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Abstract: PO1099

Excessive Unfractionated Heparin Dosing During Hemodialysis Explained by Access and Discordance Between Activated Clotting Time and Activated Partial Thromboplastin Time

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • De Troyer, Marijke, Vrije Universiteit Brussel, Brussels, Belgium
  • Wissing, Karl Martin, Vrije Universiteit Brussel, Brussels, Belgium
  • De Clerck, Dieter, Vrije Universiteit Brussel, Brussels, Belgium
  • Tonnelier, Annelies, Vrije Universiteit Brussel, Brussels, Belgium
  • Cambier, Marie-Laure, Vrije Universiteit Brussel, Brussels, Belgium
  • Francois, Karlien, Vrije Universiteit Brussel, Brussels, Belgium

Recommendations and practice patterns for heparin dosing during hemodialysis show substantial heterogeneity and are scantly supported by evidence. This study was designed to investigate factors conditioning the dose of unfractionated heparin (UFH) prescribed during maintenance hemodialysis.


We performed a cross-sectional study assessing UFH dosing, coagulation tests - activated partial thromboplastin time (aPTT) and activated clotting time (ACT) before dialysis start, 1h after start and at treatment end (4h) - and post dialysis measurement of residual blood compartment volume of the dialyzer (“total cell volume”) during a single hemodialysis session.


94 patients, 57% male, with a median dialysis vintage of 34(6-84) months were dialyzed using a total UFH dose of 9271±4066 (range 3000-23050) IU/session (127±58 IU/kg/session). Use of a central venous catheter (n=48, 51%) was associated with higher UFH loading dose (51±22 vs 37±17 IU/kg in patients with arterio-venous (AV) access; p<0.001) and higher total UFH dose (158±55 vs 89±32 IU/kg; p<0.001). Dialysis sessions using catheters with recent history of thrombotic dysfunction tended to use higher total doses of UFH (174±61 vs 147±49 IU UFH/kg) (p=0.09).
Compared to baseline values, aPTT increase was significantly higher than ACT increase both 1h (4.7-fold, 95%CI 4.2-5.3 vs 2.0-fold, 95%CI 1.7-2.3) and 4h after dialysis start (3.6-fold, 95%CI 3-4.2 vs 1.6-fold, 95%CI 1.3-1.9) (p<0.0005). One and 4h after dialysis start, 75% and 51% of patients presented a >2.5-fold increase in aPTT. Among patients with aPTT increase >2.5-fold at 4h, 84% had an ACT increase of ≤2.5-fold and 52% of ≤1.8-fold (p<0.001). No clinically significant clotting of the extracorporeal circuit was noted during the studied sessions. Dialyzer’s total cell volume was reduced with a median of 9% (6-21%) without significant effect of UFH dose, aPTT or ACT measurements and catheter use. UFH dose, aPTT, ACT and catheter use were not associated with spKt/Vurea either.


Routine clinical practice of UFH dose adaptations based on ACT measurements results in frequent over-anticoagulation according to aPTT results. Higher doses of UFH are used in patients with hemodialysis catheters without evidence that this reduces dialyzer clotting or improves urea clearance.


  • Government Support - Non-U.S.