Background: Minidose warfarin (1 mg/day) has been associated with a 74% reduction in the thrombosis rate of central venous catheters used in oncology patients. To determine the efficacy of minidose warfarin on late malfunction caused by thrombosis or fibrin sheath formation in tunneled, cuffed catheters (TCC) used for hemodialysis (HD), we performed a randomized, placebo-controlled trial.
Methods: One hundred five chronic HD patients with TCCs were initially randomized. Of these, 85 (warfarin 41 and placebo 44) completed the first two weeks of the protocol and were followed for the first year of TCC life or until TCC removal.
Results: Sixteen TCCs failed with late TCC malfunction, eight in each group. In a multivariate analysis, there was no significant effect of warfarin on thrombosis-free TCC survival or time to the first urokinase (UK) instillation for incipient thrombosis. The presence of a low hemoglobin (Hgb; <10.5 g/dL) or a low international normalized ratio (INR; <1.00) was significantly associated with a higher risk of late TCC malfunction (RR 5.2 and 4.0, respectively), a higher risk of incipient TCC thrombosis requiring UK (RR 2.0 and 2.8, respectively), and higher rates of UK dosing. Diabetics had a 3.6-fold higher risk of late TCC malfunction and a twofold higher risk of incipient thrombosis requiring UK, although these findings were not statistically significant. Aspirin use, race, age, number of hospitalizations, erythropoietin dose, intradialytic heparin dose, serum albumin, and the number of episodes of TCC-associated infection were not significantly associated with late TCC malfunction.
Conclusions: Thrombosis prophylaxis using fixed minidose warfarin is not efficacious in TCCs used for HD. However, the present data suggest improved TCC survival in patients with an INR> 1.00. Patients with diabetes and those with a low Hgb or INR have a higher risk of late TCC malfunction.