Introduction

All staff involved with anaesthetic equipment have a duty of care to ensure that the risk of hospital-acquired infection from anaesthetic equipment is kept to an absolute minimum. To this end in the UK, guidelines on infection control in anaesthesia were first published by the Association of Anaesthetists of Great Britain and Ireland (AAGBI) in 2002 and updated in 2008.¹ Also in the UK, healthcare organizations now have a legal responsibility to implement changes to reduce healthcare-associated infections (HCAIs). The Health Act 2006² provided the Healthcare Commission with statutory powers to enforce compliance with the Code of Practice for the Prevention and Control of Healthcare Associated Infection.

Although there are only a limited number of published reports relating to cross-infection,^3,4 the AAGBI recommendation was that all reusable anaesthetic equipment must be appropriately decontaminated prior to patient use and single-use items must be discarded immediately following use. Unfortunately, wide variation in decontamination practices between anaesthetic departments is well recognized. This can be avoided by ensuring that every hospital has a comprehensive infection control policy in place for all anaesthetic equipment, with a nominated anaesthetist and infection control doctor (ICD) taking lead responsibilities.⁵ Such a policy should be evidenced-based and subject to periodic audit and review. Other useful UK web-based resources include the National Resource for Infection Control and the NHS Library (Surgery, Theatres and Anaesthesia Specialist Library). Key areas requiring risk assessment are listed in Table 21.1.

The aim of this chapter is not to be prescriptive, but to provide the necessary background information for a hospital to formulate its own anaesthetic equipment infection control policy in order to minimize the risk of HCAIs and comply with the UK’s ‘Health Act 2006’.²

Risk assessment and the decontamination process

Contaminated medical devices are typically classified into three infection risk categories:⁶

If disposable anaesthetic equipment is chosen (Fig. 21.1), then a risk assessment may not be required. However, it is important to remember that disposable equipment will be for ‘single use’ or ‘single patient use’ only. ‘Single use’ indicates that the manufacturer intends the item to be used once only on an individual patient and then discarded. The packaging will be labelled either ‘Single use’, ‘Do not re-use’ or with the symbol .

Figure 21.1 A selection of single-use anaesthetic equipment.

’Single patient use’ indicates that the manufacturer advises that the item may be used more than once on the same patient.⁷ Examples of ‘single patient use’ items in anaesthesia include ventilator tubing and bacterial/viral filters used in critical care units.

By its nature, reusable anaesthetic equipment poses an intermediate or high (if used on broken mucous membranes or skin) risk of infection. Consequently, decontamination by sterilization or disinfection is required. However, the responsibility for choosing the correct decontamination method lies with the sterile services department (SSD) manager, supported by the ICD, the lead clinician and the relevant manufacturer’s guidance. This is because the choice of decontamination method will depend on a number of factors, including the nature of the contamination, the time required for processing, the heat, pressure, moisture and chemical tolerance of the item, the availability of the processing equipment and the risks associated with the decontamination method. Furthermore, decontamination performed in SSDs will ensure that procedures are undertaken in a controlled and standardized manner, as well as being subject to audit review. Consequently, detailed knowledge of decontamination processes is not required by users. However, a sound understanding of the principles and level of decontamination required is essential, to ensure that a local infection control policy is both practical and supported by all staff involved in intensive care and anaesthetic practice. This also applies to the purchase or loan of any new anaesthetic equipment, since a preliminary decontamination assessment must be made prior to its use on patients.

Terminology

Decontamination

This refers to the removal or destruction of contaminants (soiling with potentially infectious or other unwanted material). Decontamination involves either cleaning alone, cleaning followed by high-level disinfection or cleaning followed by sterilization.

Bioburden

This is the population of viable infectious agents contaminating a medical device and should be routinely assessed by SSDs.

Cleaning

This is the physical removal of infectious agents or organic matter. It involves washing with a solvent (usually water and detergent), which may be heated (e.g. thermal washer disinfection, Fig. 21.2). This process does not necessarily destroy infectious agents. It is an essential process prior to disinfection or sterilization to remove bioburden. Items may also be placed in a water bath incorporating an ultrasound generator (Fig. 21.3). The ultrasound causes the water to vibrate at high frequencies so that it literally ‘shakes’ off organic matter. Ultrasonic washers are particularly useful for equipment where conventional cleaning methods might not reach some aspects of the device, or where items are too delicate to be physically scrubbed (e.g. some ophthalmic instruments).

Figure 21.2 Laryngeal masks going into washer-disinfector.

Figure 21.3 Ultrasonic washer used for endoscope accessories.

Disinfection

This process reduces the number of viable infectious agents, but does not inactivate all microbial agents or bacterial spores. Low-level disinfection kills most vegetative bacteria (except mycobacteria and endospores), some fungi and some viruses. High-level disinfection kills vegetative bacteria (but not endospores), mycobacteria, fungi and viruses.

Sterilization

This is a validated process used to render a device free from infectious agents, including viruses and bacterial spores. Prions, which are recognized to cause transmissible spongiform encephalopathies (TSEs), are resistant to inactivation by conventional disinfection methods and sterilization procedures.

Sterilant

This is a liquid chemical agent, which can kill bacteria, fungi, viruses and bacterial spores (e.g. gluteraldehyde, chlorine dioxide, peracetic acid). However, this term is not precise and is not generally used. The term high-level disinfectant is preferred. A flow chart of appropriate decontamination methods is shown in Fig. 21.4.

Figure 21.4 The decontamination process.⁶

Dry saturated steam

This involves saturated steam that contains no water particles in suspension (Fig. 21.5). See also Fig. 21.4.

Figure 21.5 Autoclave in sterile services department.

Infection control strategies