Steps Into STERI - STEP 3 - STERILISATION

The procedures required to prepare a contaminated reusable device ready for its intended use involve several steps. Known as instrument reprocessing, these steps follow an orderly flow from cleaning through to sterilisation and storage.

In our ‘Steps into Steri’ series, we have discussed Step 1 - receiving, cleaning, and decontamination, and Step 2 – Preparation and Packaging. Now we are ready for Step 3 - Sterilisation. At this stage, our instruments are clean, dry, packaged, and ready for the steriliser.

Steam sterilisation, also known as autoclaving, is a widely used and reliable method to render an item free of all forms of viable microorganisms. Steam is used, as it enhances the ability of heat and reduces the time and temperature required to denature or coagulate proteins in the microorganisms. For this to happen, steam sterilisation relies on four parameters - steam, pressure, temperature, and time. These parameters can be adjusted to sterilise different types of loads.

B-Class Sterilisers are recognised as being able to achieve sterility with various styles of solid or hollow instruments. Sterilisation of hollow items, such as handpieces and triplex syringes, requires special attention to ensure that the steam can penetrate and reach all surfaces of the device, including the narrow lumens.

Before the first active load is processed for the day, the four parameters must be tested to ensure that sterilisation has been achieved.

A Vacuum Leak Test (VT) is performed to ensure that the chamber is properly sealed and that no leaks are present. This test will show the integrity of the door seal for example. A high leak rate could mean that the door seal is damaged and may need replacing.

The vacuum leak test is run every day unless your steriliser incorporates an automatic air leak detection function, then it is performed weekly.

Air Removal and Steam Penetration Tests must be performed daily on vacuum-assisted steam sterilisers. A process challenge device (PCD), also known as a Helix Test, verifies that the steriliser has effectively removed all the air from the chamber, therefore allowing steam to penetrate all surfaces of the items being sterilised.

If any air remains it can create pockets where steam cannot reach. If any part of the item is not exposed to steam, it can lead to incomplete sterilisation. Daily testing identifies any issues before they become major problems.

In loads that contain porous items, air removal and steam penetration become more challenging. Porous loads, such as textiles, contain air pockets that can prevent steam from effectively penetrating the load. A Bowie-Dick-type testing device provides the challenge required to assess the air removal and steam penetration that is necessary for porous loads.

LOADING

A steam steriliser can only work effectively if steam can circulate freely and touch every surface of every instrument. Crowded, densely packed items touching each other, will inhibit steam penetration and sterility of those items. Load the items into the chamber in a way that ensures that they are evenly spaced and that there is adequate room for steam to circulate around them. When loading instruments that are not in pouches or wrap, a chemical indicator must be placed in each loading tray to be processed as a visual check that the items have been sterilised.

DRYING

At the end of the steam sterilisation process, items should be dry. Wet packs and wicking can create an environment in which bacteria can grow, and this can lead to the contamination of sterilised items. There is also a chance of instruments corroding, and puncturing or tearing of packs when they are still wet. In a steam steriliser that does not have a drying cycle, only unwrapped items may be processed.

When unloading the chamber, visually inspect each package. Look for any instruments that may have penetrated through the packaging, or seals on pouches that may have failed. Make sure the package is dry and that all chemical indicators’ have changed colour, as this shows that the required parameters have been achieved. Trays of instruments and wrapped items removed from the steriliser should be placed on racks and not directly on the bench to allow air to circulate. This prevents water condensation from occurring either around or inside the cooling packages.

VALIDATION

There are various qualification tests to ensure that the steam steriliser is installed properly, operates correctly, and can consistently achieve the required sterilisation conditions. Below is a brief explanation of each of the qualification tests for steam sterilisers:

Installation Qualification (IQ): ensures that the steriliser is installed properly according to the manufacturer’s specifications. It includes verifying that the steriliser is placed in the correct location, that all necessary utilities are properly connected, and that the required documentation is in place.

Operational Qualification (OQ): This includes testing that all the controls and sensors are working correctly, that the cycle parameters are within the specified range, and that the steriliser can consistently achieve the required sterilisation conditions.

Performance Qualification (PQ): This qualification evaluates the overall performance of the steriliser under realistic conditions. The prerequisites for PQ are successful IQ and OQ tests. It includes testing with challenging loads that represent the range of items to be sterilised, to ensure sterilisation of all types of loads. It also includes monitoring the process to ensure that it is consistent, and that the steriliser is performing within the required parameters.

The 3M™ Attest™ Mini Auto-reader with biological indicators (spore tests) provide sterilisation monitoring results in just 24 minutes. Record the testing results in a validation log in your policy and procedure manual. If the results do not meet the established protocol, corrective actions should be taken, and the process should be revalidated.