Removal of branched-chain amino acids and alpha-ketoisocaproate by haemofiltration and haemodiafiltration.

Venovenous haemofiltration (VVHF) and haemodiafiltration (VVHDF) were performed with a neonatal haemo(dia)filter (Miniflow 10, Hospal) on 8 anaesthetized rabbits infused with branched-chain amino acids (leucine, isoleucine and valine) and alpha-ketoisocaproate. The branched-chain amino acids (BCAA) and alpha-ketoisocaproate blood levels were close to those previously observed in neonates with maple syrup urine disease when extracorporeal blood purification was required. VVHF and VVHDF performances were assessed with two different blood flows (Qb = 8.3 and 16.6 ml/min). VVHDF was performed with four dialysate flow rates (Qd = 0.5, 1.0, 2.0 and 3.0 L/h). Within each period, clearances of the three BCAA were strictly similar. BCAA clearances obtained by VVHF were similar to ultrafiltration rates (respectively, 0.78 +/- 0.14 and 1.79 +/- 0.28 ml/min at high and low Qb; p < 0.05). The alpha-ketoisocaproate clearances obtained by VVHF were 0.39 +/- 0.17 and 0.92 +/- 0.43 ml/min at low and high Qb (not significantly different). Whatever the Qd value, the VVHDF procedures always allowed higher BCAA and alpha-ketoisocaproate clearances as compared with the corresponding VVHF period with similar Qb. BCAA clearances obtained by VVHDF with a 0.5 L/h dialysate flow were 4.1 +/- 0.5 and 5.4 +/- 0.5 mL/min at low and high Qb, respectively. The concurrent alpha-ketoisocaproate clearances were 2.5 +/- 0.8 and 2.9 +/- 1.0 ml/min.