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|Newsletters: Alteplase Safely Clears Thrombotic Catheter Occlusions|
Alteplase Safely Clears Thrombotic Catheter Occlusions
Most HPN consumers and caregivers have dealt with the frustration of an occluded catheter. Restoring the catheter’s function (and thus the consumer’s ability to infuse HPN, hydration, antibiotics, etc.) is not only critical to the consumer’s well being, but also to their ability to retain lifelong access. Catheters may be occluded by a thrombotic, mechanical or other obstruction. Studies show that more than half (58 percent) of catheter-related occlusions are thrombotic, resulting from the formation of thrombus within, surrounding or directly outside of the catheter. Until two years ago, these catheters were treated with urokinase.
In 1999, the Food and Drug Administration (FDA) severely limited the availability of urokinase, and since then, clinicians (and consumers) have been urgently seeking information regarding appropriate ways to use other agents to treat thrombosis-related catheter occlusion. Lifeline readers will recall Barbara McKinnon’s article in the March/April 2000 LifelineLetter which reviewed three alternative ‘clot busters:’ streptokinase, alteplase and reteplase (click here for article).
After hosting a conference to study the issue, the National Association of Vascular Access Networks (NAVAN), in cooperation with several other organizations (including the American Society for Parenteral and Enteral Nutrition), has come to the consensus that Alteplase (Genentech, Inc.) is a safe and effective treatment for thrombotic catheter occlusions. Following is some information extracted from their recently published guidelines “The Use of Alteplase (t-PA) for the Management of Thrombotic Catheter Dysfunction,” edited by William Haire, MD and Suzanne Herbst, RN, MA, published in the September 2000 Clinician. (For a complete copy of the guidelines E-mail email@example.com. Please indicate the number of copies requested and include a complete mailing address.)
Alteplase vs. Urokinase
Urokinase has been studied extensively for the treatment of occluded catheters. While early studies reported patency rates of nearly 100 percent, members of the NAVAN consensus feel the investigators did not use objective criteria or precise definitions for catheter obstruction and catheter clearance. Two more recent studies by Monturo et. al.1 and Haire et. al.2showed that urokinase returned function to 59 percent of thrombosed catheters and removed the total clot in just 32 percent of thrombosed catheters. These studies required radiographic confirmation of the presence of a thrombus and its resolution.
Clinical trials have demonstrated that t-PA restores function in about 60 to 80 percent of treated thrombosed catheters [see Table 1]. When compared with urokinase in a study by Haire, et. al.1, t-PA restored function to more catheters than did urokinase [see Table 2]. Radiographic studies confirmed the complete resolution of the occlusion in almost twice as many t-PA-treated catheters as urokinase-treated catheters. In addition, significantly fewer of the t-PA treated catheters required a second dose of drug compared with the urokinase-treated catheters.
Although clinical experience with t-PA in pediatric patients with occluded catheters is limited, preliminary data are available from two clinical trials by Maloney et. al.3and Choi et. al.4which reported rates of 88.7% and 82.3% respectively for reestablishing patency.
Dosage and Administration
Suggested procedures for treating a partial or complete thrombotic catheter occlusion are shown in Table 3. The standard t-PA concentration is 1 mg/mL. An adequate volume of the t-PA solution (usually 1-2 mL) is used to fill the catheter, and then allowed to dwell in the catheter 30 to 120 minutes. The t-PA dose can be repeated if the first try isn’t successful. If the catheter does not respond to two t-PA instillations, or if dysfunction recurs, the clinician will need to further evaluate the nature of the occlusion.
One of the drawbacks to t-PA is that it is not convenient to use. It requires refrigerated storage and must be reconstituted prior to use. Additionally, it is distributed in 50 mg doses, when only 2 mg are typically needed for catheter clearance. Once reconstituted, t-PA can be frozen for future use in individual doses for up to one month [see Table 4].
The larger distribution size means cost can also be an issue. When t-PA is repackaged in 2 mg doses its cost is comparable to urokinase, but smaller institutions may not use all 25 doses before their limited shelf life expires.
The manufacturer of t-PA (Activase®, Genentech, Inc.) is seeking FDA approval for using t-PA for catheter clearance, and hopes to have it by late summer 2001. If the drug is approved, the company will be looking into distributing the drug in a more convenient 2mg vial.
In summary, the studies of t-PA suggest that it is a well-tolerated and effective treatment to restore patency to thrombosed catheters. The consensus conference participants recommend that subsequent studies investigate other uses for t-PA, including prophylactic use to prevent catheter-related thrombotic occlusion and infection, and use with antibiotics to treat catheter-related infections.
Information from this article was adapted with permission from Gardiner-Caldwell SynerMed, the publisher of Clinician.
1. Monturo CA, Dickerson RN, Mullen JL. Efficacy of thrombolytics for occlusion of long-term catheters. J Parent Ent Nutr.1990;14(3):312-314.
2. Haire WD, Atkinson JB, Stephens LC. Urokinase versus recombinant tissue plasminogen activator in thrombosed central venous catheters: a double-blinded, randomized trial. Thromb Haemost. 1994; 72:543-547.
3. Maloney KW, Hillery CA, Nelson TJ, Gill JC. The use of aliquoted and frozen t-PA in central venous line occlusions. Blood. 1999;1(suppl):25a. Abstract 114-1.
4. Choi M, Massicotte MP, Marzinotto V, Chan AKC, Andrew M. Use of tissue plasminogen activator to clear blocked central venous lines in pediatric patients: a prospective cohort study. Blood. 1999;1(suppl):25a. Abstract 96-1.
Table 1. Patency Rates Attributed to t-PA
Table 2. Treatment of Thrombosed Catheters
Table 3. Suggested Procedure for Using t-PA
Table 4. Suggested Procedure for Aliquoting t-PA
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