Clinical

Higher ammonia levels linked to worse outcome in acute liver failure

Last Updated: 2006-01-12 16:15:50 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Higher levels of arterial ammonia predict worse outcomes in patients with acute liver failure, a new study from India shows. Based on the findings, ammonia-lowering therapies should be investigated in these patients, Dr. S. K. Acharya of All India of Medical Sciences in New Delhi and colleagues conclude.

While ammonia neurotoxicity is known to occur in liver failure patients, it has not been clear how levels of ammonia relate to severity of cerebral dysfunction or to patient outcome, Dr. Acharya and his team note in the January issue of Gut.

To investigate, the researchers followed 80 patients with acute liver failure, 52.5% of whom died. Eighty percent of cases were due to viral hepatitis.

Median ammonia levels were 174.7 micromoles per liter in patients who died, compared to 105.0 for those who survived, the researchers found. Higher ammonia levels conferred a significantly greater risk of deeper encephalopathy, cerebral edema, need for ventilation and seizures.

A cutoff of 124 micromoles per liter was 78.6% sensitive and 76.3% specific for predicting mortality, Dr. Acharya and colleagues report, while it had 77.5% diagnostic accuracy.

Logistic regression analysis found arterial pH, cerebral edema and ammonia levels were independently associated with mortality, with a 10.9-fold greater risk of death seen with higher ammonia levels. Mortality odds ratios were 6.6 with pH below 7.40 and 12.6 with cerebral edema.

"Our findings encourage viewing acute liver failure as a 'hyperammonaemic state,' and provide a rational background for the use of ammonia lowering therapies," the researchers conclude. Such therapies could include ornithine aspartate or sodium benzoate to boost peripheral utilization of ammonia, they note.

Gut 2006;55:98-104.