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Cleaning Stethoscopes with Ethanol-based Cleaner vs. Isopropyl Alcohol Which Is Better?
Abstract & Commentary
By Richard Wall, MD, MPH, Pulmonary Critical Care & Sleep Disorders Medicine, Southlake Clinic, Valley Medical Center, Renton, WA. Dr. Wall reports no financial relationship to this field of study. This article originally appeared in the September 2009 issue of Critical Care Alert. It was edited by David J. Pierson, MD, and peer reviewed by William Thompson, MD.
Synopsis: This study showed that cleaning a stethoscope with an ethanol-based foam hand cleaner is as effective as wiping it with an isopropyl alcohol pad.
Source: Lecat P, et al. Ethanol-based cleanser versus isopropyl alcohol to decontaminate stethoscopes. Am J Infect Control 2009;37:241-243.
For many years, infection-control experts have focused on improving the hand-hygiene habits of health care providers. This before-and-after observational study is an extension of that work, namely focusing on the hygiene of stethoscopes used for routine patient care. The study compared the effectiveness of cleaning stethoscopes with two different agents a foam ethanol-based hand cleaner (EBC) vs. isopropyl alcohol pads (IPA). The objective was to determine the effectiveness of each agent in reducing bacterial contamination of stethoscope diaphragms.
The study was conducted in a 600-bed academic medical center. Stethoscopes were taken from a convenience sample of 99 providers (55 nurses, 42 physicians, two students) on general medical floors. Stethoscopes were cultured by pressing the diaphragm onto a blood agar plate. Each stethoscope was cultured before and after cleaning with one of the two agents. Overall, 49 stethoscopes were cleaned with EBC and 50 stethoscopes were cleaned with IPA. Between platings, every participant cleaned his/her hands using two metered aliquots of EBC foam from an automatic wall dispenser. For EBC testing, participants rubbed their hands with EBC and then rubbed the entire stethoscope diaphragm between their hands. For IPA testing, participants rubbed their hands with EBC and then wiped the diaphragm in a circular pattern five times using an IPA pad. All stethoscopes were air-dried for 60 seconds after cleaning.
At baseline, every stethoscope grew bacteria prior to cleaning. The predominant bacteria seen in the cultures were gram-positive bacilli (80%), non-aureus Staphylococcus (75%), methicillin-sensitive S. aureus (3%), and group A Streptococcus (1%). No stethoscope grew methicillin-resistant S. aureus (MRSA) at baseline.
After cleaning, 28% of the stethoscopes were completely sterile. Of the remaining culture-positive stethoscopes, 81% grew gram-positive bacilli and 19% grew non-aureus Staphylococcus. There were no statistical differences in bacterial counts between the two cleaning agents (p = 0.25). Both agents dramatically reduced the number of colony-forming units on the agar plates by 93%, when compared with baseline (p < 0.0001). Neither agent was statistically superior to the other.
Nosocomial infections claim nearly 100,000 U.S. patient lives annually. In fact, the CDC estimates that one in 20 hospital admissions is complicated by a health care-associated infection (HAI).1 Like hand hygiene, stethoscope hygiene should be viewed as an essential component of reducing these infections. Indeed, the stethoscope is merely an appendage of the provider.
I like this study because it is simple but clinically relevant. The baseline contamination rate of 80% for stethoscopes is consistent with numerous studies dating back to the 1990s. Those older studies also revealed a high load of Staphylococcus species on stethoscopes. Given such knowledge, it seems ridiculous for providers to "foam-in, foam-out" of patient rooms, but then toss a contaminated stethoscope around their neck or into their coat pocket.
I believe stethoscope hygiene should be viewed as an integral component of hand hygiene. This study shows that using a foam-based EBC is just as effective as wiping with an IPA pad. The additional time required is minimal. Hopefully, this convenience factor will encourage providers to cleanse their stethoscopes more regularly.
Despite the focus of this article, hand and stethoscope hygiene is only the tip of the HAI iceberg. Studies have shown potentially high rates of bacteria on numerous objects, including neckties, white coats, nurse uniforms, writing instruments, computer keyboards, wash basins, and nametags. I must confess I often worry about the bacterial load in my own coat pocket where I carry my stethoscope. Within a few days of working in our ICU, I can only imagine the frightening cross section of bacteria that might be lurking in there. This study should encourage each of us to clean our stethoscope both before and after patient care, just like our hands.
1. Klevens RM, et al. Estimating health care-associated infections and deaths in US hospitals, 2002. Public Health Reports 2007;122:160-166. Available at: www.cdc.gov/ncidod/dhqp/pdf/hicpac/infections_deaths.pdf. Accessed July 1, 2009.