anticoagulation was to prolong whole-blood activated coagu- lation time by 150%  25%. It also is interesting that in our study, mean compression time was similar to that of the present study (14.7  5.8 minutes) despite the higher doses of UFH. Brunet et al 1 confirm the large interindividual variability in UFH pharmacokinetics, but do not provide full clinical data about the grade of extracorporeal circuit clot- ting at the end of the session (coagulated fibers in the dialyzer, clots in the air bubble trap, and so on). We believe that if there is still a place for wide use of UFH, this might be in the future as anticoagulation for superflux HD 5 or high-volume on-line hemodiafiltration, in which increased procoagulatory activity and the very large pores of the dialyzers may result in less efficient anticoagulation with single-dose LMWHs compared with UFH. 6 Costas Fourtounas, MD, PhD University of Patras Patras, Greece ACKNOWLEDGEMENTS Support: None. Financial Disclosure: None. REFERENCES 1. Brunet P, Simon N, Opris A, et al: Pharmacodynamics of unfractionated heparin during and after a hemodialysis session. Am J Kidney Dis 51:789-795, 2008 2. Ouseph R, Ward RA: Anticoagulation for intermittent hemodialysis. Semin Dial 13:181-187, 2000 3. Walenga JM, JeskeWP, Prechel MM, Bacher P, Bak- hos M: Decreased prevalence of heparin-induced thrombocy- topenia with low-molecular weight heparin and related drugs. Semin Thromb Hemost 30:S69-S80, 2004 (suppl 1) 4. Koutsikos D, Fourtounas C, Kapetanaki A, et al: A cross-over study of a new molecular weight heparin (Logipa- rin) in hemodialysis. Int J Artif Organs 19:467-471, 1996 5. Ward RA: Protein-leaking membranes for hemodialy- sis: A new class of membranes in search of an application? J Am Soc Nephrol 16:2421-2430, 2005 6. Krieter DH, Falkenhain S, Collins G, Lemke HD, Canaud B: Clinical cross-over comparison of mid-dilution hemodiafiltration using a novel dialyzer concept and post- dilution hemodiafiltration. Kidney Int 67:349-356, 2005 © 2008 by the National Kidney Foundation, Inc. doi:10.1053/j.ajkd.2008.06.028 IN REPLY TO ‘PHARMACODYNAMICS OF UNFRACTIONATED HEPARIN DURING AND AFTER A HEMODIALYSIS SESSION: THE IMPACT OF THE ADMINISTERED DOSE’ We thank Dr Fourtounas for his letter. 1 We completely agree that we used a low total dose of unfractionated heparin (UFH; 50 IU/kg for a 4-hour session, which represents 25 IU/kg during the first hour, 12.5 IU/kg/h during the next 2 hours, and no heparin administered during the last hour). These doses were at the lower level of the range recommended by Ouseph and Ward, 2 who suggested a dose of 25 to 30 IU/kg followed by an infusion of 1,500 to 2,000 IU/h. Our pharmacokinetic analysis suggested that the doses used in our study are efficient and safe. As briefly mentioned in our report, no clotting of dialyzers and blood tubing was observed during the study. Moreover, we should emphasize that in our daily practice, most of our patients could be treated with even lower heparin doses without coagulation of the extracorporeal circuit. These low doses explain the very interesting pharmacokinetics of UFH in hemodialysis patients. At doses less than 100 IU/kg, the disappearance of heparin activity is exponential because of its binding to endothelium and macrophages. 3,4 This is an important difference from low-molecular-weight heparins, which are cleared mainly by the renal route. We also agree with Dr Fourtounas to say that UFH could be useful to accu- rately adjust anticoagulation, not only in patients with bleeding risk, but also in patients receiving such treat- ments as hemodiafiltration. 5 Philippe Brunet, MD Valérie Faure, MD Assistance Publique-Hôpitaux de Marseille Aix-Marseille Université Marseille, France Nicolas Simon, MD Laboratoire de Pharmacologie Médicale et Clinique Aix-Marseille Université Marseille, France ACKNOWLEDGEMENTS Support: None. Financial Disclosure: None. REFERENCES 1. Fourtounas C: Pharmacodynamics of unfractionated heparin during and after a hemodialysis session: The impact of the administered dose. Am J Kidney Dis 52:805-806, 2008 (letter) 2. Ouseph R, Ward RA: Anticoagulation for intermittent hemodialysis. Semin Dial 13:181-187, 2000 3. de Swart CA, Nijmeyer B, Roelofs JM, Sixma JJ: Kinetics of intravenously administered heparin in normal humans. Blood 60:1251-1258, 1982 4. Hirsh J, Raschke R: Heparin and low-molecular- weight heparin: The Seventh ACCP Conference on Anti- thrombotic and Thrombolytic Therapy. Chest 126:S188- S203, 2004 (suppl 3) 5. Klingel R, Schaefer M, Schwarting A, et al: Compara- tive analysis of procoagulatory activity of haemodialysis, haemofiltration and haemodiafiltration with a polysulfone membrane (APS) and with different modes of enoxaparin anticoagulation. Nephrol Dial Transplant 19:164-170, 2004 Correspondence 806