Infection and surgery

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CHAPTER 6 Infection and surgery

Principles of wound management 98

Prevention of surgical site infection 99

Antibiotics in surgery 100

Surgical infections 102

Methicillin-resistant Staphylococcus aureus (MRSA) 110

Infection and the surgeon 110

The surgical patient is exposed to potentially harmful microorganisms prior to admission, during admission and after discharge. The outside surfaces of the body, including the aerodigestive tract, are normally colonized with bacteria – a defence mechanism that is disrupted by stress and antibiotic therapy. With the prevalence of hospital acquired infections, such as clostridium difficile and methicillin-resistant staphylococcus aureus (MRSA), and the potential for blood-borne virus transmission, the practicing surgeon needs to be aware of safe antimicrobial techniques and treatments, to protect both the patient and healthcare staff. Effective communication needs therefore to be present between surgeon and microbiologist.

Principles of wound management

Classification of surgical wounds

Clean

An incision in which no inflammation is encountered in a surgical procedure, without a break in sterile technique, and during which the respiratory tract, alimentary or genitourinary tracts are not entered, e.g. varicose vein surgery, hernia repair. The risk of postoperative wound infection is about 5%.

Clean contaminated

An incision through which the respiratory, alimentary, or genitourinary tract is entered under controlled conditions but with no contamination encountered, e.g. cholecystectomy, partial gastrectomy. The risk of postoperative wound infection is about 10%.

Contaminated

An incision undertaken during an operation, in which there is a major break in sterile technique or gross spillage from the gastrointestinal tract, or an incision in which acute, non-purulent inflammation is encountered. Open traumatic wounds >12–24 h old. The risk of postoperative wound infection is >50%.

Dirty

An incision undertaken during an operation in which the viscera are perforated or when acute inflammation with pus is encountered (e.g. faecal peritonitis), and for traumatic wounds where treatment is delayed, there is faecal contamination, or devitalized tissue is present.

PREVENTION OF SURGICAL SITE INFECTION (Incorporating NICE guidelines 2008)

Preoperative precautions

• Adjust patient lifestyle. Improve diet and body mass index. Advise to stop smoking

• MRSA screening and subsequent decolonization if positive (see below)

• Consideration of delay of elective surgery if concurrent infection detected

• Advise patients to take a bath or shower using soap within 24 h prior to surgery

• If hair removal desired, use electric clippers on the day of surgery.

Postoperative precautions

• Use an aseptic technique to change dressings

• Use sterile saline to cleanse wound up to 48 h after surgery

• Patients may shower 48 h after surgery

• Use an appropriate dressing for wounds healing by secondary intention.

Antibiotics in surgery

Antibiotics are never a substitute for sound surgical technique. Pus, dead tissue and slough need removing. Antibiotics should be used carefully and only with positive indications. Prolonged or inappropriate use of antibiotics may encourage resistant strains of organisms to emerge. Except in straightforward cases, advice of a microbiologist should be sought.

Principles of antibiotic therapy

Selection of antibiotic

The decision to prescribe antibiotics is usually clinical and is based initially on a ‘best-guess’ policy, i.e. based on experience of that particular condition, what the organism is likely to be, and to what it is most likely to be sensitive. The following sequence of events usually occurs:

1. A decision is made on clinical grounds that an infection exists.

2. Based on signs, symptoms and clinical experience, a guess is made at the likely infecting organism.

3. The appropriate specimens are taken for microbiological examination, i.e. culture and sensitivity testing.

4. The most effective drug against the suspected organism is given in line with individual hospital guidelines. If doubt exists this is discussed with a microbiologist.

5. The clinical response to treatment is monitored.

6. The antibiotic treatment is altered, if necessary, in response to laboratory reports of culture and sensitivities.

Occasionally the response of the infection to an apparently appropriate antibiotic is poor. Possible causes for this include:

• Failure to drain pus, excise necrotic tissue or remove foreign bodies

• Failure of the drug to reach the tissues in therapeutic concentrations, e.g. ischaemic limbs

• Organism isolated is not the one responsible for the infection

• After prolonged antibiotic therapy, new organisms develop due to selection pressure

• Inadequate dosage or inappropriate route of administration.

