Renal Unit and 1 Department of Surgery, Stobhill Hospital, Balornock Road, Glasgow, UK
Sir,
Difficulties in creating and maintaining vascular access in haemodialysis patients often require insertion of long-term dual-lumen central venous catheters (permcaths). One of the most common problems encountered with permcaths is poor blood flow, most often secondary to the formation of a fibrin sheath around the lumens. In an autopsy series, a fibrin sheath was present in all patients after their long-term central venous catheters were removed [1]. Low-dose warfarin has been shown in a prospective randomized trial to maintain the patency of central venous catheters in patients receiving chemotherapy and in a prospective non-randomized study in patients receiving total parenteral nutrition [2,3]. We have evaluated whether low-dose warfarin has any significant effect on the long-term patency of central venous catheters in haemodialysis patients.
Haemodialysis patients were randomized on the day of de novo permcath insertion to receive either 1 mg warfarin or no warfarin. Eighteen patients were enrolled over a 2 year period. In the warfarin group, five patients had subclavian permcaths and five had internal jugular permacaths. In the non-warfarin group the patient numbers were two and six, respectively. Endpoints were catheter failure, patient death, transplantation or withdrawal of warfarin for any reason. Catheter failure was defined as the catheter being unable to provide adequate blood flow rate for haemodialysis (>250 ml/min) despite urokinase lock or single high-dose urokinase infusion. If repeated urokinase infusion was required the patient was transferred to full-dose warfarin and removed from the study.
Only three catheters were still working at the end of the study without any intervention. In the non-warfarin group there was one catheter failure and in the warfarin group there was one catheter failure and three patients required transfer to high-dose warfarin. These catheters continued to function after transfer to full-dose warfarin. Table 1 shows mean catheter survival in days for both groups of patients and compares the total survival of the patients in this study with that found by McLaughlin et al. [4] in the same unit several years previously. When analysed using log rank test, there was no significant benefit of low-dose warfarin on catheter survival. All other endpoints were not related directly to catheter function and therefore these factors were censored when the data were analysed. These included patient death, transplantation and withdrawal from the study for other reasons such as concurrent pericarditis, gastro-intestinal haemorrhage and one catheter that fell out 4 weeks after insertion.
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Despite the small numbers it is clear that there is no benefit to be gained from low-dose warfarin in prolonging the patency of dual lumen haemodialysis catheters. We feel that this an important message and should be followed up by a trial of full-dose warfarin to assess whether any benefits in terms of catheter survival outweigh the increased risk of haemorrhagic problems that is associated with full-dose warfarin.
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