4.1. INTRODUCTION
Many admissions to the surgical wards of hospitals are emergencies with infectionrelated pathology such as acute appendicitis, peritonitis, empyema of the lung, osteomyelitis - and the surgical procedure and antibiotic therapy administered are designed to treat that infection. Patients admitted for elective surgery are, however, at risk of developing surgical wound or other nosocomial infections. These include pneumonia, urinary tract, intra-abdominal or periprosthetic infection with septicaemia which may lead to multiple organ dysfunction and death. Despite the widespread and often excessive use of antimicrobials, infection remains the most common postoperative complication in most forms of surgery with associated morbidity and mortality and is a frequent cause of the patient's death. Its prevention wherever possible is therefore crucial.
There are many reasons why patients develop HAL Some of these relate to the immunocompetence of the patient - while others reflect the environment in which the patient is nursed or the skill of the surgeon and the team conducting their care. The incidence of infection varies widely - but it has been estimated that 10% of all patients entering UK hospitals develop a nosocomial infection.
The cost of nosocomial infection is a major burden to the Health Service and relates to additional in-patient days, further surgical intervention, antibiotic (and other pharmacy) costs and investigations.
In many patients post-operative wound infections do not present until after their discharge, and this has been occurring more commonly with the reduction in hospital stay. 40 - 60% of these wound infections are now diagnosed and treated in the community. The additional cost there comprises district nursing time, wound dressings and antibiotic costs. There is also a cost to the patient who cannot return to work and may have to be re-admitted to hospital for further surgical intervention.
Certain invasive interventions and investigations require particular care in infection prevention, and in some intravenous antimicrobial prophylaxis is mandatory.
4.2. RISK FACTORS FOR INFECTION
4.2.1 Definition of Infection
The incidence of postoperative infection is widely used in clinical research and audit. A satisfactory definition of these infections as outcome indicators can, however, be difficult - but the Centres for Disease Control in the USA (address in Appendix 5) has issued definitions which are widely employed20. It is important to recognise that infection is clinically diagnosed and microbiological results are then used for confirmation. In urinary tract and neurosurgical situations, microbiology is considered essential in order to define infection.
A wound infection may be defined as the presence of a purulent discharge in, or exuding from the wound - or a spreading erythema indicative of cellulitis around the wound. It is, however, important to recognise that this infection may be secondary to some other complication. Thus the discharge of a seroma, haematoma or of urine, gastro-intestinal contents, pancreatic juice or bile from the wound indicates some other complication which has resulted in the wound becoming infected secondarily.
There are many reasons why a patient might develop a wound or other infection. These factors can be considered under three headings - bacterial contamination, the surgical wound and patient immunocompetence.
4.2.2 Bacterial Contamination - Classification of Operations
Operations have been classified according to the risk of bacterial contamination at the time of operation. Four categories have been internationally recognised.
It is important to recognise that an operation is classified at the time of surgery, on the basis of disease aetiology and the events occurring during the operation - not on the outcome of that operation.
4.2.2.1 Clean
Clean operations are those in which no infection is encountered in the skin or deep tissues, no break in aseptic technique occurs in the operating theatre and the bacterially colonised tracts of the body (gastrointestinal, genito-urinary or respiratory) are not entered.
4.2.2.2 Clean Contaminated
These are operations in which the gastrointestinal, respiratory or genitourinary tract is entered but where no significant spillage of the luminal content arises and unavoidable bacterial contamination is minimal.
4.2.2.3 Contaminated
A contaminated operation is one in which acute inflammation (without pus) is encountered during the procedure or in which there is uncontrolled spillage of luminal contents from the gastrointestinal, respiratory or genitourinary tracts during surgery. Should a break in aseptic technique occur during the operation it should be classified in this category as should those operations occurring within four hours of the trauma which necessitates the surgery.
4.2.2.4 Dirty
An operation is classified as dirty if frank pus is encountered or the abdomen is opened for a perforated viscus. An operation performed more than four hours after the trauma would also be included in this group.