Route of administration

Antibiotics should be given i.v. in severe infections in seriously ill patients. Some antibiotics, e.g. gentamicin, can only be given by the parenteral route. When the patient improves and the GI tract is functioning satisfactorily, drugs may be given orally.

It is best to avoid the intramuscular route if possible as it is uncomfortable for the patient and in shocked patients absorption would be inadequate.

Duration of therapy

This depends on the individual’s response, laboratory tests and the underlying cause of infection. For most infections that show an appropriate response to treatment after 48 h, a suitable ‘course’ should be for 5–7 days. Infections such as osteomyelitis require prolonged courses of antibiotics administered long after symptoms and signs of infection have resolved.

Dosage

The dosage may need to be modified in renal and liver disease.

Complications of antibiotic therapy

• Adverse reactions

— Side-effects, e.g. nephrotoxicity, ototoxicity

— Hypersensitivity

— Anaphylaxis

• Development of resistance

• Iatrogenic infection, e.g. Clostridium difficile with the use of cephalosporins, clindamycin.

Prophylactic antibiotics

Despite aseptic techniques, some operations carry a high risk of postoperative wound infection, bacteraemia or septicaemia. Administration of antibiotics in the perioperative period will reduce the risks.

Indications for prophylactic antibiotics

These include:

• Implantation of foreign bodies, e.g. cardiac prosthetic valves, artificial joints, prosthetic vascular grafts

• Patients with pre-existing cardiac disease who are undergoing surgical procedures including dental procedures, e.g. patients with mitral valve disease as prophylaxis against infective endocarditis

• Organ transplantation

• Immunosuppressed patients

• Diabetics

• Amputations, especially for ischaemia or crush injuries, where there is dead muscle; risk of gas gangrene is high especially in contaminated wounds; penicillin is the antibiotic of choice

• Compound fractures and penetrating wounds

• Surgical incisions, where there is a high risk of bacterial contamination, e.g. (1) clean/contaminated wounds – prophylactic antibiotics are indicated; (2) contaminated – antibiotics are given as therapy not prophylaxis; (3) dirty – antibiotics are given as therapy not prophylaxis.

Most prophylactic antibiotics are given to prevent wound infection. In some cases, they are given prior to instrumental procedures in potentially infected sites, e.g. when performing cystoscopy, when they are given to prevent septicaemia. In most cases, one dose is given preoperatively either orally if under LA (1 h preoperatively) or i.v. if under GA. The aim is to achieve therapeutic levels at the time of surgery. Individual hospital policy should be followed with regard to the use of specific agents and their duration as prophylaxis.

Specific antibiotics (→ Table 6.1)

Surgical infections

Sepsis

Sepsis is generally related to the body’s response to infection. However, sepsis is probably better defined as a group of conditions that include:

• Systemic inflammatory response syndrome (SIRS) which is defined as any two from:

— pyrexia – >38°C or <36°C

— tachycardia – >90 beats/min

— tachypnoea – >20 breaths/min

— WCC – >12 or <4

• Sepsis – SIRS plus a documented infection

• Sepsis syndrome – sepsis plus organ dysfunction and hypoperfusion

• Septic shock – refractory hypotension plus documented infection.

TABLE 6.1 Some commonly used antibiotics

SIRS is seen in many surgical patients and does not always result from an infective process. It is commonly seen in pancreatitis, trauma and burns. SIRS is a normal response to injury and in the early stages, is protective. A number of stages in the evolution of SIRS may occur:

• In the region of injury there is local production of inflammatory mediators and cytokines. These lead to vasodilatation, increased vascular permeability and the recruitment of cells that fight infection.

• In more severe injury the cytokine release has a systemic effect; this includes the production of acute phase proteins, pyrexia and an increase in peripheral leukocytes. This response is regulated by a group of counter-regulatory cytokines.

