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Decontamination of medical equipment


Healthcare-associated infections are the leading cause of preventable disease. In the United Kingdom, they are responsible for more than 5000 deaths per year and cost the National Health Service over £1billion every year. Failure to adequately decontaminate equipment carries not only the risk associated with breach of the host barriers but the additional risk of person-to-person transmission (e.g. hepatitis B virus) and transmission of environmental pathogens. Decontamination is a term encompassing all the processes necessary to enable a reusable device to be reused. This includes cleaning, disinfecting, inspecting, packaging, sterilizing, transporting, storing and using ( Table AppC.1 ). The decontamination process is required to make medical devices:

  • 1.

    safe for users to handle and

  • 2.

    safe for use on the patient.

Table AppC.1
Cleaning, disinfection and sterilization
Cleaning Disinfection Sterilization

  • Cleaning is the removal of visible soil (e.g. organic and inorganic material) from objects and surfaces.

  • It is normally accomplished by manual or mechanical means using water with detergents or enzymatic products.

  • Cleaning does much to reduce risk of vCJD.

  • Disinfection describes a process that eliminates many or all pathogenic microorganisms on inanimate objects with the exception of bacterial spores.

  • It is usually accomplished by the use of liquid chemical and heat (washer disinfector).

  • Sterilization is the complete elimination or destruction of all forms of microbial life. This is accomplished in healthcare facilities by either physical or chemical processes.

vCJD , Variant Creutzfeldt-Jakob disease.

Clean, disinfect or sterilize instruments?

As there is no need to sterilize all clinical items and some items cannot be sterilized, healthcare policies must identify whether cleaning, disinfecting or sterilizating is indicated based primarily on the items’ intended use.

Earle H. Spaulding devised a classification system where instruments and items used for patient care are divided into three categories based on the degree of risk of infection involved in the use of the items ( Table AppC.2 ).

Table AppC.2
Spaulding classification
Critical Semicritical Noncritical

  • Items which enter normally sterile tissue or the vascular system or through which blood flows.

  • They have a high risk of infection.

  • These items should be sterile.

  • Examples: surgical instruments and needles.

  • Items that touch the mucous membranes or skin that is not intact.

  • They require a high-level disinfection process, i.e. mycobactericidal.

  • As intact mucous membranes are generally resistant to infection, such items pose an intermediate risk.

  • Such devices should ideally be sterilized, but chemical disinfection is usually reserved for those that are intolerant of heat sterilization.

  • Example: laryngoscopes.

  • Items that touch only intact skin require low-level disinfection.

  • As skin is an effective barrier to microorganisms, such items pose a low risk of infection.

  • Examples: bedpans and blood pressure cuffs.

This classification has been successfully used by infection control professionals and others when planning methods for disinfection or sterilization.

The ease of inactivation differs according to the microorganisms involved ( Fig. AppC.1 ).

Fig. AppC.1, Descending order of resistance of microorganisms against inactivation.

Cleaning

Involves physical removal of the infectious material or organic matter on which microorganisms thrive. The critical parameters for cleaning are the following:

  • 1.

    Temperature: initial wash temperatures must be below 45°C to prevent coagulation of tissue/blood residues.

  • 2.

    Chemicals: detergents used are a complex formulation of chemicals designed to remove soil (proteins, carbohydrates, lipids, etc.) from instruments. Detergents have an optimal concentration and pH to work effectively.

  • 3.

    Energy: may take the form of manual washing, ultrasonic energy or water jets/sprays in automated washer disinfectors.

  • 4.

    Time: cleaning cycle requires a suitable time period to achieve its desired effect.

Cleaning can be achieved either by:

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