How correct ultrasound disinfection procedures protect patients

Correct disinfection of re-usable medical devices, including ultrasound probes, is important to prevent infection transmission. The number of ultrasound procedures is rapidly increasing and the need to keep up to date on reprocessing requirements may be challenging for some ultrasound users.

In Australia, ultrasound is increasingly utilised as an imaging modality across a broad range of healthcare departments/specialties. Many of these probes may be used on intact skin, non-intact skin or mucous membranes, or could even occasionally contact sterile tissue. This presents a complex challenge, as contact with these various body sites necessitates differing levels of disinfection (eg, low-level disinfection or high-level disinfection) prior to the probe’s use.

Procedures are now taking place in different hospital inpatient and outpatient departments by health professions who include sonographers, physicians, nurses, anaesthetists, interventional radiologists, OBGYNs, nurse practitioners and physician assistants. This has resulted in an increased use of surface probes for semi-critical and critical procedures such as biopsies, cell retrieval, cannulation, catheterisation, injections, ablations, surgical, aspirations and drainages.

Risks

Recent publications have highlighted the risk of using ultrasound if proper disinfection procedures are not followed.

In 2012, a patient died from a hepatitis B infection which was likely to have been caused by a failure to appropriately decontaminate a transoesophageal echocardiography probe between each patient use. As result of this fatality, a Medical Device Alert was issued advising users to appropriately decontaminate all types of re-usable ultrasound probes.¹

Furthermore, according to a 2017 study carried out by National Health Services Scotland, patients were 41% more likely to receive positive bacterial cultures after a transvaginal scan when probes were only low-level disinfected.²

Users should not only be concerned about correct probe disinfection, but also probe handle disinfection, as a study found that probe handles are not routinely disinfected and 80% were found to be contaminated.³

Another important point for consideration is that while many sonographers believe that their transvaginal ultrasound patients are protected from infection risk by using barrier shields and/or condoms, research has shown that up to 9% leak.^4–7 Australian guidelines require that these probes undergo high-level disinfection (HLD) even when a sheath is used.⁸

Correct reprocessing

The diverse use of ultrasound probes is now prompting a renewed focus on correct probe reprocessing to ensure patient safety.

The ACIPC-ASUM Guidelines on the reprocessing of ultrasound transducers (released February 2017) follow Australian and New Zealand standards (AS/NZS 4187:2014 and AS/NZS4815:2006). These guidelines are a world-first joint guideline between an infection prevention and ultrasound society and form the minimum recommended practice for reprocessing ultrasound transducers in Australia. They really highlight that to ensure best practice standards, infection preventionists and ultrasound users need to work together to reduce the risk of infection that is associated with using ultrasound probes.

It’s not just intracavity probes that require HLD

Guidelines from around the world, including those here in Australia, require ultrasound probes that come into contact with mucous membranes and non-intact, broken skin to be high-level disinfected.^{8–15, 17}

A number of guidelines even specifically outline that automated validated processes for ultrasound reprocessing are the preferred option. This is supported by a study relating to manual disinfection methods which found that only 1.4% were fully compliant when using manual methods, compared to 75.4% when using semi-automated disinfection methods.¹⁶

Spaulding Classification

The Spaulding Classification is a widely adopted disinfection framework for classifying medical devices based on the degree of infection transmission risk associated with their use.

It states that devices which only contact intact skin are considered ‘non-critical’, while devices that contact broken skin or mucous membranes are considered ‘semi-critical’. Furthermore, devices that contact or enter sterile tissue or the vascular system are considered ‘critical’. Corresponding levels of disinfection or sterilisation are then assigned, with non-critical devices requiring low-level disinfection, semi-critical devices requiring high-level disinfection and critical devices requiring sterilisation.¹⁷

It is important that the Spaulding Classification system is applied before a procedure commences so that information about what tissues or body sites may be contacted are taken into account. This ensures that a correctly disinfected or sterilised transducer can be selected for use to maximise patient safety.