• In patients with SIRS there is an exaggerated response and the production of cytokines exceeds the counter-regulatory mechanisms. Cytokines such as IL-1 and TNF-α produce vasodilatation leading to hypotension, increased vascular permeability leading to oedema and third space fluid loss. There is also widespread activation of leukocytes that can cause damage in organs distant from the site of injury, e.g. lungs.

Management of SIRS

• Resuscitation

• Identify source of sepsis. Likely possible sources include: the wound; intravascular access (arterial, central venous, cannulas); urinary catheters/urinary tract infection; prosthetic implants; chest infection

• Administration of appropriate antibiotics – empirically initially and then changed after antibiotic sensitivities are known

• Definitive management of the course of sepsis, i.e. surgical or radiological guided drainage of abscess.

Cellulitis

A spreading inflammation of connective tissue. It is usually subcutaneous and caused by β-haemolytic Streptococci or Staphylococcus aureus.

Symptoms and signs

Redness, oedema, and localized tenderness. A scratch, insect bite, ulcer or surgical wound may be apparent. There is usually fever and malaise. Lymphangitis or lymphadenitis may be present. Lymphangitis produces red tender streaks in the line of lymphatics extending from the area of cellulitis towards the regional lymph nodes. Lymphadenitis is represented by enlarged tender regional lymph nodes. Occasionally the overlying skin is red and the glands may be fluctuant.

Investigations

Drawing a line around the erythema with permanent marker pen enables observation of progression/regression of the leading edge, and can be used to gauge response to treatment.

Treatment

Streptococcus and Staphylococcus are usually sensitive to flucloxacillin. Elevation of a limb may be required. Occasionally an abscess with thin watery pus forms and requires drainage.

Erysipelas is an uncommon skin infection caused by a Streptococcus (Group A). The condition is usually encountered on the scalp, face and neck. Pain and redness of the skin are apparent, the margin being well demarcated and raised above the normal skin. Pyrexia and malaise usually accompany the local signs. Treatment is with penicillin.

Necrotizing fasciitis

This is a rapidly progressive and potentially fatal bacterial infection that spreads along fascial planes and causes vascular thrombosis resulting in necrosis of the tissues involved. If present in a limb distal to the elbow or knee, organisms often involved include β-haemolytic streptococci and staphylococci. Coliforms and Gram-negative anaerobes may be synergistically involved elsewhere such as the scrotum (Fournier’s gangrene). Necrotizing fasciitis may result from a small puncture wound, surgical incision or penetrating trauma of a hollow viscus.

Symptoms and signs

Pain and tenderness at the leading edge of the infection can be agonizing. Redness, oedema, necrotic insensate skin patches, haemorrhagic bullae, crepitus and discharge. The patient is febrile and exhibiting signs of systemic sepsis. A test incision either at the bedside or in an operating theatre producing a grey/brown ‘dishwater’ exudate aids diagnosis, as does a ‘sweep test’ where a finger placed into the test incision and turned into the soft tissues easily separates the tissue planes digested by bacterial enzymes.

Investigations

• WBC

• Blood culture

• Swabs – culture and sensitivity

• Radiograph may show gas in tissues.

Treatment

Patients should be resuscitated and transferred urgently to the operating theatre for surgical debridement of all infected and dead tissue. A critical care bed should be requested for postoperative recovery. The tissue is usually oedematous, grey and smells. The subcutaneous fat and fascia are involved. Muscle is often viable. The microbiologist should be informed if a diagnosis of necrotizing fasciitis is suspected. Fresh specimens of tissue should be sent for urgent Gram stain and microscopy. Antimicrobial treatment is usually with clindamycin (which inhibits the production of streptococcal toxins) and benzylpenicillin intravenously. Meropenem may be used instead of benzylpenicillin in cases requiring anaerobic cover. Antibiotics are changed according to culture and sensitivities. The patient’s systemic state is observed carefully postoperatively and the wound is inspected regularly, often with a planned second look under general anaesthetic at 24 or 48 h, and any further necrotic tissue excised. When the infection has been controlled, large skin defects can be reconstructed with skin grafts. Mortality rate is about 25% in extensive cases.

