Simethicone is retained in endoscopes despite reprocessing: impact of its use on working channel fluid retention and adenosine triphosphate bioluminescence values (with video)

Abstract

Background and aims: Studies from our group and others demonstrate residual fluid in 42% to 95% of endoscope working channels despite high-level disinfection and drying. Additionally, persistent simethicone has been reported in endoscope channels despite reprocessing.

Methods: Endoscopy was performed by using water or varied simethicone concentrations (0.5%, 1%, 3%) for flushing. After high-level disinfection/drying, we inspected endoscope working channels for retained fluid by using the SteriCam borescope. Working channel rinsates were evaluated for adenosine triphosphate (ATP) bioluminescence. Fourier transform infrared spectroscopy was performed on fluid droplets gathered from a colonoscope in which low-concentration simethicone was used.

Results: Use of medium/high concentrations of simethicone resulted in a higher mean number of fluid droplets (13.5/17.3 droplets, respectively) and ATP bioluminescence values (20.6/23 relative light units [RLUs], respectively) compared with that of procedures using only water (6.3 droplets/10.9 RLUs; P < .001). Two automated endoscope reprocessing cycles resulted in return of a fluid droplet and ATP bioluminescence values to ranges similar to that of procedures that used only water (P = .56). Low-concentration simethicone did not increase the mean residual fluid or ATP bioluminescence values compared with procedures that used only water (5.8 droplets/15.6 RLUs). Fourier transform infrared analysis revealed simethicone in the endoscope working channel after use of low-concentration simethicone.

Conclusions: Use of medium/high concentrations of simethicone is associated with retention of increased fluid droplets and higher ATP bioluminescence values in endoscope working channels, compared with endoscopes in which water or low concentration simethicone was used. However, simethicone is detectable in endoscopes despite reprocessing, even when it is utilized in low concentrations. Our data suggest that when simethicone is used, it should be used in the lowest concentration possible. Facilities may consider 2 automated endoscope reprocessor cycles for reprocessing of endoscopes when simethicone has been used.

Figure 1.

A, Borescope examination demonstrating a large, shallow, opaque pool of fluid immediately after injection of 3% simethicone suspension into the colonoscope working channel. B, Relatively clear fluid droplets after manual cleaning/HLD/drying. C, Relatively opalescent fluid droplets after manual cleaning/HLD/drying.

Figure 2.

A, Fourier transform infrared analysis of residual working channel fluid droplets despite HLD/drying after use of low-concentration simethicone. B, Comparison of the working channel fluid droplets with a commercial standard reference simethicone sample confirming spectra.

Figure 3.

Intermittent blurring of the endoscopic image after use of 3% simethicone. Endoscopic appearance of rectal mucosa when initially affected by blurring (far left) and after 5, 10, and 15 seconds of washing by using the lens water jet apparatus.

Figure 4.

A, Boxplot representation of residual fluid droplet abundance (number of droplets) after use of water and low, medium, and high concentrations of simethicone. B, Boxplot representation of fluid droplet abundance for water/low concentration simethicone and medium/high concentration simethicone flushes. Boxes represent interquartile ranges. Whiskers represent the lowsest or highest data point still within a 1.5 multiple of the interquartile range.

Figure 5.

A, Boxplot representation of adenosine triphosphate (ATP) bioluminescence values in Relative Light Units (RLU) after use of water and low, medium, and high concentrations of simethicone. B, Boxplot representation of ATP bioluminescence values for water/low concentration simethicone and medium/high concentration simethicone. Boxes represent interquartile range. Whiskers represent the lowest or highest data point still within a 1.5 multiple of the interquartile range.