Ammonia clearance with haemofiltration in adults with liver disease

Background & AimsAmmonia is recognized as a toxin central to complications of liver failure. Hyperammonaemia has important clinical consequences, but optimal means to reduce circulating levels are uncertain. In patients with liver disease, continuous renal replacement therapy (CRRT) with haemofiltration (HF) is often required to treat concurrent kidney injury, but its effects upon ammonia levels are poorly characterized. To evaluate the effect of HF at different treatment intensities on ammonia clearance (AC) and arterial ammonia concentration. MethodsProspective study of adult patients with liver failure and arterial ammonia >100mol/L requiring CRRT using veno-venous HF. Arterial ammonia concentration and AC measured at 1 and 24h after initiation of low (35ml/kg/h) or high (90ml/kg/h) filtration volume. ResultsTwenty-four patients (10 acute liver failure, 10 chronic liver disease and 4 following liver resection) were studied. Clearance of urea and ammonia solutes correlated closely (r=0.819, P=0.007). Ammonia clearance correlated closely with ultrafiltration rate (r=0.86, P<0.001). At 1h, AC was 39 (34-54) ml/min (low volume) vs 85 (62-105) ml/min (high volume) CRRT, (P<0.001) and at 24h 44 (34-63) vs 105 (82-109) ml/min, (P=0.01). Overall, a 22% reduction in median arterial ammonia concentration was observed over 24h of HF from 156 (137-176) to 122 (85-133) mol/L, (P0.0001). ConclusionClinically significant ammonia clearance can be achieved in adult patients with hyperammonaemia utilizing continuous VVHF. Ammonia clearance is closely correlated with ultrafiltration rate. HF was associated with a fall in arterial ammonia concentration.