Ammonia Clearance with Different Continuous Renal Replacement Therapy Techniques in Patients with Liver Failure

Continuous renal replacement therapy (CRRT) can be used to treat hyperammonaemia. However, no study has assessed the effect of different CRRT techniques on ammonia clearance.

We compared 3 different CRRT techniques in adult patients with hyperammonaemia, liver failure, and acute kidney injury. We protocolized CRRT to progressively deliver continuous veno-venous haemofiltration (CVVH), haemodialysis (CVVHD) or haemodiafiltration (CVVHDF). Ammonia was simultaneously sampled from the patient's arterial blood and effluent fluid for each technique. We applied accepted equations to calculate clearance.

We studied 12 patients with a median age of 47 years (interquartile range [IQR] 25-79). Acute liver failure was present in 4 (25%) and acute-on-chronic liver failure in 8 (75%). There was no significant difference in median ammonia clearance between CRRT technique; CVVH: 27 (IQR 23-32) mL/min versus CVVHD: 21 (IQR 17-28) mL/min versus CVVHDF: 20 (IQR 14-28) mL/min, p = 0.32. Moreover, for all techniques, ammonia clearance was significantly less than urea and creatinine clearance; urea 50 (47-54) mL/min versus creatinine 42 (IQR 38-46) mL/min versus ammonia 25 (IQR 18-29) mL/min, p = 0.0001.

We found no significant difference in ammonia clearance according to CRRT technique and demonstrated that ammonia clearance is significantly less than urea or creatinine clearance.