Link between infection and thrombosis shown
Research critical to patient safety, outcomes
(Editor's note: This is the first article in a two-part series about the link between thrombosis and infection. This month, Home Infusion Therapy Management will look at the relationship between infection and thrombosis. Next month, we'll provide you with a simple four-step method to prevent both.)
Ask 100 home infusion nurses the top five complications of central venous catheters, and infection and thrombosis top every list. But Marcia Ryder, MS, BSN, RN, CNSN, a vascular access nurse consultant based in San Mateo, CA, as well as a doctoral student at the University of California in San Francisco, says it's time the industry looked at those problems as interrelated rather than as two separate complications.
"When thinking about catheter-related infection, you've got to think of thrombosis, and when you think of catheter-related thrombosis, you've got to think of infection," says Ryder. "If you don't understand this relationship, then you won't really understand prevention, management, diagnosis, or treatment of these serious problems."
The connection is scientifically complex but conceptually simple - and critical to patient welfare, says Ryder. And she's far from alone in that belief.
"Studies have shown that there is a link between thrombotic complications and infections," says Gary R. Jones, MD, associate professor of pediatrics at the Doernbecher Children's Hospital of the Oregon Health Sciences University in Portland. "This link is not recognized by a significant portion of individuals who are involved with putting in and dealing with central venous catheters."
Thrombosis contributes to infection
Fibrin, a naturally occurring protein formed by the action of thrombin on fibrinogen, is the major component of a thrombus or clot.
"When a vessel wall is damaged, a fibrinous clot forms over the damaged area to allow for tissue repair," says Ryder. "The body's response to a foreign body [catheter] in the bloodstream is similar in that the catheter becomes coated with a fibrin layer over which a thrombus may develop. So you may have a fibrinous clot on the vessel wall, and/or a fibrinous lining on the inside and outside of the catheter."
She adds that microorganisms in contact with the catheter or thrombus physicochemically bind to the fibrin. In essence, the clot gives bacteria a place to attach and colonize, a fact uncovered in recent research. But the interrelation doesn't end there, Ryder says. Fibrin not only gives bacteria a place to congregate, but also offers protection. "The bacteria remain adhered to the catheter because they secrete a sugary substance that allows them to be protected against anything we try to kill them with," says Ryder. "Then they become embedded and protected in layers of'biofilm.'"
A major oversight by nurses dealing with catheters is the failure to consider thrombosis as a cause for infection unless the catheter is occluded to the point of not working properly. "Many times, when a patient has a catheter-related infection, the catheter may be working just fine," says Jones. "In most cases of catheter-related infections, there is no problem with flushing or withdrawing. Most individuals would not think there was something related to fibrin formation within the catheter that could be playing a part in the infection."
While research is needed in the aforementioned areas, Ryder notes work needs to be done in a multitude of other areas. "We need evidence-based guidelines and standards," says Ryder. As an example, Ryder notes that one-third of the Guideline for the Prevention of Intravascular-device-related Infections promulgated by the Centers for Disease Control and Prevention (CDC) in Atlanta is simply a "no recommendation." "Recommendations cannot be made without supporting scientific evidence," she says. "That's why we need research and research dollars."
Varying standards for frequency of dressing changes is a prime example of why more research is needed. Ryder notes the following variations as an example of inconsistency that arises as the result of insufficient research:
· CDC: "No recommendation" for the frequency of dressing change. Ryder notes that while the CDC cannot draw conclusions based on existing research on how often a dressing should be changed, it is clear that a change is needed when the dressing becomes loose or wet.
· Intravenous Nurses Society (INS) in Cambridge, MA: For gauze dressings, INS recommends change every 48 hours. For transparent dressings, "at established intervals." And for antimicrobial barriers, the INS notes that "it is unknown."
· Oncology Nurses Society (ONS) in Pittsburgh: For gauze and tape, every 48 hours. For transparent dressings, every five to seven days.
(Editor's note: Jones has provided Home Infusion Therapy Management readers with a comprehensive list of references regarding recently published studies on the relationship between infection and thrombosis. The references are listed on pp. 91-92.)
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