Infections Associated with Use of Ultrasound Transmission Gel: Proposed Guidelines to Minimize Risk

Affiliations: 1. Department of Epidemiology, Beaumont Health System, Royal Oak, Michigan; 2. Oakland University William Beaumont School of Medicine, Royal Oak, Michigan. Received April 26, 2012; accepted July 21, 2012; electronically published October 23, 2012. 2012 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2012/3312-0008$15.00. DOI: 10.1086/668430 Ultrasound transmission gel (USTG) is used in a variety of healthcare settings for both diagnostic and interventional procedures. Its potential role as a vehicle for spread of infections to patients is frequently overlooked. It has been shown on multiple occasions that USTG can become contaminated with bacteria, leading to significant outbreaks of infection among patients. It is incumbent upon all medical professionals to be aware of the potential risks these products pose to patients. Manufacturers of USTG should label products clearly as to their intended use. Producers of medical devices where USTG is likely to be used should provide explicit instructions on the type of USTG recommended and methods of use. Finally, standardized professional society guidelines would enhance patient safety and improve outcomes. On the basis of our recently described outbreak of infections associated with intrinsically contaminated ultrasound gel and a review of all other clusters, we would like to describe the differences between gels and propose guidelines for use of both nonsterile and sterile ultrasound gel. USTG is available from multiple manufacturers and comes in a variety of formulations and dispenser sizes, often without clearly defined differences between products or suggested uses. A review of one manufacturer’s website found 6 separate USTGs available for purchase, although it was not made clear what significant differences existed between products or if there were specific intended uses for them. Although these gels are often considered bacteriostatic because of components such as parabens or methyl benzoate, one study demonstrated that an ultrasound gel had no intrinsic antimicrobial properties and could function as a medium for bacterial growth. Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus were all demonstrated to survive in USTG in another in vitro study. The term “bacteriostatic” should not be used unless the product meets defined requirements to prove this. Contaminated USTG has been associated with outbreaks of infection due to a variety of procedures and microorganisms (Table 1). In all circumstances, the outbreaks were aborted after a switch to single-dose sterile gel. Our more recent report of cases of respiratory infections and colonizations with P. aeruginosa strongly suggested that gel contaminated at or around the time of manufacture was associated with infections. In this series, 16 patients were found to have P. aeruginosa in their respiratory tract after undergoing cardiovascular surgery. Laboratory isolates for 10 patients were saved, and all 10 proved to be more than 99% similar by molecular typing via repetitive extragenic palindromic polymerase chain reaction (rep-PCR). This surgery included the use of an intraoperative transesophageal echocardiogram (TEE) that utilized USTG as a conducting agent. The TEE probes were culture negative, but cultures of in-use multidose bottles of gel as well as sealed, unopened bottles of gel grew P. aeruginosa, which were also more than 99% similar to the outbreak strain by rep-PCR. Procedures utilizing USTG can range from noninvasive studies (such as transthoracic echocardiography, bladder scans, and vascular scans), to those with mucous membrane contact (such as TEE and transvaginal ultrasonography), to frankly invasive procedures (such as transrectal prostate biopsy [TRPB], thyroid biopsy, epiaortic ultrasonography [EAU], and stereotactic breast biopsies). As such, the Spaulding classification scheme can be applied to guide clinicians in making decisions regarding proper disinfection and sterilization of devices on the basis of the risk of infection involved with use of the item. By this scheme, scanning devices used for noninvasive procedures could be considered “noncritical devices” because of their contact with intact skin. Likewise, diagnostic studies using TEE or TRPB would require “semicritical” disinfection because of contact with mucous membranes. EAU transducers are required to be sterile, as they are introduced directly into the surgical field. On the basis of the Spaulding classification scheme, how does one define the appropriate use of USTG for procedures? Any procedure involving sterile skin preparation would likely also require sterile USTG. Sterility is not a necessary require-