ABSTRACT: Stainless steel surgical instruments are found in every veterinary practice, and can add up to a major investment. A good instrument care protocol, which everyone understands and follows, will maintain the instruments in good working order and prolong their useful life. The purpose of this article is to explain the necessary steps in this protocol and why they should be followed. And what can happen if they are not!

One of the largest investments in veterinary practice – and one which is used continually – is the surgical instrument set-up. This will comprise a range of equipment, the make-up of which will depend on the surgical caseload of the particular clinic.

Every practice will have basic soft tissue instruments; most will have some orthopaedic basics, along with more general surgical instruments, such as abdominal retractors. At the other end of the spectrum, the large referral hospitals will require a wide range of instruments covering multiple specialities.

Dental instruments should also be regarded and treated as surgical instruments, requiring the same level of care to maintain optimum performance.

Stainless steel

The majority of multi-patient autoclavable surgical instruments are made of stainless steel. There are many different types of stainless steel alloys, containing varying amounts of nickel and chromium to increase resistance to corrosion.1 All types of stainless steel will corrode under certain conditions – so the term ‘stainless’ is a little misleading.

The proportions of the various constituents will affect the characteristics of the final steel, particularly its resistance to corrosion and ability to take and keep an edge, along with the degree of hardening applied.1

Steel instruments are raised to very high temperatures and cooled during the hardening phase of the manufacturing process. This increases the strength and resistance to bending of the steel, but at the same time makes it more brittle.

Surgical instruments, such as scissors, must be hard enough to take and keep a cutting edge; or must have a degree of flexibility, for example, artery forceps. The steel possessing these qualities contains less chromium and more carbon than orthopaedic implants.

Implants are made of steel with the primary characteristic of resistance to corrosion, which makes it too soft for instruments. The penalty is that this type of higher carbon stainless steel (called Martensitic) has a reduced resistance to corrosion and staining compared to some other stainless steels. However, correctly cared for, it will give many years of service.

Steel for surgical instruments is specified to BSEN1SO 7153-1:2001. 2 The parts of the steel likely to rust are protected by a thin layer of chromium oxide which is produced by the chromium part of the steel during a process called self passivation. Actions which encourage the production of chromium oxide minimise corrosion. Actions which either physically or chemically destroy this layer of chromium oxide encourage rusting or staining.2-3

Maximising the chromium oxide layer is the basis of sound instrument care.

This layer thickens with age and increases the resistance of your instruments to corrosion – in new instruments it is relatively thin. This is why you may have marking problems with new instruments (or repaired/re-polished ones) but your old ones are fine – new instruments will be more intolerant of inappropriate detergents, inadequate lubrication and the corrosive environment of the autoclave.3

Basics of instrument care

To keep your instruments in peak condition, there are some basic rules which should be followed:

•  Handle your instruments with care – abuse such as dropping and scratching will all damage the surface of instruments and reduce their resistance to corrosion.

•  Store with care – if instruments are stored damp, they will corrode. This includes in bags or boxes which have come out of the autoclave, damp. Equipment that is not used on a regular basis is better stored clean, dry and lubricated ready for sterilisation before use. Delicate instruments should be packed with protective tips and silicone storage box inserts (Figure 1) or in suitable racks to stop them rattling around. Always make sure heavy instruments are not stored on top of lighter equipment.

Figure 1: Autoclavable silicone-fingered box and silicone-tipped protectors

•  Use them to do what they were designed for! Artery forceps are not needle-holders or wire twisters, bone cutters are not designed to cut wire, and implant cutters have a size rating for a reason! Inappropriate use will damage instruments and invalidate warranties – and cost money to replace! 

•  Avoid mixing different metals when processing instruments – keep chrome-plated, industrial finish and aluminium items separate from stainless steel, particularly in ultrasonic cleaners.3

The basic decontamination cycle for surgical instruments is shown in Figure 2. Each stage of this should be followed for best results.

Figure 2: Autoclavable silicone-fingered box and silicone-tipped protectors

Cleaning of instruments

Manual cleaning of instruments requires minimal equipment. A basic protocol is shown in Table 1.

A range of suitable brushes is useful. These should be soft nylon for most instruments, and include fine tube brushes for instruments with a lumen, such as drill guides. Pipe-cleaners can. also be useful.

For drills, reamers and spinal burs, stainless brushes can be used. These should only be of fine stainless wire and be specifically supplied for instrument cleaning.4 Rasps may require a heavier duty brush, sometimes listed as ‘orthopaedic’ in catalogues.4 Most instrument suppliers list a range of suitable brushes. Heavy duty domestic or industrial wire brushes shou
ld not be used as they will destroy the surface of the instrument, resulting in increased corrosion.

Instrument cleaning solutions must be used at the correct dilution and duration of contact as specified by the manufacturers. Suitable products include Rapidex and Rapizyme (Rapidex), Medizyme (Medichem International) but there are many others to choose from. These are low-foaming enzyme-based products, which can also be used in ultrasonic units and they efficiently remove organic residues prior to sterilisation.

Make sure the solution you use is correct for the metal you are cleaning. Using a stainless steel stain remover on plated items will strip the plating (Figure 3).