4.2.3 Source of Bacterial Contamination
The more heavily contaminated a wound is with bacteria, the greater the risk of infection. This is the basis of the classification of operations given above. Organisms causing the infection are either of exogenous or endogenous origin. Exogenous organisms are those transmitted to the patient from the environment or by contact from health care workers and these are the most important in clean wound infection. It has become apparent, however, that most bacteria causing wound infection are endogenous to the patient, that is they already exist in or on the individual, and may include bacteria acquired in hospital prior to surgery.
4.2.4 The Surgical Wound
The degree of tissue damage and trauma is a determinant of the incidence of postoperative infection and is a reflection of surgical expertise. Surgical expertise remains the major determinant of whether a patient develops postoperative infection or not. Necrotic tissue or a haematoma arising from inadequate haemostasis is an ideal medium for bacterial growth. Tissue ischaemia caused by prolonged use of mechanical retractors or too tight suturing of skin edges will increase the risk of infection further. A smaller bacterial inoculum is also able to cause infection when a foreign body is present in the tissues. Foreign body implants are commonly essential to the operative procedure - but injudicious use of non-absorbable sutures etc. only serves to increase this risk. Drains also increase the risk of an anastomotic dehiscence and of wound infection whether open or closed suction-type drains are used. Their use should therefore be restricted to a minimum.
4.2.5 Patient Immunocompetence
There are many factors which affect the ability of the patient to resist bacterial contamination, arising during surgery. Extremes of age, obesity or malnutrition, diabetes, cirrhosis, malignancy, steroid or cancer therapy, leueopenia or immunocompromising diseases (such as HIV infection) all reduce the patient's ability to resist infection. The American Society of Anaesthesiology (ASA) grade of fitness was designed to assess the patient's status pre-operatively. It has also been shown, however, to be a useful indicator of patients' susceptibility to infection21. Other factors known to affect adversely the incidence of infection include the length of the operation22 the use of blood transfusion23 and splenectomy24
4.2.6 Audit of Infection
Audit of clean wound infection has been proposed as a quality indicator for hospitals. Infection can, however, be difficult to define - and surveillance would have to be carried out in the community and for up to one year after, for example, prosthetic implant procedures if the true incidence is to be determined.
A cycle of audit to assess the incidence of surgical wound infection, urinary tract infection after catheterisation, infection in patients having continuous ambulatory peritoneal dialysis and septicaemia after central venous catheterisation has been proposed (see 1.4.15.3). Meaningful outcomes from audit should be implemented in order to close the audit loop. Health Boards, Trusts and GPs should agree which audits are appropriate and these should form part of the agreed specifications in contract negotiations.
4.3. PREVENTION OF INFECTION
4.3.1 Patient Preparation
Individual surgical units should develop good practice protocols designed to minimise the risk of HAI in patients undergoing surgical procedures. Such protocols should where possible be based on evidence based studies, e.g. the importance of bowel preparation prior to elective colorectal procedures is now accepted as standard.
4.3.2 Theatre Ventilation and Operating Rituals
4.3.2.1 Theatre Ventilation
The purpose of operating theatre ventilation is to provide a safe environment for the patient and one in which it is comfortable for the surgical team to work. It is also important to remove anaesthetic gases safely. Bacteria can be transported to the operation site on airborne particles largely generated by skin scales from the nursing, medical (and other) staff present in the operating theatre. The number of attendants in the theatre should therefore be kept to the minimum necessary and movement of staff within the operating theatre discouraged.
4.3.2.2 Clean Ventilation
In a conventional operating theatre, air should be maintained under pressure to ensure an outflow from the theatre and the inflow of air filtered to remove particles above 5 microns in diameter. The air should pass from diffusers on the ceiling to low level wall extractors and air should normally flow from the preparation or laying-up room to the operating theatre, to the scrub-up room, anaesthetic room and out of the theatre complex. Air delivered to the suite should contain less than one colony of Clostridium spp or Staphylococcus aureus per m' of air. Aerobic cultures on non-selective media should indicate not more than 35 bacteria carrying particles (BCP) per M3 of circulating air. These tests should be done, using a Casella slit sampler or suitable portable system, on commissioning the operating theatre and following any work done on the ventilation system.
