A single dose of dalteparin effectively prevents clotting during haemodialysis

Background. A single bolus dose of LMW heparin at the start of haemodialysi s effectively prevents clot formation in the dialyser and bubble trap. Howe ver, there are few studies on the appropriate dosage of LMW heparins in hae modialysis. Therefore we examined the relationship between the anticoagulan t effect of dalteparin and clinical clotting during haemodialysis. Methods. We performed an open, prospective study on the effect of decreasin g doses of dalteparin in 12 haemodialysis patients during a total of 84 ses sions (4-4.5 h). The normally applied dose of dalteparin in each patient wa s reduced by 25% for each session down to 50% of initial dose if no clottin g was observed. Clinical clotting (grade 1-4) was evaluated by visual inspe ction after blood draining of the air trap every hour and by inspection of the dialyser after each session and compared to corresponding values for an ti-FXa activity and dialysis time. Blood flow and ultrafiltration rate were kept within narrow limits throughout the study. Results. No episodes of grade 4 clotting occurred, and no session was inter rupted. Eighteen episodes of grade 3 clinical clotting (11%) were observed in patients without warfarin treatment, none with an anti-FXa activity > 0. 43 IU/ml. Oral warfarin treatment reduced the clinical clotting, and only o ne grade 3 episode was observed in patients on warfarin therapy. Anti-FXa a ctivity and haemodialysis time were the only factors independently correlat ed to clotting in a logistic regression model. Conclusion. An anti-FXa activity above 0.4 IU/ml after 4 h of dialysis inhi bits significant clotting during haemodialysis. A bolus dose of dalteparin of 70 IUkg usually seems appropriate, but may be reduced in patients on war farin treatment. Dialysis time is an independent risk factor for clinical c lotting.