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In order to add convective solute transport to a recently described citrate-CVVHD protocol, we established a citrate anticoagulated continuous venovenous hemodiafiltration (citrate-CVVHDF) protocol with variable treatment dose. Citrate-CVVHD has been shown to be safe and easy to handle . Being based on dialysis, however, citrate-CVVHD primarily relies on diffusive solute transport. To also allow convective transport, we designed a new citrate-CVVHDF protocol with a postdilution hemofiltration dose.
Prospective observational study. A CVVHDF-based citrate anticoagulation protocol on the MultiFiltrate™ CRRT device (Fresenius Medical Care (FMC), Germany) using a 4% trisodium citrate solution, the dialysate fluid Ci-Ca™ Dialysate K2 (FMC), and a continuous calcium chloride (91 mmol/l) infusion. For the filtration dose we used a standard bicarbonate-buffered substitution fluid (MultiBic™; FMC) in postdilution. Ten patients on the ICU with acute kidney injury and need for RRT were included. For variable doses, patients were divided into three groups according to their body weight (1: <60 kg, 2: 60 to 90 kg, 3: >90 kg). The initial flows for dialysate/substitution fluid in the groups were 1,400/800, 1,800/1,000, and 2,200/1,200 ml/hour, blood flow 80, 100, and 120 ml/minute, citrate flow 145, 175, and 220 ml/hour, and calcium flow 32, 45, and 57 ml/minute. Citrate flow was adjusted to postfilter ionized calcium (iCa) measurements, target range 0.25 to 0.35 mmol/l. Calcium flow was adjusted to patients' systemic iCa. The treatment time was limited to 72 hours.
Eight of 10 patients reached the maximum treatment time of 72 hours without clotting. In one patient the treatment had to be stopped after 50 hours because of central venous catheter flow problems and one patient died after 54 hours. Acid-base control: mean (95% CI) pH; st-bicarbonate at 48 hours: 7.42 (7.38 to 7.44); 24.6 (21.3 to 27.8) mmol/l, and at 72 hours: 7.39 (7.35 to 7.43); 25.0 (21.3 to 27.6) mmol/l. Electrolyte control: mean (95% CI) s-sodium; s-potassium at 48 hours: 139 (137 to 141); 4.8 (4.4 to 5.2) mmol/l, and at 72 hours: 139 (137 to 142); 4.9 (4.4 to 5.4) mmol/l. Mean (95% CI) treatment dose was 41 (37 to 46) ml/kg/hour, mean (95% CI) s-urea at 48 hours: 51 (37 to 66) mg/dl, and at 72 hours: 50 (35 to 65) mg/dl.
The citrate-CVVHDF protocol allows combined hemodialysis and hemofiltration in CRRT with variable treatment dose and with the advantages of regional citrate anticoagulation. In this pilot study, in 10 patients the filter run-time in citrate-CVVHDF was remarkable and metabolic control excellent.