In the light of the multiple routes of transmission noted above, the key principles that underpin modern infection control procedures are shown in Table 7.2. These apply in all healthcare settings, including dental surgery.
Table 7,2 Principles of universal infection control
Many different pathogenic microorganisms pose a problem
There are many sources of infection Any patient might be a carrier of pathogenic microorganisms Routine procedures must be effective in preventing cross-infection All blood, regardless of source, is potentially infectious The same cross-infection control procedures must be used for all patients
Table 7.3 Key elements of universal infection control
Medical history Cleaning instruments Sterilising instruments Use of disposables
Decontamination of operatory surfaces Protective work wear Avoiding needlestick injuries Immunising staff Safe waste disposal Effective training of staff
First, although there is widespread concern about blood-borne viruses such as HIV, a wide range of pathogenic microorganisms is encountered in clinical practice. Thus, attention must be given to preventing the spread of all infections, both rare and common.
Second, there are many potential sources of infection, most of them unrecognised. For example, carriers of hepatitis B virus frequently appear clinically well and are unaware of their carrier status. Similarly, patients could be colonised by antibiotic resistant bacteria, such as methicillin resistant Staphylococcus aureus (MRSA), with no outward clinical signs or symptoms. Thus any patient, regardless of background or medical history, must be considered to pose an infection risk.
The logical conclusion to these concepts is the adoption of universal infection control, whereby every patient is treated as a potential carrier. The infection control protocol adopted must be sufficiently stringent to reduce the risk of contamination of patients or staff to a level that is highly unlikely to cause infection. It also follows that patients who are known carriers of pathogens, including blood-borne viruses, will pose no additional risk and can be treated safely under the same operating conditions.
Key elements of universal infection control
The key elements of universal infection control are listed in Table 7.3 and will be discussed in turn.
The collection of an accurate medical history is part of good clinical practice and is helpful in the identification of immunocompromised patients. However, although a medical history can provide useful information in respect of previous infectious diseases the clinician must be aware that it does not allow for the categorisation of patients into 'high risk' and 'low risk' from the point of view of infectivity to staff and other patients. One current exception to this concept relates to patients who fall into the risk groups for CJD (see below).
The cleaning of used surgical instruments to remove visible deposits is an essential step prior to their sterilisation. In hospitals, both the cleaning and the subsequent sterilisation procedures are usually performed in a Central Sterile Supply Unit (CSSU). However, increasing amounts of minor surgery are performed in primary care and, under these circumstances, the decontamination of used instruments might be performed in a medical or dental practice. In such cases, instrument cleaning may be achieved by hand scrubbing in soap or detergent, but ultrasonic baths and washer disinfectors are very useful and more effective for many items. Heavy-duty protective gloves should be worn during instrument cleaning, and care taken to avoid sharps injuries.
After clinical use, all surgical instruments must be sterilised before they are used to treat a subsequent patient. The sterilisation method of choice for heat-stable instruments is the autoclave. It is critical that the steam makes physical contact with the surfaces of all the instruments and care must be therefore be taken not to overload the autoclave and impede steam penetration. Effective monitoring of autoclave efficacy is important. Physical, chemical and biological tests of efficacy are available; for example, a chemical indicator strip can be placed in the centre of the load as a check on the effectiveness of each cycle of a bench-top autoclave.
Hot air ovens are microbiologically acceptable as a sterilisation measure and are used for specific purposes, such as the sterilisation of greases. However, the higher temperature and longer cycle time (160°C for 60 min) make them more damaging to instruments and they are not ideal for routine sterilisation procedures.
Chemical agents such as aldehydes are not appropriate for routine sterilisation of surgical items and equipment. They are unreliable and some are toxic or corrosive. However, for certain expensive, heat-sensitive items such as endoscopes, high level disinfection with chemicals, under strictly controlled conditions, is employed.
In the light of concerns over the resitance of prions to sterilisation procedures, there are now calls for the 'tagging' (e.g. by bar coding) of all individual surgical instruments. This would permit the recording, in a patient's notes, of exactly which instruments were used and so introduce 'traceability' of instruments into the recycling process. It would, however, be a massive logistical exercise with major cost implications.
Disposable items are generally recommended, although there is a cost implication. Disposable items must always be used once only and then discarded. The routine use of disposable instruments for surgery involving tissues that pose a risk from vCJD, for example tonsillectomies, has been recommended in the UK.
As needles cannot be reliably cleaned and sterilised, they must always be discarded into a sharps bin after use on a single patient. Similarly, a local anaesthetic cartridge must never be used for the treatment of more than one patient.
Good hygiene in healthcare facilities is an important and underrated element of infection control, with particular relevance to surgical sepsis. In addition to general environmental contamination, surfaces in clinical areas can become contaminated with microorganisms following contact with tissues and body fluids of patients. Regular cleaning of surfaces with detergent, together with application of disinfectants in appropriate sites, are essential. Other 'surfaces' can also pose a problem, for example the pens used by healthcare workers, many of which have been shown to be contaminated with pathogens such as MRSA.
In the event of an overt spillage of blood or other body fluid, it should be soaked into an absorbent cloth and a disinfectant such as hypochlorite (lOOOOppm available chlorine) applied. Alternatively, commercially available spillage granules could be used.
All staff should wear protective coats on wards to protect their outdoor clothing from contamination. However, white coats themselves become contaminated with microorganisms, especially at points of frequent contact, such as the sleeve and pocket. Indeed, the uniforms worn by healthcare workers have been shown to play a role in transmitting bacteria in the hospital setting and the importance of hygiene, with regular laundering of uniforms, should again be stressed. Appropriate theatre dress, including operating gown, gloves and eye protection must be worn routinely when undertaking surgical procedures, together with a well-fitting surgical facemask.
Sharps injuries are common among staff performing surgical procedures and many go unreported to occupational health departments and so are not followed up. However, occupationally acquired infections with hepatitis B and C viruses, and with HIV, have been recorded following needlestick injuries and related sharps accidents. It is, therefore, essential that healthcare workers are encouraged to seek appropriate management following such incidents. The principles of management of needlestick and related injuries are discussed below. Although some of these injuries are unavoidable, many are essentially preventable and great care must be taken when handling and disposing of all sharps.
Needles should never be resheathed after use, unless a safe resheathing device is used. Care must also be taken not to injure other staff, for example when sharp instruments are being passed between surgeons and nurses. Unsheathed needles must never be left exposed where others might injure themselves. All contaminated sharp items must be discarded into a sharps box (see below) and staff must never put their hands into the opening of the box.
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