P: 46 Ammonia Is an Independent Biomarker of Poor Outcomes in Patients With Advanced Cirrhosis on the Transplant Waiting List

Abstract

BACKGROUND: Ammonia plays a pivotal role in the development of hepatic encephalopathy (HE) and brain oedema in acute liver failure and is a poor prognostic biomarker. However, its utility as a prognostic biomarker in patients with cirrhosis remains unclear as there is no direct correlation with hyperammonemia and the manifestation of HE per se. It has recently been demonstrated that blood ammonia levels correlate with organ failure and are an independent risk factor for mortality in patients with cirrhosis and acute decompensation. The aim of this study was to determine whether ammonia levels in patients with advanced cirrhosis awaiting liver transplantation influence waiting list outcomes. METHODS: A retrospective observational study of 300 sequential cirrhotic adult patients listed for liver transplantation between January 2015 and December 2018 was undertaken. All patients had an arterial ammonia measured at the time of assessment for transplant. All patients were closely followed up until death or transplantation. The main outcomes were hospital admissions (and number of organ failures), infection and mortality. Chronic Liver Failure-Sequential Organ Failure Assessment criteria were used to determine the presence of organ failures. For the transplanted patients, post-op complications were recorded. RESULTS: 200 (66.7%) were male with mean age of 54.29 ± 10.4. Mean follow-up time was 722.6 days. 266 (88.7%) patients were transplanted, 15 (5.0%) were de-listed for being too sick for transplant or following clinical improvement, 14 (4.7%) died on the list and 5 (1.6%) were still active on list. 97 (32.3%) patients were hospitalized on the waiting list and 60 (20%) had evidence of at least one infection. On multivariate analysis, ammonia correlated with hospitalisation (P < 0.001), infection (P < 0.001) and all-cause mortality (P = 0.00135). Of the patients that had at least one hospital admission, ammonia was an independent predictor of the presence of acute-on-chronic liver failure (ACLF) (P = 0.01811). For the transplanted patients, ammonia levels correlated with the presence of post-op complications (P < 0.001). CONCLUSIONS: In this retrospective study, arterial ammonia at the time of listing for liver transplantation was an independent predictor of hospitalisation, ACLF, infection and mortality. These data suggest that blood ammonia may be an important determinant of wait-list survival and further prospective studies are warranted.