Computer program to prescribe acetate-free biofiltration as a continuous renal replacement therapy: theoretical...

We describe the theoretical features and in vivo assay of an original computer-based program, which describes Na and HCO3 kinetics with acetate-free biofiltration performed as a continuous veno-venous renal replacement therapy (CVVAFB). In 14 patients, CVVAFB sessions were performed as follows. Machine Hospal Prisma, membrane AN69 0.9 m2, blood circuit Hospal M100 pre Set, dialysate bags of electrolyte solution with basic composition of: Na 139 mEq/L, K 2 mEq/L, Ca 3.0 mEq/L, Mg 2 mEq/L, Cl 146 mEq/L, and glucose 5.5 mmol/L. Predilutional infusion bags of 167 mEq/L of NaHCO3 solution (Hospal Biosol). To guide the prescription of the dialysate (QD) and the infusate (QInf ) flow rates we designed a suitable computer program, which calculated Na and HCO3 kinetics and predicted their plasma profiles at equilibrium. Prescribed flow rates were QB 150 ml/min, QD 1636 +/- 42 ml/hr, Q Inf 639 +/- 74 ml/hr and ultrafiltration (UF) rate 110 +/- 41 ml/hr. During CVVAFB, plasma profiles of HCO3 and Na became stable after 24 hr. With HCO3 , the average predicted and observed plasma levels at equilibrium were 27.1 +/- 1.5 and 27.3 +/- 1.5 mEq/L, respectively (p=ns); with Na, the predicted and observed levels at equilibrium were 140.2 +/- 1.8 and 141.3 +/- 1.7 mEq/L, respectively (p=ns). There was a good correlation between predicted and observed values for both Na (p<0.01, r=0.78) and HCO3 (p<0.01, r=0.87). These results confirmed the reliability of our mathematical model for CVVAFB. A Long-term trial is needed to obtain more information on its clinical effects and compare CVVAFB with other continuous renal replacement therapy techniques.