Do Ultrasound Probes Require High-Level Disinfection?

While a few ultrasound procedures suggest increased instances of patient infections due to low-level disinfection techniques, statistically, results from peer-reviewed studies do not confirm this idea.

Point-of-care ultrasound use has increased into many innovative clinical applications for many medical specialty areas. The inference has been made that increased risk of patient infections have been found with this ultrasound use. However, according to Oliver D. Kripfgans, PhD, FAIUM, who is a research associate professor of radiology, biomedical engineering, and applied physics at the University of Michigan, this idea of increased patient infections has not been verified by the peer-reviewed literature. Infection Control Today® (ICT®), spoke with Kripfgans about this topic and whether high-level disinfection techniques are appropriate.

This is the first in a series of articles based on ICT®'s exclusive interview with Kripfgans. The second segment is here. The third segment is here. The fourth segment is here

Infection Control Today® (ICT®): Over the past 2 decades, clinical applications for point-of-care ultrasound have expanded into many medical specialty areas. Has this increased usage correspondingly increased the risk of patient infections?

Oliver D. Kripfgans, PhD, FAIUM: Of course, the number of infections can increase if you have greater use of medical procedures that are known to be related to infection risks. Also, as more people are involved in performing the procedures, there may be an increase in less-experienced users that can give rise to more infections. But what’s important is whether these infections are caused by the use of ultrasound, and whether they are related to cleaning and disinfection procedures. In effect, we want to know what are the root causes of those infections.

Whether users are in the traditional domains of ultrasound—radiology or emergency care, for instance—or in 1 of the specialties where ultrasound is a relatively new technique, they should become familiar with the relevant guidelines from health professional organizations. They should be able to rely on those guidelines to understand what kind of cleaning and disinfection is appropriate for particular ultrasound procedures. There are many different types of ultrasound procedures, so it makes sense that there cannot be just 1 method for cleaning and disinfection. The method used for cleaning and disinfection must always correspond to the application.

So users have relied on guidelines from such professional associations as the American College of Emergency Physicians (ACEP), the American Institute of Ultrasound in Medicine (AIUM), or the Radiological Society of North America (RSNA). It is helpful when users can get clear and consistent guidance from such organizations, but it’s not helpful when they get differing information because that produces confusion and a heightened level of uncertainty about which procedure is the correct one to be followed.

ICT®: There have been periodic reports of patient infections related to point-of-care ultrasound use. Have the root causes of such instances been identified?

OK: I always ask people to send me references to ultrasound-related infections that have been reported in the peer-reviewed literature, and there have been a few such reports. Some of them refer to instances where cleaning and disinfection simply wasn’t performed, or wasn’t performed as instructed, or where a protective cover or barrier was required, but wasn’t used. Other publications report cases in which the infections resulted from the use of contaminated gel.

Out of all the cases of ultrasound-related patient infection reported to me, just 1 claimed to have involved a percutaneous procedure that resulted in a patient death. But in fact, the death came after an endocavitary examination—not a percutaneous procedure—where an improperly reprocessed transesophageal ultrasound probe is thought to have been contaminated with hepatitis B. And even the authors of that article were less than certain about the relationship of the ultrasound procedure to the patient’s infection, saying only that it may have been associated with the death.

I have reviewed all the literature available to me, including an extensive number of journal articles. In all of that literature, not a single publication revealed a patient infection that resulted from the use of low-level disinfection instead of high-level disinfection. Where all other procedural steps were performed correctly—using appropriate gel together with a transducer cover or barrier, for instance—there are no reports of death or other adverse health outcomes that have been traced to the use of low-level disinfection techniques.

ICT®: Have there been any published statistics about patient infections resulting from percutaneous procedures such as ultrasound-guided peripheral IV insertions?

OK: There are a couple of studies of that type, and 1 of them is very comprehensive. In that case, the researchers studied 800 patients who underwent a peripheral IV catheter insertion. Roughly half of the procedures were performed under ultrasound guidance, while the other half were performed without guidance. In the group with ultrasound guidance there were 2 infections, while the group without ultrasound guidance had 3 infections—a statistically meaningless difference. Those results tell me that there is a baseline likelihood of infection whenever a peripheral IV catheter insertion is performed, but that using ultrasound guidance does not result in any increase in risk.

The authors of that article recently published a clarification of the cleaning and disinfection methods used in their study, confirming that they applied low-level disinfection techniques of the type recommended in the Intersocietal Position Statement. That clarification effectively confirms that there is no increased risk of infection when low-level disinfection is used to process transducers used in percutaneous procedures.

That publication represents a very strong statement, for a couple of reasons. First, the study included a large number of patients that pushes its findings out of the realm of the merely anecdotal and into the realm of statistical significance. And second, the researchers used a low-level disinfecting agent of a type that is commonly available in many health care settings and does not represent a burden on the organization. Such a study sends a very strong signal to providers that they can use common low-level disinfecting agents that are effective against bloodborne pathogens, rather than having to use an expensive and somewhat uncommon processing system to perform high-level disinfection.

In short, there is no indication in the literature to justify requirements for high-level disinfection of transducers used in percutaneous procedures.