Gas gangrene

Myositis and cellulitis caused by Clostridium perfringens, an anaerobic, spore-forming and gas-producing organism. The organism is found in soil and faeces. It is an infection associated with deep, penetrating, contaminated wounds usually involving an extremity, and rarely is seen as a complication of amputation of an ischaemic limb. Intravenous drug users may inadvertently inject Clostridia (perfringens or tetani) into the soft tissues. It may involve the abdominal wall following penetrating trauma of, or surgery to, the GI tract.

Symptoms and signs

Acute onset 6 h to 3 days after injury. Severe pain at site of injury. The tissues are swollen; brownish, serous, malodorous fluid may drain from the wound. Patchy necrosis and crepitus occur. The patient is toxic and may be confused or delirious. The temperature is not always elevated.

Investigations

• WBC

• Bilirubin raised because of haemolysis

• Gram-stain of discharge shows Gram-positive bacilli

• Radiograph shows gas in tissues.

Treatment

Prophylactic

Adequate debridement of wound at time of initial injury. All contused and dead tissue should be removed and the wound thoroughly irrigated and left open. Prophylactic penicillin should be given to all patients with contaminated wounds and to patients with ischaemic limbs undergoing amputations.

Therapeutic

Radical debridement of all necrotic tissue is mandatory. If the muscle of a limb is involved, amputation will be necessary. This should be done at a level where the muscle bleeds and contracts when cut. Large doses of penicillin should be given intravenously. Anti-gas gangrene serum either prophylactically or therapeutically is of unproven value.

Tetanus

This is a rare condition in the UK owing to widespread immunization. It is caused by Clostridium tetani, an anaerobic Gram-positive bacillus that produces a neurotoxin. It is found in soil and faeces. The neurotoxin enters peripheral nerves and travels to the spinal cord where it blocks inhibitory activity of spinal reflexes resulting in the characteristic features of the disease. The disease follows the implantation of spores into deep, devitalized tissues.

Symptoms and signs

History of injury

This may be as minor as the prick of rose thorn. The incubation period is 1–30 days. Muscle spasm usually occurs first at the site of inoculation and is followed by trismus resulting in the typical risus sardonicus (lock-jaw). Stiffness in the neck, back and abdomen follow together with generalized spasms, which may cause asphyxia. The muscles remain in spasm between convulsions. Opisthotonos (arching of the back and neck due to spasm) may occur. This stage is followed by convulsions which are extremely painful and during which the patient is conscious. Death may occur from asphyxia due to involvement of respiratory muscles or from inhalation of vomit with aspiration pneumonia.

Differential diagnosis

• Strychnine poisoning: the muscles are flaccid between convulsions

• Tetany: usually carpopedal spasm and does not affect the trunk

• Epilepsy

• Meningitis: there is usually only neck stiffness but convulsions may occur

• Hysteria.

Treatment

Prophylactic

• Active immunization with tetanus toxoid. All children should be immunized and this is repeated at 6 weeks and 6 months after the initial dose. Booster doses should be given at 5-yearly intervals. All patients attending an A&E department with new trauma, however mild, should have a booster, unless one has been given within the previous 5 years.

• Contaminated and penetrating wounds should be debrided and prophylactic penicillin administered. A tetanus toxoid booster dose should be given to the previously immunized patient. Those not previously immunized should be given human antitetanus immunoglobulin.

Therapeutic

1. Involve the critical care team. Discuss with microbiology.

2. Isolate the patient in a quiet darkened room. Give diazepam or chlorpromazine. In severe cases, the patient will need to be paralysed and ventilated. Feeding should be given via a fine-bore nasogastric tube. Ventilation may need to be continued for up to 4 weeks. A trial period of weaning off relaxants without recurrence of spasm will indicate when ventilation is no longer required. Tracheostomy may be required.

