title: Ammonia clearance with haemofiltration in adults with liver disease.
abstract: OBJECTIVE
  Ammonia 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.
  
  
  METHODS
  Prospective study of adult patients with liver failure and arterial ammonia >100 μmol/L requiring CRRT using veno-venous HF. Arterial ammonia concentration and AC measured at 1 and 24 h after initiation of low (35 ml/kg/h) or high (90 ml/kg/h) filtration volume.
  
  
  RESULTS
  Twenty-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 1 h, AC was 39 (34-54) ml/min (low volume) vs 85 (62-105) ml/min (high volume) CRRT, (P < 0.001) and at 24 h 44 (34-63) vs 105 (82-109) ml/min, (P = 0.01). Overall, a 22% reduction in median arterial ammonia concentration was observed over 24 h of HF from 156 (137-176) to 122 (85-133) μmol/L, (P ≤ 0.0001).
  
  
  CONCLUSIONS
  Clinically 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.
authors.affiliation: Institute of Liver Studies, King's College Hospital Foundation Trust, London, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Slack
authors.forename: Georg
authors.initials: G
authors.lastname: Auzinger
authors.forename: Chris
authors.initials: C
authors.lastname: Willars
authors.forename: Tracy
authors.initials: T
authors.lastname: Dew
authors.forename: Rebecca
authors.initials: R
authors.lastname: Musto
authors.forename: Daniel
authors.initials: D
authors.lastname: Corsilli
authors.forename: Roy
authors.initials: R
authors.lastname: Sherwood
authors.forename: Julia A
authors.initials: JA
authors.lastname: Wendon
authors.forename: William
authors.initials: W
authors.lastname: Bernal
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood*; D005260:Female; D017583:Hemodiafiltration; D006801:Humans; D022124:Hyperammonemia / Q000097:blood / Q000175:diagnosis / Q000628:therapy*; D017093:Liver Failure / Q000097:blood / Q000175:diagnosis / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014508:Urea / Q000097:blood
chemical_list: D000641:Ammonia; D014508:Urea
keywords: Cordoba equation; ammonia clearance; haemofiltration; hyperammonaemia; ultrafiltration rate