Role of circulating neurotoxins in the pathogenesis of hepatic encephalopathy: potential for improvement following their removal by liver assist devices : Circulating toxins and hepatic encephalopathy

One hundred twenty-six patients with cirrhosis, hyperammonemia (>50 micromol/L), and chronic (persistent) hepatic encephalopathy (HE), which developed spontaneously without the existence of known precipitating factors, were enrolled in a randomized, double-blind, placebo-controlled clinical trial of intravenously administered L-ornithine-L-aspartate (OA). Patients with subclinical (grade 0, West-Haven criteria) hepatic encephalopathy (SHE), characterized by a prolonged number connection test A (NCT-A) time, and manifest HE (grades I and II, West-Haven criteria) were included in the investigation. The trial was planned as a confirmatory clinical trial OA administered in a dose of 20 g/d, as well as placebo, were dissolved in 250 mL of 5% fructose and infused intravenously for a period of 4 hours during 7 consecutive days with a superimposed protein load at the end of the daily treatment period. Primary variables were postprandial venous ammonia and NCT-A performance time measured following OA or placebo infusions to evaluate the net effect of the treatment on the prevention of the protein-induced hyperammonemia, and on parameters such as NCT-A influenced by hyperammonemia. Mental state gradation, portal systemic encephalopathy index (PSEI), and fasting ammonia levels were estimated as additional efficacy parameters. The data presented are based on the total study sample (intent-to-treat analysis), which included 63 patients in the placebo group and 63 patients in the OA group. Of the 126 patients, 114 met all the criteria for inclusion and completed the trial and treatment as outlined in the protocol (treated-per-protocol analysis). During baseline, the placebo and treatment groups were homogeneous with regard to mental states, NCT-A performance time, fasting venous blood ammonia levels, and Child-Pugh criteria. Although a slight improvement occurred in the placebo group, NCT-A performance times (P < .001) and postprandial venous ammonia concentrations in the OA-treated group showed improvements in comparison with placebo. In addition, venous fasting blood ammonia concentration (P < .01), mental state gradation (P < .001), and PSEI (P < .01), which includes the mental state gradation, NCT-A time, and postprandial venous ammonia in this trial, improved to a much higher degree in the OA group than in the placebo group. In subgroups retrospectively classified according to their initial mental state gradation, OA showed differential but uniformly significant efficacies in patients with manifest HE with respect to ammonia-lowering, improvement in NCT times, and mental state gradation. In patients with initial SHE, OA revealed differences between the medications in the psychometric test used. Adverse events consisting of mild gastrointestinal disturbances were observed in 3 of the OA-treated patients (5%). OA infusion appears to be a safe, effective treatment of chronic (persistent) manifest HE in cirrhotic patients. Additional investigations are required to assess the efficacy of OA in patients with SHE, as well as in patients with more severe grades of HE.

Cerebral ammonia metabolism was studied in five control subjects and five patients with severe liver disease exhibiting minimal hepatic encephalopathy. The arterial ammonia concentration in the control subjects was 30 +/- 7 mumol/L (mean +/- SD) and 55 +/- 13 mumol/L in the patients (p less than 0.01). In the normal subjects, the whole-brain values for cerebral blood flow, cerebral metabolic rate for ammonia, and the permeability-surface area product for ammonia were 0.58 +/- 0.12 ml g-1 min-1 0.35 +/- 0.15 mumol 100 g-1 min-1, and 0.13 +/- 0.03 ml g-1 min-1, respectively. In the patients, the respective values were 0.46 +/- 0.16 ml g-1 min-1 (not different from control), 0.91 +/- 0.36 mumol 100 g-1 min-1 (p less than 0.025), and 0.22 +/- 0.07 ml g-1 min-1 (p less than 0.05). The increased permeability-surface area product of the blood-brain barrier permits ammonia to diffuse across the blood-brain barrier into the brain more freely than normal. This may cause ammonia-induced encephalopathy even though arterial ammonia levels are normal or near normal and explain the emergence of toxin hypersensitivity as liver disease progresses. Greater emphasis on early detection of encephalopathy and aggressive treatment of minimal hyperammonemia may retard the development of ammonia-induced complications of severe liver disease.

Increasing evidence suggests that manganese deposition is responsible for the T1-weighted magnetic resonance imaging (MRI) signal hyperintensity consistently observed in pallidum of cirrhotic patients. However, the relationship between blood manganese and the etiology or severity of liver disease, as well as the neurological symptomatology in these patients, has not been well established. In the present study, blood manganese concentrations were measured by atomic absorption spectrometry together with MRI and neurological evaluation in 57 cirrhotic patients with various etiologies and severity of liver disease. Blood manganese concentrations were elevated in 67% of cirrhotic patients and were significantly higher in patients with previous portacaval anastomoses or transjugular intrahepatic portosystemic shunt (TIPS). Pallidal signal hyperintensity was observed in 88% of patients, and significant correlations were demonstrated between blood manganese and pallidal index (PI) (a measure of pallidal signal hyperintensity), as well as Child-Pugh score. Assessment of extrapyramidal symptoms using the Columbia rating scale revealed a significant incidence of tremor, rigidity, or akinesia in up to 89% of cirrhotic patients. However, there was no significant correlation between blood manganese and extrapyramidal symptoms, although severity of akinesia was significantly greater in Child-Pugh C patients. Extrapyramidal symptoms could result from a toxic effect of manganese on basal ganglia dopaminergic function. These findings further support a role for manganese in the etiology of pallidal MRI signal hyperintensity in patients with chronic liver disease.