Solution sought for the best way to keep catheters from clogging
Solution sought for the best way to keep catheters from clogging
Providers look to TPA to replace Urokinase
With the future availability of Urokinase still in doubt, providers across the country are well on their way to finding a replacement. Now there seem to be two leading candidates. This month, in the first of a two-part series, Home Infusion Therapy Management looks at one option — Alteplase (TPA). Next month, we will feature a provider who chose another path: Streptokinase.
The Food and Drug Administration has yet to allow Abbott to release further lots of Urokinase to market, and neither the federal government nor Abbott have any timetable as to when it may be released.
Cathy Parker, an RN with the Vascular Access Device Consult Service, National Institutes of Health (NIH) in Bethesda, MD, notes that the NIH has chosen TPA to declot catheters.
"When the Urokinase shortage occurred, we talked with the pharmacy and interventional radiology to discuss what we were going to do," says Parker. "We talked about other drugs, and it was quickly decided that Streptokinase was not appropriate because of its history of allergic reactions. TPA was a much better alternative."
TPA was first considered, based on a published study comparing Urokinase and TPA.1 After reading that study, conducting a literature search, and having NIH pharmacists call oncology centers nationwide to find out what they were doing, TPA became the clear choice, according to Parker.
Through collaborative efforts of the Vascular Access Device Consult Service and the pharmacy, the NIH developed a new procedure for declotting catheters using 2 mg TPA/2 ml based on the Haire study. (See p. 98 for the full NIH procedure.)
Thus far, the NIH has used TPA on nine patients.
"I haven’t heard of any adverse reactions," says Parker. "On a couple of occasions it hasn’t worked, but after a cathetergram in each situation we found that there was usually something else going on — the catheter was malpositioned, the catheter was broken, or the TPA wasn’t even able to get into the catheter. I’m not aware of a situation in which TPA didn’t work that there wasn’t some other mitigating factor."
As a result, the NIH has not yet altered its procedure. Parker adds that the TPA tracking forms are still coming in, so further evaluation is needed. (See NIH TPA tracking form, p. 100.)
Making adjustments
Deaconess Home Medical Equipment and Infusion, in Evansville, IN, is also using TPA to declot catheters with slightly different success.
"We had talked about TPA here, but we never really looked into it until recently," says Ann Williams, RN, CRNI, an infusion educator nurse for Deaconess and an IV nurse consultant.
With Urokinase unavailable, Williams notes that Deaconess has lost some lines. "We’ve lost lines that we had to replace," she says. "We’ve tried to open them using the larger syringes and heparin the same way we used Urokinase, but it was few and far between that it worked."
Much like the NIH, Deaconess also considered Streptokinase but eventually looked elsewhere.
"The hospital [Deaconess Medical Center] was using Streptokinase, and they had a series of adverse reactions from it. That really prompted us to look for something else," says Mark Roy, PharmD, an infusion pharmacist for Deaconess. "To the best of my knowledge, they were considered serious adverse reactions. They had only used Streptokinase three or four times to unlock the lines, and I think in three of the four cases they had adverse reactions."
Once Streptokinase was ruled out, Deaconess found itself on the same track as NIH in that it turned to TPA. Williams used the NIH’s procedure as a basis for Deaconess’ procedure.
"I adapted our procedure from the NIH’s, and basically catered it more or less to our own needs without making any major changes," she says.
Because TPA is currently available only in 50 mg vials, mixing syringes became an issue.
"We pulled a couple of articles, and the biggest thing for us was mixing up a large vial of TPA and then perhaps not using it all," says Roy. "Now, we mix up a 50 mg vial and go with 1 mg/ml, so there are 50 syringes we mixed up and froze."
He adds that TPA, when frozen, is good for 90 days. When mixing this way, the cost of TPA is almost identical to what Deaconess was paying for Urokinase.
"When we mixed up the 50 mg vial of Alteplase, each mg ran $27.50," he says. "The Urokinase was $56 per 5,000 unit vial, which was one dose. But some people are using TPA in 2 mg/ml concentration, and then it is about the same."
The 1 mg/ml concentration was based on European studies that Roy found after conducting a literature search on TPA. However, Roy and Williams point out that an alteration in their procedure could be on the horizon.
"We are going to document our success rate; if we have a problem, we will increase the concentration up to 2 mg/ml," says Williams.
Variations on a theme
Thus far, Deaconess has used its TPA procedure on four occasions — twice each on two patients.
"We’re less than convinced at this point," says Roy. "We saw no adverse reactions. But the very first patient we used it on, the TPA opened the line but the line closed off again in three days. We were not able to aspirate blood from a Portacath. We were still able to infuse but we couldn’t aspirate."
For the second patient it took two applications; although there was some blood return, it didn’t work as well as hoped. But much like the NIH, it appears there may have been an outside factor with both patients.
"They brought that patient in for a dye study, and the radiologist sent her back home because he was meeting some resistance also, but the dye study was negative," says Williams. "We may be looking at a precipitate or something like that."
For the first patient, in which the line closed off after three days, Williams says a dye study showed a fibrin sheath in the catheter itself, beyond the port.
"We opted to use the 1 mg/ml, but we used a larger volume," she says. "We also let it dwell longer. We made some changes in our variables and on that particular occasion, it opened the line on a Friday, and on Monday they were still getting blood flow for lab work. It’s just a matter of determining which variable made the difference."
As a result of the infusion provider’s experiences, the medical center is also switching to TPA.
"I think the literature really supports the use of TPA, and some of the literature says it could be considered more effective than Urokinase," says Roy. "We’re hoping that in the long run we will get more lines open."
Williams echoes those comments, and adds that it’s simply a change that providers will have to consider.
"[Using something other than Urokinase] is something that nursing has to get beyond," she says. "TPA is as safe or safer than Urokinase from everything we read about it. And we’re using much smaller doses than are used for heart attack patients."
Reference
1. Haire W, Atkinson J, Stephens L, et. al. Urokinase vs. recombinant tissue plasminogen activator in thrombosed central venous catheters: A double-blinded, randomized trial. Thromb Haemost 1994; 72:543-547.
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