University of Alabama at Birmingham continuous venovenous hemodiafiltration (CVVHDF) protocol for 0.67 and 0.5% citrate. University of Alabama at Birmingham continuous venovenous hemodiafiltration (CVVHDF) protocol for 0.67 and 0.5% citrate. Schematic representation of flow rates, dialysate, prefilter replacement fluid, calcium infusion, and dialyzer membrane. QR indicates replacement fluid rate; QD, dialysate rate; QB, blood flow rate; V, vein; PF, postfilter; iCa, ionized calcium; QFR, fluid removal rate; QE, effluent rate. Ashita J. Tolwani et al. CJASN 2006;1:79-87 ©2006 by American Society of Nephrology