Conclusion

Ultrasound users should work with their infection prevention colleagues to understand current Australian guidelines and standards for reprocessing ultrasound probes. While the expansion of ultrasound carries potential infection control challenges, proper education is key to maintaining patient safety and minimising the risk of infection.

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References

1. Medicines and Healthcare Products Regulatory Agency (UK). Medical Device Alert: Reusable transoesophageal echocardiography, transvaginal and transrectal ultrasound probes (transducers) (MDA/2012/037), 2012.
2. Health Protection Scotland, NHS National Services Scotland. NHSScotland Risk Based Recommendations for the Decontamination of Semi-Invasive Ultrasound Probes: Risk of infection following semi-invasive ultrasound procedures in Scotland, 2010 to 2016. Version 1.0. October 2017. Accessible at http://www.hps.scot.nhs.uk/pubs/detail.aspx?id=3366.
3. Ngu A et al. Reducing Transmission Risk Through High-Level Disinfection of Transvaginal Ultrasound Transducer Handles, Journal for Infection Control & Hospital Epidemiology, volume 36, May 2015.
4. Amis S et al. Assessment of condoms as probe covers for transvaginal sonography. J Clin Ultrasound 2000;28(6):295−8.
5. Milki A A and Fisch JD. Vaginal ultrasound probe cover leakage: implications for patient care. Fertil Steril 1998;69(3):409−11.
6. Storment J M et a l. Ineffectiveness of latex condoms in preventing contamination of the transvaginal ultrasound transducer head. South Med J 1 997;90(2):206−8.
7. Masood J et al. Condom perforation during transrectal ultrasound guided (TRUS) prostate biopsies: a potential infection risk. Int Urol Nephrol 2007;39(4):1121−4.
8. ACIPC-ASUM. Guidelines for Reprocessing Ultrasound Transducers. Australasian Journal of Ultrasound in Medicine. 2017;20(1):30-40.
9. Society and College of Radiographers (SCoR) and British Medical Ultrasound Society (BMUS). Guidelines For Professional Ultrasound Practice. Section 1.7: Transducer Cleaning and Disinfection. Revision 2, December 2017. Available at: https://www.bmus.org/static/uploads/resources/SCoR__BMUS_Guidelines_for_Professional_Ultrasound_Practice_Revised_Dec_2017_cG4AOnF.pdf.
10. Nyhsen CM, Humphreys H, Koerner RJ, Grenier N, Brady A, Sidhu P, et al. Infection prevention and control in ultrasound - best practice recommendations from the European Society of Radiology Ultrasound Working Group. Insights Imaging. 2017:doi: 10.1007/s13244-017-0580-3.
11. European Committee for Medical Ultrasound Safety (ECMUS). Best Practice recommendations for cleaning and disinfection of ultrasound transducers whilst maintaining transducer integrity.: 2017.
12. Health Facilities Scotland, NHS National Services Scotland, Health Protection Scotland. Scotland, March 2016. NHSScotland Guidance for Decontamination of Semi-Critical Ultrasound Probes; Semi-invasive and Non-invasive Ultrasound Probes. Document: HPS/HFS Version 1.0.
13. World Federation for Ultrasound in Medicine and Biology
14. Health Service Executive (HSE) Quality Improvement Division – Decontamination Safety Programme. Ireland, January 2017. HSE Guidance for Decontamination of Semi-critical Ultrasound Probes; Semi-invasive and Noninvasive Ultrasound Probes. Document: QPSD-GL-028-1.
15. Welsh Health Technical Memorandum WHTM 01-06. Wales, 2014. Decontamination of flexible endoscopes Part C: Operational management (Including guidance on non channelled endoscopes and ultrasound probes).
16. Ofstead, CL et al., Endoscope reprocessing methods: A prospective study on the impact of human factors and automation. Gastroenterology Nursing, 33:304–11, 2010.
17. Rutala WA, Weber DJ, Healthcare Infection Control Practices Advisory Committee (HICPAC), Centre for Disease Control and Prevention (CDC). Guideline for Disinfection and Sterilization in Healthcare Facilities. USA: Centers for Disease Control 2008.