V.2 Prevention of clotting in the HD patient with normal bleeding risk Guideline V.2.1 A. In patients without elevated bleeding risk low-dose unfractionated heparin or LMWH

A. In patients without elevated bleeding risk low-dose unfractionated heparin or LMWH can be used to prevent clotting of the extracorporal system during haemodialysis. A. Because of proven safety (evidence level: A), equal efficacy (evidence level: A), and easy handling (evidence level: C) the use of LMWHs is to be preferred over unfractionated heparin. Other benefits of LMWH are an improved lipid profile (evidence level B), less hyperkalaemia (evidence level: B) and less blood loss (Evidence level: C). Unfractionated heparin binds to the heparin-binding site of antithrombin-III (AT-III). This induces conformational changes of AT-III resulting in the transition of AT-III from a slow into a rapid inactivator of clotting factors such as factor Xa and to a lesser extent XIIa, Xia, and IXa. In addition, heparin is an indirect inhibitor of thrombin, for which simultaneous binding of AT-III and thrombin is mandatory. This requires lengths of heparin molecules exceeding 18 monosaccharide units. At present, routine anticoagulation with heparin is performed with low-dose heparin. Heparin (half-life of"1.5 h) can be best given by administration of a loading dose (approximately 50 IUukg), followed by continuous infusion (800–1500 IUuh) [15–20]. The efficacy of heparin treatment can be evaluated by measurement of the activated partial thromboplas-tin time or the whole-blood clotting time. A prolonga-tion of the APTT or whole-blood clotting time to 150% of their pre-dialysis values is recommended [20]. Individual dosing schedules can reduce bleeding complications [21–23], but this usually requires mathe-matic modelling which is inconvenient. Opatrny et al. [24] performed a randomly prospective study in which they investigated the effect of rinsing the dialyzer with saline with or without heparin, and comparing low-flux and high-flux polysulfone dialyzers. Blood was sampled at the haemodiayzer inlet before haemo-dialysis and at 15, 60, and 240 min of haemodialysis. No difference in activation of the coagulation cascade Fig. 1. Overview of the coagulation cascade (PLsphospholipid). 64 SECTION V: Chronic intermittent haemodialysis and prevention of clotting in the extracorporal system