Inserted through the skin and into a vein, long-term intravascular devices such as IV catheters deliver to patients a range of life-saving medications, nutrition and fluids, among other uses.
But these lifesaving devices also can provide a furtive pipeline for germs from the external world to gain access to the bloodstream of patients who often already are sick, resulting in a serious infection or even death, says University of Wisconsin-Madison professor of Medicine Dennis G. Maki.
More than 200 million intravascular devices are in use in hospitals, clinics and outpatient settings today. Although health care staff who insert them wear sterile gloves and swab patient skin with disinfectant, each year, about 500,000 patients develop an associated bloodstream infection. Of those, up to 30,000 die as a result of the infection, says Maki, who is head of the Medical School's infectious diseases section.
Maki's team has published research in the current issue of Infection Control and Hospital Epidemiology that shows that a novel method for disinfecting long-term intravascular devices over time should not have an adverse effect on their structural integrity. The research helps answer a legitimate and important concern of medical practitioners, says Maki, who conducted the work with assistant professor of medicine Christopher Crnich, associate professor of engineering physics Wendy Crone and former engineering physics student Jeremy Halfmann (BS '04).
Maki's new approach for patients with intravascular catheters is a daily "rinse cycle" with a 25- to 50-percent solution of ethyl alcohol, or medical-grade ethanol. "We fill each lumen of the catheter with the ethanol solution and then cap it off," says Maki.
"It is allowed to sit there for an hour, rapidly killing any germs that have insidiously gained access. We then simply pull it back out and reattach the IV fluids, intraveneous nutrition or intravenous medications, and the risk of later bloodstream infection caused by germs that may have gained access in the preceding 24 hours has been essentially eliminated."
This ethanol "lock" builds upon nearly a decade of Maki's own research and more recent recommendations from the Centers for Disease Control and Prevention that favor alcohol-based solutions over iodine-based disinfectants for killing germs. But before he could introduce the disinfecting system into regular clinical practice, his team needed proof that the ethanol wouldn't interact unfavorably with the catheter materials - either polyurethane or silicone - and damage them.
He turned to Crone, an expert in the mechanics of materials. Using a 70 percent ethanol solution, she and Halfmann conducted rigorous, "worst case scenario" tests. "We placed the catheters in a heated bath that mimicked the environment in the body and locked ethanol inside the catheter lumen for up to 72 days," she says.
Then they periodically removed the catheters from the bath, sectioned them and tested them to determine whether there was any change in the material's mechanical behavior. "We saw very little change in the mechanical behavior of the catheter material over the 72-day exposure time," says Crone.
This study is coupled with a large-scale ongoing comparative clinical trial Maki and Crnich are conducting at UW Hospital to rigorously test the ethanol lock's capacity to prevent IV catheter-related bloodstream infections. Together, the research projects ultimately will provide "essential results" that may enable medical personnel to use the ethanol lock technique widely and with confidence of safety, says Maki.