NDT Advance Access originally published online on September 19, 2007
Nephrology Dialysis Transplantation 2008 23(4):1465-1466; doi:10.1093/ndt/gfm604
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New strategies in haemodialfiltration (HDF)––prospective comparative analysis between online mixed HDF and mid-dilution HDF
E-mail: krieter_d{at}medizin.uni-wuerzburg.deSir,
The report by Feliciani et al. [1] on the comparison of online mixed haemodialfiltration (HDF) and mid-dilution HDF caused several concerns as to the validity of their results. Their decision, which was based on a misinterpretation of our own, earlier published work [2], not attempting to optimize anti-coagulation for mid-dilution HDF, may have resulted in insufficient heparin dosing and, subsequently, in very high pressures and reduced clearances, due to increasingly clotting of fibers. The nearly instantaneous pressure rise suggests significant clotting at the outset of treatment. As a consequence of the unique blood flow-path configuration of the Nephros MD 190 filter, which is very sensitive to clotted fibres, and the procoagulatory effect of intense convection [3], it is highly advisable to comply with current recommendations for anti-coagulation in HDF to keep the device patent [4]. Therefore, it would be important to learn more about the applied heparin doses and the achieved effects on coagulation during HDF treatments performed within the study of Feliciani et al.
In our own tests, in four patients on mid-dilution HDF with the larger Nephros MD220 filter (surface area 2.2 m2), considerably lower pressures (maximum 767 mmHg) were observed at the arterial port of the device, when more rigorous operating conditions were chosen (Figure 1). Compared to Feliciani et al., both blood and substitution flow rate were set higher, being 400 and 200 ml/min, respectively. The activated clotting time ranged between 254 s at 30 min and 190 s at the end of treatment (at baseline 123 s). We also confirmed the findings from a very recently published study [5], reversing the configuration of the blood tubing, i.e. the connection of the arterial line to the venous port of the MD filtre and vice versa, leading to even lower filter inlet pressures with a peak of 649 mmHg, despite otherwise unchanged operating parameters (Figure 2). In case of pressure-related problems, the reverse configuration can be recommended without significantly lower β2-microglobulin plasma clearances (at 30 and 220 min 119 ± 13 and 107 ± 14 ml/min in reverse vs 127 ± 11 and 121 ± 21 ml/min in standard configuration, respectively) at similar albumin loss (1.5 ± 0.5 vs 2.2 ± 0.7 g/4 h session, respectively). In addition, it is self-evident that the blood flow rate has an important effect on the most critical inlet blood pressure of the MD220 device, as demonstrated in Figure 2.
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According to our findings and experience, mid-dilution HDF with the Nephros MD220 filter is a safe and highly effective therapy mode, provided that adequate operating conditions have been chosen.
Conflict of interest statement. D.H.K. and B.C. have received research grant support from Nephros, Inc.
1 University of Würzburg Department of Cardiology Division of Nephrology Josef-Schneider-Str. 2 97074 Würzburg Germany 2 University of Montpellier Lapeyronie Hospital Department of Nephrology 371, Av. du Doyen Gaston Giraud 34295 Monpellier Cedex 5 France
References
- Feliciani A, Riva MA, Zerbi S, et al. New strategies in haemodiafiltration (HDF): prospective comparative analysis between on-line mixed HDF and mid-dilution HDF. Nephrol Dial Transplant (2007) 22:1672–1679.
[Abstract/Free Full Text] - Krieter DH, Falkenhain S, Chalabi L, et al. Clinical cross-over comparison of mid-dilution hemodiafiltration using a novel dialyzer concept and post-dilution hemodiafiltration. Kidney Int (2005) 67:349–356.[CrossRef][Web of Science][Medline]
- Klingel R, Schaefer M, Schwarting A, et al. Comparative analysis of procoagulatory activity of haemodialysis, haemofiltration and haemodiafiltration with a polysulfone membrane (APS) and with different modes of enoxaparin anticoagulation. Nephrol Dial Transplant (2004) 19:164–170.
[Abstract/Free Full Text] - Canaud B, Krieter D. Hemodiafiltration and hemofiltration. In: Handbook of Dialysis—Daugirdas JT, Blake PG, Ing TS, eds. (2007) 4th edn, Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins. ; 265–275.
- Santoro A, Ferramosca E, Mancini E, et al. Reverse mid-dilution: new way to remove small and middle molecules as well as phosphate with high intrafilter convective clearance. Nephrol Dial Transplant (2007) [Epub ahead of print].
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