Introduction

The lifetime of an instrument can be prolonged if used properly and cared for well. With the money practices have to spend on equipment being reduced over the last year or so this has become even more important. To help prevent damage each instrument should only be used for its intended design. Although this may not be the direct responsibility of the veterinary nurse gentle persuasion may be necessary!! A damaged instrument may cause problems especially in the emergency situation; a clamp that does not meet may prove to have dire consequences.

This lecture and notes cover care and sterilisation of basic instrumentation. Speciality instruments may require different methods of care. As with all new instruments guidelines produced by the manufacturers should be consulted prior to use.

Perioperatively it is important that the surgical assistant keeps instruments free from blood, usually with a saline-soaked swab, to prevent contamination of the surgical site and damage of the instruments (it is preferable to use sterile distilled water to keep instruments clean on the table but the availability of this is limited and so sterile saline is often used perioperatively).

At the end of the surgical procedure all sharps must be dealt with correctly. Postoperatively the instruments should be rinsed under running water, warm but not hot, to remove gross contamination and debris. All instruments should be opened to allow debris to be removed from hinges and box joints. If cleaning is not possible immediately then the instruments should be submerged in a solution of water and a neutral pH detergent. Alternatively a wet towel can be put on top of them to prevent them drying out. Soaking instruments in saline solution is not recommended as it can result in corrosion, which can eventually lead to pitting of the stainless steel. This pitting can cause debris to become entrapped, interfere with the sterilisation process and result in the instrument being damaged beyond repair. If blood dries out on instruments, even stainless steel, then staining can lead to rusting that can ruin that instrument forever.

Once gross contamination has been removed there are then a number of methods of cleaning that must occur: manual cleaning, ultrasonic cleaning and mechanical cleaning.

Manual Cleaning

When manually washing instruments they should be washed individually beneath the surface of the water to prevent aerosol and splashing of any debris. This method of cleaning is probably most used for small delicate instruments that may be easily damaged in a mechanical washer/disinfector.

Ultrasonic Cleaning

This should only be used after all gross contamination has been removed. Ultrasonic cleaners use a process called cavitation to remove debris that was not removed during the manual cleaning process. High-frequency sound waves, ultrasonic energy, generate tiny bubbles in the solution. The bubbles expand until they collapse and it is this implosion that generates a tiny vacuum that dislodges and dissolves any debris or contamination. This method is very useful as the bubbles are small enough to enter the hinges, serrations and box joints of instruments that cannot be reached during manual washing.

Mechanical Cleaning

A washer-decontaminator/disinfector is now becoming more commonplace in the veterinary hospital. In the human hospital environment this method of cleaning instruments has many benefits including reducing the risk of exposure of personnel to contaminants. There is a variety of cycles including cool-water rinse, enzyme soaking, washing, sonication (ultrasonic cleaning), hot-water rinse, germicide rinse and drying. Deionised or softened water is used at least in the rinsing phase to prevent detergent residues this means they do not require lubrication and prevents damage to the instrument. Instruments are placed in wire mesh baskets with their joints open to allow a greater surface area of cleaning.

Lubrication

If the instruments have undergone manual and/or ultrasonic cleaning they must be lubricated prior to sterilisation. Lubricants must be water soluble to allow steam penetration during sterilisation as oily solutions cannot be penetrated.

Sterilisation

Once clean the instruments must be dried fully before being sterilised, and this is often a suitable time to inspect them fully before being packed. Instruments should be inspected for cleanliness, proper function, alignment, defects, sharpness of cutting edges, looseness of pins and chipping of plated surfaces. Any instruments that are in poor working condition should be removed from circulation as they pose a risk to patients.

Sterilisation can only occur if the sterilisation agent comes into contact with all surfaces of every instrument. Most instruments are made of stainless steel and can be sterilised by steam under pressure. Other items that are heat or moisture sensitive will require the use of other methods such as ethylene oxide or hydrogen peroxide gas plasma. Items can be packed in individual pouches or in groups in trays.

Monitoring the Sterilisation Process

The sterilisation process must be monitored to ensure that it is effective. All personnel should be trained and confident in safe practices when using all methods of sterilisation. Mechanical, chemical and biological indicators should also be used; however, these have their own limitations.

Mechanical indicators, especially on large autoclaves and other machinery, can indicate a failed cycle and record charts are also produced. Chemical indicators that change colour to verify exposure to a sterilisation process are commonplace and there are several types available including autoclave tape and special markings on sterilisation pouches and bags. These indicators demonstrate only that an item has been processed through a steriliser (i.e., the item has been exposed to a certain temperature for some unknown length of time), not that sterilisation has been successful.

Sterilisation is designed to kill all microbes. Unfortunately it is impossible to test whether all microbes have been killed and so demonstrating the death of bacterial spores is used as the main guarantee of sterilisation. Biological indicators contain bacterial spores for monitoring and are available in a number of ways. Spore strips, one-inch paper strips that are enclosed in a protective glass envelope, and self-contained vials, with a spore strip within an ampoule filled with growth medium, are two methods. After processing through the steriliser, the strips are incubated in a tube of appropriate broth medium. If live bacterial spores still are present, they will grow and produce cloudiness and/or change the colour of the growth medium, indicating sterilisation failure.

Both of these methods do not give results of sterility for a period of time after the cycle, sometimes days. In veterinary practice this may be impractical as the number of kits available is limited compared to in a human hospital.

Once removed from the sterilising process the expiry date must be stamped on the packet. Care must be taken when storing instruments to prevent damage to the packages. Some hospitals adopt an 'indefinitely sterile' policy for items that are double wrapped with a sealed dust cover and whilst fully intact; most store items for approximately 6–12 months.