3. Administer penicillin, tetanus toxoid, and human antitetanus immunoglobulin.

4. Excise and drain any contaminated wound.

5. Regular physiotherapy will be required during the recovery period.

Prognosis

The mortality rate is inversely proportional to the length of the incubation period. If spasm occurs within 5 days of the time of injury, the prognosis is poor. The mortality rate is also directly proportional to the severity of the symptoms.

Methicillin-resistant Staphylococcus aureus (MRSA)

MRSA is a major nosocomial pathogen. It may cause severe morbidity and mortality. Up to 40% of nosocomial Staph. aureus infections may be methicillin resistant. They are also resistant to flucloxacillin, amoxicillin, co-amoxiclav, cephalosporins and Tazocin. Many inpatients are colonized or infected and up to 25% of hospital personnel may be carriers. The organism may be carried in the anterior nares, inguinal, perineal and axillary areas. Spread often occurs by the hands, usually of nursing or medical staff.

Risk factors for colonization

These include advanced age, previous hospitalization, length of hospitalization, stay in ITU, chronic illness, prior and prolonged antibiotic therapy, presence of a wound, exposure to colonized or infected patients, presence of invasive indwelling devices, nursing home residency.

Clinical presentation

These principally include line sepsis, surgical site infection and pneumonia.

Infection control

This includes screening of patients and staff. If MRSA is suspected, swabs should be taken from the hairline, nose, axilla, groin, perineum. Important factors in infection control include hand washing, use of gowns and gloves, isolation of infected or colonized patients (barrier nursing) and environmental cleaning.

Management

Carriers

Carriers may be treated by application of antiseptics, e.g. mupirocin to nose; use of antiseptic soaps and shampoos for five days. Check swabs should be taken at 2, 9 and 16 days after use of antiseptics.

Patients with MRSA infection

These patients should be nursed using special precautions. Vancomycin is the antibiotic of choice. Linezolid and daptomycin are alternative treatments.

Infection and the surgeon

The surgeon – as indeed are any medical, nursing, or paramedical personnel – is at risk from three main viral infections: HIV, hepatitis B, hepatitis C.

HIV

Infection with HIV is permanent and it is likely that all carriers will eventually develop AIDS. Surgical personnel are at high risk. Infection with HIV results from the passage of infected body fluid (usually blood) from one person to another. Needlestick injuries and scalpel injuries are possible sources of infection. In the general population, HIV may be transmitted by unprotected anal, vaginal, and oral intercourse, sharing needles in drug abuse, and infected blood products (e.g. as has happened in the past with haemophiliacs).

Risk categories

The following are at risk of becoming HIV-positive: homosexual or bisexual males; prostitutes (male and female); intravenous drug abusers; haemophiliacs who were treated before routine testing became available, i.e. October 1995; sexual partners of the above and children of infected mothers.

Prevention of HIV

Care at operation needs to be exercised with patients who are known to have AIDS or be HIV-positive. Patients with anorectal disease related to homosexuality, haemophiliacs and sexual partners and children of the above should be treated with appropriate caution.

Counselling is required and consent must be obtained for HIV testing. If a patient refuses and is suspected of being HIV-positive, then precautions must be taken with nursing care and any invasive procedures from simple venepuncture to major surgery.

The chance of seroconversion from a needlestick injury is approximately 0.3%.

Hepatitis B

Infection is largely blood-borne. It may be transmitted by blood transfusion; inoculation via sharp injuries from blood or blood products; droplet transmission; syringe and needle sharing in drug addicts; sexual intercourse with an infected partner; homosexual practices; tattooing or ear piercing, etc. with unsterile equipment. Antigen carriage is a risk for hospital staff, especially those in ‘high-risk’ areas, e.g. theatre staff. Dialysis units are often quoted as being a ‘high-risk’ area, but following outbreaks many years ago, all staff and patients are tested for HBsAg.

