and which showed a significant decrease in the controls but not in the patients during exercise, changes in the plasma concentration of amino acids were similar in the two groups. The increased exposure of patients with chronic liver disease to ammonia while performing an identical workload results from an impaired clearance of ammonia plus, possibly, an increased generation of ammonia in muscle working at a higher intensity. Since hyperammonemia may be associated with the sensation of fatigue, increases in plasma ammonia during daily physical activities might in part explain the easy fatigability often reported by patients with chronic liver disease.