4.3.2.3 Laminar Flow Ventilation
Laminar flow ventilation systems utilising high efficiency particulate air (HEPA) filters are recommended for ultra-clean, implant surgery. This gives a more rapid rate of exchange of the air and ensures that the air passes in a non-turbulent fashion over the operating site.
Further information on the policy, design and validation of operating theatre ventilation systems is contained in a HTM25 with further advice available from the HEEU (address at Appendix 5).
4.3.2.4 Pre-packed Sterile Equipment
NHS MEL (1998)44 26 reminded Trusts that from 14 June 1998 all medical devices marketed in Europe must comply with a European law - the Medical Devices Directive (93/42/EEC). As a result many items of equipment, prostheses, catheters etc. are now purchased sterile in pre-packed containers for single use only.
Medical devices manufactured by an NHS Trust, Health Board or NHS Agency, e.g. prosthetics, laundered reuseable theatre gowns and drapes, or Sterile Services Department (SSD) products, must comply with the Regulations if they are supplied to another separate legal entity (e.g. NHS Trust, NHS organisation, independent or voluntary health care provider or to anyone in the private sector). Further information is given in MDA Directives Bulletin 18A 15.
European standards (EN 50103, EN 724, BS EN 90000: Quality management and quality assurance and BS EN 46000: Specification for the application of the above to the manufacture of medical devices) support the Directive and lay down standards of manufacturing that represent good practice. To comply with health and safety and consumer protection legislation it is recommended that NHS in-house manufacturing operates to these standards even if products are not supplied to a separate legal entity.
Where a change of supplier is planned the ICT/Officer should be informed in order to ensure that appropriate quality standards are maintained. Single use items must never be reused as this may result in legal action under the Consumer Protection Act and/or Health and Safety at Work Act (see Appendix 2)27.
4.3.2.5 Protective Clothing
All groups of healtheare workers, whether based in hospital or the community, should carry out a risk assessment to establish the requirement for protective clothing. A protocol should then be produced which clearly specifies the requirement for items such as gowns, gloves, masks, (with or without filters, hoods/caps and eye shields) together with detailed instruction as to when they should be worn. It is also important that individual items are specified in sufficient detail to ensure that infection control principles are not compromised by the procurement of inferior quality items in an attempt to reduce costs.
4.3.2.6 Cleaning, Disinfection, Sterilisation
HICCs/TICCs are responsible for producing a policy covering all aspects of cleaning, disinfection and sterilisation procedures for equipment and the working environment. All instruments must be thoroughly cleaned prior to disinfection/sterilisation. Further advice is to be found in "Sterilisation, Disinfection and Cleaning of Medical Equipment"28, HTM 20 1014 and HTM 203029. Procedures are included in the Advisory Committee on Dangerous Pathogens (ACDP) guidance 30 for the handling of surgical instruments potentially contaminated with the agent responsible for Creutzfeld-Jacob Disease (CJD). (It should be noted that this guidance is currently under review, all concerned should remain alert for any changes in this advice once the revised guidance is available.)
4.3.2.7 Laundry
All linen from patients with proven infection and linen contaminated with blood or blood stained body fluids should be placed in a red "Infected linen" alginate or water soluble bag and sent for decontamination (see Hospital Laundry Arrangements for Used and Infected Linen 31).
4.3.2.8 Clinical Waste (including Sharps) Disposal
See Chapter 7.
4.3.3 Prevention of Bloodborne Viral Infection
Trusts should ensure that all staff involved in exposure prone procedures have been successfully vaccinated against Hepatitis B 32 (see Chapter 8). Trusts should have policies and nursing procedures in place for all aspects of Hepatitis B, C or HIV infection in the hospital environment.
4.3.4 Staff Changing Accommodation
There should be adequate staff changing and shower facilities, ideally separate from ward areas. Staff engaged in surgical and investigational procedures should be encouraged to shower after work and to wear clean work clothing daily. Sufficient uniforms must be provided to allow for delays in laundered garments being returned for use. Staff should be discouraged from either going home in uniform or taking uniforms home to wash.