Figure 3: Coating stripped from drill bit by acid stainless steel surface stain remover

Ultrasonic instrument cleaners are very useful in an instrument care protocol.3 These will allow thorough cleaning of areas which are otherwise impossible to reach with brushes, such as the lumen of fine instruments and the inner surfaces of box joints. This will remove build-up within joints, which causes stiffening over time (Figure 4). They are also the most efficient way to clean burrs and reamers, and they do not damage the cutting edges.

Figure 4: Long-term biological debris build-up within joint. End result – instrument failure!

Instrument washer/disinfector units, which are the norm in human instrument reprocessing, are now becoming available in the veterinary market. New guidelines for dental practices also recommend use of these as best practice.5

These machines are designed to clean instruments thoroughly, and usually have lumen flushing attachments for dental hand-pieces and similar instruments. They also incorporate a thermal disinfection stage during which the load is held at 90°C for one minute. Washer- disinfectors allow for documentation and validation of cycles.

If you make the decision to go down this route, select a machine which is compliant with HTM 01-05 and EN ISO 15883 as a minimum. Cleaning and sterilising guidelines in human healthcare are covered in HTM 2030, HTM 2010 and BS EN ISO 17665-1.

Visual checking and lubrication

Once cleaned, instruments are ready for lubrication. Always carry out a visual check at this stage – are the cutting edges of scissors free of damage, do the jaws of artery forceps and needle-holders meet correctly with no signs of twisting, for example? Check that all thumbscrews are tight in instruments, such as Gelpi retractors and stifle distractor joints.

Check for fine cracks in instruments, for example, across the box joints in artery forceps. Leave all joints and ratchets open for lubrication and sterilisation, as this will allow steam and lubricant to access all surfaces and prevent strain on joints caused by heat expansion in the autoclave, if the instrument is under tension.

Damaged items should either be disposed of or be sent for repair. Items being sent for repair must be decontaminated by cleaning thoroughly and then sterilised. If necessary, these items can be marked using plastic tags prior to processing, so they do not inadvertently go back into the normal instrument kit.

Repairers usually require a certificate of decontamination to be sent with instruments, and instruments should never be sent out in a soiled condition.

Lubrication should not be forgotten – either an ‘instrument milk’ bath such as Eezee-lube (Medisave) or an instrument oil (Instol instrument lubricant spray, Aesculap Sterilit instrument oil and spray). This is an essential – and often overlooked – part of the care cycle.

There are many materials available for packing instruments for autoclaving. Paper peel-packs are commonly used, along with nylon autoclave film. Laundered fabrics used as instrument wraps can cause problems, because residual detergents and bleaches can cause pH- and chloride-related damage to the instruments. Disposable non¬woven autoclavable instrument wrapping material similar to disposable drapes are available.

Make sure the packaging you use is suitable for your autoclave, and use appropriate indicators to monitor the process. Fabric-wrapped packs in a non vacuum autoclave may result in poor steam penetration, so monitor the process very carefully.

The autoclave is a very hostile environment for your instruments. The combination of heat and moisture promotes corrosion and staining, particularly if there are residual detergents in wrapping materials. This is also true where tap water, instead of distilled or demineralised water, is used in the autoclave.

Mineral deposits on instruments are unsightly and can interfere with normal joint function. They are difficult to remove, so prevention is better than cure. Chloride ions from water treatments and laundry detergents, as well as those from organic contaminants, can build up and damage the surface of the instrument, causing pitting.

Rust and contaminants in the steam pipes of your autoclave will transfer to your instruments, so autoclave maintenance is important. Regular servicing ensures the autoclave is working correctly. Vacuum autoclaves help remove residual steam from packs but it is important that directions are followed and cycles are completed.

Regularly check that the door seal is undamaged, and replace it if necessary. Drain and refill the water tank regularly with distilled water, unless your machine does this automatically. You may well be surprised what comes out!

If your packs are coming out of the autoclave wet, then there is a cycle problem and you need to speak to your autoclave engineer for advice. Wet storage will result in corrosion and damage to your instruments.

So – store your instruments clean, dry, lubricated and protected and they will give you many years of service. A good, easy-to-follow instrument-care protocol will extend instrument life, save money and result in happy surgeons! 

Author

Linda Capewell VN

Linda qualified in 1988 after 10 years in practice with the PDSA in Sheffield, as one of the first group of the charity's VNs. She spent a total of 26 years with the PDSA, and then in 2004 she left and joined Veterinary Instrumentation as veterinary technical support manager. She now deals with a wide range of queries every day.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.00173.x or Veterinary Nursing Journal Vol 27 pp 173-176

References

1.   British Stainless Steel Association. How many types of stainless steel are there? http://www.bssa.org.uk/faq.php?id=10 Accessed February 2012

2.   British Stainless Steel Association. Selection of stainless steel for surgical instruments http://www bssa.org uk/topics php?article=132 Accessed February 2012

3.&
nbsp;  Instrument Preparation Working Group. Proper Maintenance of Instruments in Veterinary surgeries. Germany 2006. http://www a-k- i.org/index.php?id=13&L=1

4.   Veterinary Instrumentation. Current catalogue. Sheffield

5.   Department of Health. Decontamination – Health Technical Memorandum 01-05: Decontamination in primary care dental practices London 2009

Further reading

Department of Health NHS Estates. A guide to the decontamination of reusable surgical instruments 2003. http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_4120907.pdf

Surgical instrument care sheets – many online manufacturer references [See reference 5 above]

• VOL 27 • May 2012 • Veterinary Nursing Journal