Theatre practice

Before undertaking a surgical procedure, whether it is minor (e.g. blood sampling) or major (e.g. a bitch spay or an exploratory laparotomy), it is vital that you consider all the steps involved in aseptic preparation. Any technique that involves the breaching of the skin, which acts as the body’s primary barrier against the outside environment, must be carried out under sterile conditions. Even a simple injection risks the introduction of pathogens into the body, and when opening up a body cavity the risk of infection is far greater.

To ensure asepsis within the operating theatre, each surgical procedure should be classified according to the degree of infection (Table 9.1) and this should be taken into account when organizing the day’s operating list. To reduce the chances of breaking asepsis, always start with the clean procedures and progress through the operations, finishing with the dirty ones.

Table 9.1

Classification of surgical procedures

Classification	Types of procedure	Comment
Clean	Non-traumatic elective procedures; orthopaedic procedures with no connection to traumatic wounds; simple tumour removals	Gastrointestinal, respiratory and urinary tracts are not entered; asepsis maintained throughout; no acute inflammation
Clean-contaminated	Ovariohysterectomy and orchidectomy	Procedures in which the gastrointestinal, respiratory and urinary tracts are entered but there is no spread of contents; minor break in aseptic technique
Contaminated	Cystotomy, enterotomy, urethostomy, fresh traumatic wounds that are less than 4 hours old	There is no infection but if there is spillage of contents there is a risk of contamination; major break in aseptic technique
Dirty	Abscess, pyometra, traumatic wounds of more than 4 hours duration, perforated viscera with the presence of pus	Pus is present and area involved in surgical procedure is infected

Every aspect of a surgical procedure must be prepared aseptically and this includes:

• Preparation of the surgical environment

• Sterilization of all instruments and drapes and anything that may come into contact with the surgical site

• Preparation of the surgical site

• The surgical scrub

• Donning suitable sterile surgical attire.

Although preparation of the surgical environment may be largely done by your nursing team, it is important that you, the veterinary surgeon, understand the principles behind this vital job. It takes very little disruption to any of the routine procedures to compromise asepsis, which may lead to wound breakdown, systemic infection, reduced surgical success rate and thus inevitably the reputation of the practice.

Preparation of the surgical environment

Surgical procedures are carried out within a dedicated operating theatre. The preparation of the patient and some dirty procedures (e.g. tooth cleaning) may be carried out in the preparation room. To ensure a high standard of asepsis, practice protocols should include a strict monthly, weekly and daily cleaning routine for the operating theatre and preparation room. This is almost always carried out by the nursing staff, but it is the job of the veterinary surgeon to make sure that the task is being carried out effectively.

It is not the brief of this book to describe cleaning protocols, but there are rules governing the use of the operating theatre that should be adhered to if asepsis is to be maintained:

1. The theatre should contain only the equipment that is strictly necessary for the surgical procedure and it should be removed afterwards.

2. Only personnel involved in the procedure should be present in the theatre and should remain within the sterile area to minimize the risk of cross contamination.

3. The surgeon should concentrate on the procedure and should not be talking excessively. The act of talking releases droplets full of bacteria.

4. Body movements should be restricted as much as possible to reduce air movement and the chance of contamination.

5. All personnel should understand that they are either sterile or non-sterile and there should be no cross contamination between the two.

6. Sterile and non-sterile equipment should be identified and grouped separately and kept a reasonable distance apart to reduce the risk of cross contamination.

7. Sterile tables are sterile only at table height; gowns are sterile only from mid-chest to waist; gloved hands are sterile only from the tips of the fingers to 2 inches (5 cm) above the elbow.

8. Always hold your sterile hands together above waist height and when passing another sterilized person you should pass back to back to avoid contamination.

9. All waste must be disposed of correctly and efficiently.

Sterilization of surgical equipment

Sterilization may be defined as the destruction of all micro-organisms including bacterial spores. It is much more effective than disinfection, which destroys or removes micro-organisms but does not destroy bacterial spores.

