Risk of heparin lock-related bleeding when using indwelling venous catheter in haemodialysis

Background. The indwelling venous catheter such as Dual-Cath " or Twin-Cath " is widely used in haemodialysis. Although the manufacturer recommends fi lling the catheter lumen with heparin after the dialysis session to prevent clotting, little is known about the systemic effects of such a procedure. Methods. Twenty haemodialysis patients with Dual-Cath " were studied. Dialy sis anticoagulation was achieved by injecting a bolus of dalteparin. The pa tient control ratio of activated partial thromboplastin time (aPTT) was det ermined at the end of the session immediately before and 10 min after locki ng with 2 ml of undiluted heparin (10000 U catheter). We also determined th e catheter Volume for each patient and measured aPTT immediately before and 10 min after heparin locking with this patient-specific volume. Catheter p atency was followed over a 2-week period. Results. The aPTT values determined at the end of two consecutive dialysis sessions were nearly normal, respectively 1.29 ( +/-0.17) and 1.33 ( +/-0.2 2), whereas all patients had uncoagulable blood (aPTT > 3.75) 10 min after locking with 2 ml of heparin. When catheter volumes were individually calcu lated. they were found to be substantially lower than 2.0 ml ( 1.21 +/- 0.1 2 for the arterial branch and 1.27 +/- 0.13 for the venous branch). aPTT wa s only 2.42 +/- 0.73 10 min after locking with the estimated volumes except in one patient (aPTT > 3.75). No catheter clotting was observed despite th ese smaller locking volumes. Conclusions. A risk of inducing serious bleeding does indeed exist with Dua l-Cath" heparin locking, especially in postoperative patients. This risk ca n be reduced by measuring catheter length at the time of placement in order to ensure an appropriate lock volume. Sodium citrate. polygeline, or uroki nase are possible alternatives to heparin.