4.3.5 Ward Accommodation
To prevent spread from patients with infectious diseases such as Clostridium difficile associated diarrhoea, tuberculosis, or those contaminated with resistant organisms such as MRSA or vancomycin resistant enterococci (VRE), single room isolation facilities should be available. Access to the isolation rooms should be restricted to authorised personnel only. The number of single rooms and the number and type of mechanically ventilated single rooms should be assessed according to the health care facility's activity and against any centralised resources such as an isolation unit. In a new build 24 bedded ward, this assessment should be made against a recommendation that four of the single rooms should be mechanically vented in order to meet the following requirements;
a) each room should be capable of being held at a positive pressure relative
to adjacent communication spaces and at a slightly positive pressure relative
to the room's associated sanitary facility;
b) additionally, each room should also be capable of being held at a negative
pressure relative to adjacent communication spaces and to that room's associated
sanitary facility;
C) a local control and status indication panel for these single rooms is
required to show the pressurisation status of each room and to allow local control
to alter the pressurisation of each room from positive to negative as required
by the clinician.
Air movement, induced by mechanical ventilation, should be from clean to dirty areas where these can be defined. The design should allow for an adequate flow of air into any space having only mechanical extract ventilation via transfer grills in doors or walls. Such arrangements should avoid the introduction of untempered air and should not prejudice the requirements of fire safety or privacy.
Ventilation supply plant should include air filters having a minimum air resistance of 85% in accordance with British Standards (BS)33.
A separate extract system will be required for "dirty" areas, e.g. the sluice and disposal and sanitary facilities, and external discharge arrangements for extract systems should be protected against back pressure from adverse wind effects and should be located to avoid reintroduction of exhausted air into the building through air intakes and windows.
Surfaces within the isolation room should be easy to clean, impervious to water and damage-resistant from disinfectants.
Guidance on building and engineering matters should be sought from the HEEU (address in Appendix 5).
4.4. INVESTIGATIONAL AND THERAPEUTIC INVASIVE PROCEDURES
4.4.1 Endoscopes
Endoscopic procedures are now performed for a wide range of indications. The risk of transmission of infection is low provided the instrument is adequately cleaned and disinfected after use. Trusts must ensure that there are clear policies and procedures for the cleaning, disinfection, sterilisation and storage of these items including details of any chemical agents to be used, the contact times and any precautions necessary to ensure safety of staff involved. Detailed guidance on the cleaning and disinfection of endoscopes is to be found in the following documents.
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Gastrointestinal endoscopes |
British Society of Gastroenterology |
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Working Party Report34 |
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Cystoscopes |
British Society of Urological Surgeons |
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Working Party Report35 |
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Bronchoscopes |
British Thoracic Society |
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Working Party Report36 |
Further advice is to be found in MDA Device Bulletin DB 9607 199637
4.4.2 Intravascular Devices
Intravascular catheter-related infections are associated with increased morbidity and mortality, prolonged hospitalisation and increased medical costs. Devices include those for short term access and indwelling catheters, peripheral venous and arterial cannulae, peripherally inserted central venous catheters, pressure monitoring systems, cardiac catheters, pacemakers and haemodialysis equipment.
HICCs, in collaboration with specialist units, should produce guidelines for the prevention of intravascular device-related infection, which will include:
This guidance should, where appropriate, be incorporated into the local Nursing Procedures Manual for Hospital Staff and may also be readily adapted for use in the outpatient or home care situation.
4.5. ANTIBIOTIC CONTROL MEASURES
4.5.1 Antimicrobial agents currently account for approximately 15-20% of current NHS hospital pharmaceutical spending. The great increase in the range and diversity of antimicrobial agents has resulted in the more rapid resolution of infection in many clinical situations. These advances have, however, magnified the problems associated with misuse of antibiotics - spiralling costs and financial waste, and the growing problem of multiple antibiotic resistant organisms which require additional infection control policies and procedures.