Hepatitis B vaccine is offered to all high-risk staff. These categories include: surgeons; theatre nurses; other operating department personnel; pathology department staff; A&E unit staff; liver transplant unit staff; gastrointestinal unit staff; workers in residential units for the mentally handicapped; staff of infectious and communicable diseases units.

The chance of seroconversion from a needlestick injury in unvaccinated individuals is approximately 30%.

Hepatitis C

Hepatitis C (HCV) is present in blood and spreads in the same way as HBV, by blood transfusion; syringe and needle sharing in drug addicts; mother-to-baby transmission; sharps injuries; tattooing, ear piercing, etc. with unsterile equipment; sharing toothbrushes and razors. Sexual transmission occurs but is uncommon. The incubation period is 6 weeks to 2 months. About 0.7% of the population are chronically infected with HCV.

The disease is often asymptomatic, only about 25% becoming symptomatic and jaundiced. Around 20% of those infected will clear the virus in the acute stage. Of those that do not, some will never develop liver damage; many will develop only moderate liver damage, with or without symptoms; 20% will progress to cirrhosis during 20 years or so and of that 20%, some will progress to liver failure and some will develop hepatocellular carcinoma. Carriers are a source of infection and include drug addicts; recipients of blood and blood products before September 1991; children of infected mothers; and healthcare workers from occupational injuries.

The chance of seroconversion from a needlestick injury is approximately 3%.

Precautions for the care of known and suspected hiv, hbv and hcv carriers

Sources of infection are:

• Contact – blood, urine, faeces, saliva, tears, CSF

• Air-borne – use of power tools

• Inoculation – sharps injuries, e.g. needlestick, scalpels.

Universal precautions

This refers to those precautions taken to protect theatre staff from infection in all cases. They include:

• gowns

• masks

• surgical gloves

• ‘no touch’ technique.

Special precautions

These are used for all high-risk patients, e.g. hepatitis, HIV or patients suspected of having these conditions:

• All personnel involved in patient care should be aware of the risk.

• Any patient considered as a risk should be indicated as belonging to a high-risk category on the operating list (under no circumstances should the actual disease causing the risk be placed on the operating list for reasons of patient confidentiality).

• Arrangements should be made for contaminated fluid, dressings, etc. to be handled and disposed of correctly.

Management of sharps injuries

• Let the site of injury bleed.

• Wash area with soap and water.

• Immediately report the incident to supervisor/senior officer/occupational health.

• Visit the Occupational Health Department or nearest emergency department as soon as possible.

Procedure at Occupational Health or Emergency Department

• Take detailed information – details of injury; how long ago it occurred; was the skin penetrated; did it bleed; was the sharp visibly contaminated with blood; was the source patient known to be infected and with what; any first aid measures used.

• Explain transmission risk is small.

• Offer blood test but only after appropriate counselling.

• If the source patient is known (i.e. the original user of the needle in needlestick injuries) they should be asked to consent for testing for HIV, HBV or HCV. They should be counselled before the tests are done.

• The person sustaining the sharps injury should be advised about the risks of transmission until such time as test results are received. They should practice safe sex and not donate blood.

Post-exposure prophylaxis

Hepatitis B

• If the source patient tests positive for HBV, the healthcare worker should have been vaccinated and serum antibody positive.

• If antibody levels are low, a dose of hyperimmune anti-hepatitis B IgG plus one dose of vaccine should be given.

• In the unvaccinated, one dose of hyperimmune anti-hepatitis B IgG should be given and a course of vaccination commenced.

• Similar procedures should be followed when the source patient cannot be identified or refuses to be treated.

Hepatitis C

• After 6 weeks and 12 weeks, serum analysis with polymerase chain reaction. If positive, then can give interferon and ribavirin.

HIV

• Carry out tests after counselling at 3 months and 6 months.

• No vaccine available.

• Post-exposure prophylaxis should be given within 1 hour of exposure in cases involving high-risk or known HIV carriers.

Triple agent prophylaxis may include zidovudine, lamivudine and nelfinavir.

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Infection and surgery

Specific antibiotics (→ Table 6.1)

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