Ammonia and partial pressure of ammonia — correlation with postural control, Child-Pugh-stage and reitan a test in patients with cirrhosis

Objective: The arterial concentration and the partial pressure of ammonia are elevated in patients with hepatic encephalopathy (HE). Postural instability is a possible symptom of HE. We investigated the relationship between the concentration/partial pressure of ammonia and postural control in patients with liver cirrhosis. Methods: 40 patients with cirrhosis of various etiologies (alcoholic: 21, viral: 14, other: 5) and Child-Pugh-Stages (A: 17, B: 11, C: 12) were tested for postural control using posturography, an objective method to quantify postural sway (Smart EquiTest, NeuroCom International) and compared to 15 healthy controls. Arterial ammonia concentrations and pH were measured and the partial pressure of ammonia calculated by standard methodology. Patients underwent neurological examination to exclude other causes for postural instability. Reitan A test was used to diagnose hepatic encephalopathy. Results: Patients with liver cirrhosis showed an impaired postural control compared to healthy controls. (Mann-Whitney U test: p = 0.001) The patients with encephalopathy (Reitan A > 60 sec) performed significantly worse in posturography than those without encephalopathy (Reitan A < 60 sec). (p = 0.004) In patients with impairment of postural control the concentrations (p = 0.03) and partial pressure (p = 0.01) of ammonia were significantly higher than in those without postural instability. The concentration/partial pressure of ammonia also correlated with the severity of liver disease (Child-Pugh-Stage: p = 0.02), (Child-Pugh-Score: Spearman R = 0.5; p = 0.0003) and performance on Reitan A test (Mann-Whitney U test: p = 0.005/0.006). Conclusion: The significant correlation of the arterial concentration/partial pressure of ammonia with postural control in patients with liver cirrhosis confirms that postural instability is part of the nenrologic alterations of hepatic encephalopathy.