Everything that comes into contact with the surgical site must be sterilized prior to use. This includes all instruments, drapes, swabs and all the equipment used for the procedure (e.g. orthopaedic screws, plates, fixators, drill bits, urinary catheters, feeding tubes, etc.). If sterilization is not carried out properly there is a risk of introducing infection into the body and / or the wound, which may result in wound breakdown and / or systemic infection.

Sterilization can be achieved by various methods:

1. Irradiation – the use of gamma irradiation can be carried out only in a controlled environment and is not done in practice. Prepackaged items such as needles and syringes are sterilized in this way.

2. Heat – micro-organisms are killed by high temperatures and the different methods aim to raise the temperature as high as possible.

• Boiling water – this is the simplest form of sterilization, but it is not always the most reliable. Instruments may be sterilized in boiling water, but it must be kept at a rollicking boil for at least 10 minutes. It can be used when nothing else is available, but there is a risk of melting some plastic items and blunting others.

• Dry heat – using a hot air oven. Micro-organisms are killed by oxidative destruction of their protoplasm, but they are more resistant to this if there is a dry atmosphere. To counteract this a hot air oven is designed to reach higher temperatures of 150–180°C. If the temperature is below 140°C then microbial spores will not be killed in less than 4–5 hours.

These ovens are used to sterilize equipment such as orthopaedic drill bits, glass syringes and other glass equipment, cutting instruments and powder and oil that cannot be sterilized in the presence of moisture. Fabric, plastic and rubber will be damaged by the high temperatures.

The disadvantage of a hot air oven is that a long cooling period is needed before the instruments can be handled and the moment the door of the oven is opened there is a risk of contamination by airborne organisms. There is also a risk of burning yourself and for this reason they are not recommended by the Health and Safety Executive (HSE).

• Moist heat (steam) under pressure – this is the most common method in a practice. Under normal circumstances water cannot reach temperatures higher than boiling point before producing steam but if pressure is applied, the boiling point is raised and the temperature of the steam is higher. The moisture in the steam increases the permeability of the packs of instruments and drapes to heat, which then kills the micro-organisms.

a. Pressure cooker – simple form of an autoclave. Water is boiled in an enclosed space and the air vent in the lid is closed when all the air has been driven out. The pressure then builds up to 15 p.s.i. (≈107 kPa). There is a risk of trapping a layer of air under the steam and this may not reach sufficient temperatures to sterilize effectively. The system is manually operated so there is room for human error.

b. Autoclave – there are various designs the most efficient of which are vacuum assisted and incorporate a second cycle, which removes moisture and dries the load. Most are fully automatic with a choice of programmes and have fail-safe mechanisms.

Effective sterilization relies on loading the packs of instruments, etc. correctly, making sure that there is adequate space for the free circulation of steam. Instruments must be free of grease and protein to enable the steam to penetrate and the autoclave must not be overloaded otherwise there is a risk of blocking the inlet and exhaust valves.

3. Cold chemicals – these are not always very effective and it usually takes at least 24 hours to ensure adequate sterility. Instruments and other equipment are soaked in alcohol-based chemicals or glutaraldehyde. The method is sometimes used to sterilize needles and suture materials in a shallow dish ready for use in emergencies. Chlorhexidine may also be used, but it has poor activity against bacterial spores, fungi and viruses so this is really only a form of disinfection.

4. Ethylene oxide – this gas sterilizes by inactivating the pathogen’s DNA thus preventing its replication. The sterilizer is in the form of a plastic container fitted with a ventilation system. Items to be sterilized are placed in a sealed polythene bag with a gas ampoule, which is then snapped from the outside to release the gas that permeates through the bag. Sterilization takes 12 hours, followed by 2 hours ventilation and a further 24 hours for the gas to dissipate. The process is usually done overnight and the sterilizer must be used only in a well-ventilated area away from the working environment.

Most equipment can be sterilized in this way, but the limiting factor is the size and shape of the sterilizer. It is usually used to sterilize things that may otherwise be damaged by heat (e.g. fibreoptic endoscopes, plastic catheters, anaesthetic tubing and optical equipment).