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

Abstract

<b><i>Introduction:</i></b> 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. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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, <i>p</i> = 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, <i>p</i> = 0.0001. <b><i>Conclusion:</i></b> 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.