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 filling 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. Dialysis anticoagulation was achieved by injecting a bolus of dalteparin. The patient/control ratio of activated partial thromboplastin time (aPTT) was determined at the end of the session immediately before and 10 min after locking with 2 ml of undiluted heparin (10,000 U/catheter). We also determined the catheter volume for each patient and measured aPTT immediately before and 10 min after heparin locking with this patient-specific volume. Catheter patency 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 (+/-0.22), whereas all patients had uncoagulable blood (aPTT >3.75) 10 min after locking with 2 ml of heparin. When catheter volumes were individually calculated, they were found to be substantially lower than 2.0 ml (1.21+/-0.12 for the arterial branch and 1.27+/-0.13 for the venous branch). aPTT was 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 these smaller locking volumes.

Conclusions: A risk of inducing serious bleeding does indeed exist with Dual-Cath heparin locking, especially in postoperative patients. This risk can be reduced by measuring catheter length at the time of placement in order to ensure an appropriate lock volume. Sodium citrate, polygeline, or urokinase are possible alternatives to heparin.