To attempt to minimise these problems it is recommended that Trust Pharmacy and Therapeutics or Medicines Committees should consider introducing measures to promote good practice in relation to antibiotic prescribing38.
Recommended measures include:
A close working relationship between the microbiology laboratory, its consultants and their clinical colleagues is essential to ensure appropriate and effective antimicrobial chemotherapy. The microbiology laboratory also plays a pivotal role in the surveillance of antibiotic sensitivity/res stance within hospitals and the community, and the dissemination of these data to individual wards and clinicians or the primary care sector. These data should not be considered in isolation but rather correlated with data on the surveillance of hospital wound infection gathered by the ICT. Where practicable any hospital based prescribing policy should be linked to its sister policy covering antibiotic primary care prescribing in the community.
After consultation with surgeons, microbiologists and pharmacists, a local formulary should incorporate a written policy for surgical prophylaxis recommending specific antibiotics together with clear instructions regarding the timing and route of administration, dosage and duration. All surgical specialties should be included and the policy reviewed regularly.
The administration of antibiotics before or during a surgical operation can significantly reduce the rate of surgical wound infection. These prophylactic antibiotics support the body's own defence mechanisms which counter any contamination. Prophylaxis is distinct from therapy where antibiotics are administered for therapeutic reasons in order to treat pre-existing infection. Prolonged use of antibiotics used in prophylaxis is not appropriate, may mask the diagnosis of post-operative infection, lead to the emergence of multi-resistant bacteria and can be financially wasteful. An infection risk assessment must be performed before deciding on the appropriate regimen.
4.5.2 Prophylactic antibiotics
There are some operations in which endogenous or exogenous bacterial contamination of the operative field is inevitable. In such patients a prophylactic antibiotic should be administered before the contamination occurs in order to prevent that contamination leading to infection of the tissues. The role of prophylactic antibiotics is to support the body's ability to resist the contamination. Where the tissues are already infected IV bactericidal antibiotics are administered for therapeutic reasons, and a longer course of therapy may be required. It is recommended that Trusts have a policy for prophylactic antibiotic use which should define the operations for which they are to be used, the antibiotic to be employed and its dose, duration, time and route of administration.
4.5.2.1 Indications
A prophylactic antibiotic should be administered whenever one of the bacterially colonised tracts of the body is opened at an operation classified as clean-contaminated or contaminated. This would include operations on the antra and sinuses of the skull, the pharynx, gastro-intestinal tract, upper and diseased lower respiratory tract, genito-urinary tract, and the biliary tract in the presence of jaundice, common bile duct stones (or stricture) or in elderly patients, also those operated on for compound trauma.
4.5.2.2Drug Selection
The choice of antibiotic used for prophylaxis will depend upon the operation being performed and the organisms most likely to contaminate the operative field. Thus in implant surgery Staphylococcus aureus and Staphylococcus epidermidis are the common pathogens - whereas in colonic surgery the Gram-negative aerobic bacilli and anaerobes predominate. The role of enterococci as primary surgical pathogens following gastro-intestinal surgery is debatable -although this organism may be important in the colonisation and infection of prosthetic heart valves.
The increasing problems of MRSA raise many controversies. The use of glycopeptides for prophylaxis cannot generally be recommended.
An agent with an adequate but as narrow a spectrum of activity as possible should be used to avoid disturbing the natural colonisation resistance conferred by the normal flora.
4.5.2.3 Duration of Administration
There is little evidence to suggest that more than single dose prophylaxis is required in any area of surgery unless the operation continues for more than two hours or there is more than two litres of blood loss in the adult patient. The use of prolonged courses of "prophylaxis" cannot be justified and only serves to assist in the development of resistant bacteria in our hospitals.
4.5.2.4 Timing of Administration
Commonly prophylactic antibiotics are selected to be bactericidal and are administered IV immediately prior to the operation such that there is a high circulating blood level at the time of operation, the time of maximal bacterial contamination and for a few hours thereafter. Where contamination occurs unexpectedly during an operation the antibiotic should be administered immediately.
To ensure a high circulating blood level at the time of operation intravenous administration on induction of anaesthesia is the preferred route for many surgeons.