Prophylactic Warfarin and Central Venous Catheters |
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| Question: |
Recently I have noticed more patients with central venous catheters being placed on warfarin (coumadin). Why is this necessary? Should this be used for all types of central venous catheters? What lab results should we be looking for on the coagulation studies? |
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| Answer: |
Warfarin in small doses is used to prevent catheter-related venous thromboses. It has been reported in several studies in adult and pediatric oncology patients and pediatric patients receiving parenteral nutrition. [Klerk, 2003 #919] [Newall, 2003 #920]
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| In the first published study, 40 oncology patients with an implanted port did not receive warfarin while 42 were randomly assigned to receive 1 mg of warfarin per day. In the warfarin group, there were four patients with thrombosis diagnosed by venogram while the group without warfarin had 15 patients with venogram-proven thrombosis. [Bern, 1990 #164] Although this study randomized the patients to the two groups, catheter tip location, a major factor influencing thrombus development, included both superior vena cava and innominate veins. |
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| Several additional studies of small groups of oncology patients with tunneled catheters and implanted ports have reported a reduced risk of venous thrombosis with low dose warfarin. One drug interaction has been reported with using warfarin in patients receiving fluorouracil chemotherapy protocols. [Masci, 2003 #918] Warfarin has been shown to be beneficial in patients with cancer-induced thromboses, especially those with solid tumors. |
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| Another study reported a very low rate of physician compliance with using low-dose warfarin They initially found that only 10% of patients were prescribed prophylactic warfarin. After a physician notification program, the rate increased to 20%. The next step was to create a protocol for prescription by a nurse practitioner unless there was some contraindication. This last step yielded documentation of a statiscally significant reduction in thrombus rates. [Carr, 2000 #637] |
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| No studies on using prophylactic warfarin in patients with PICCs can be found. The available studies also present many challenges because there is no consistent reporting of catheter insertion site, catheter tip location or type of catheter. |
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| All studies report measuring the international normalization ratio (INR) and adjusting the dose to maintain the INR at 1.5 or greater. A large study compared low-intensity warfarin therapy to conventional or moderate intensity where the INR was targeted between 2 and 3. In this group of 738 patients randomly assigned to each group, 16 in the low-intensity group had a recurrent venous thromboembolism compared with 6 in the moderate intensity group. Major bleeding events occurred equally in both groups. [Kearon, 2003 #921] |
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| While there is a large amount of interest in anticoagulants as a way to prevent catheter-related thrombosis, there are very few conclusive answers from large studies. This therapy has been used more extensively in oncology patients; therefore it is difficult to draw general conclusions for other patient populations. Dosing of warfarin should be very individualized due to many genetic variations in how it is metabolized. |
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| This article was originally published in the Catheter Connection column of the Journal of Vascular Access Devices. For more information about the National Association of Vascular Access Networks, visit http://www.navannet.org |
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