Surgical site infection - Perioperative care

Surgical site infection

Definition

Surgical site infections include superficial site infections (skin and subcutaneous tissues), deep site infections (involving fascia and muscle layers) and organ or space infections (such as abscess, bone infections, etc).

Aetiology

Superficial and deep site infections occur due to Staphy-lococcus aureus (including MRSA), Staphylococcus epi-dermidis (specific association with prosthetic materialincluding cannulae) and Streptococci or mixed organisms. The organisms responsible for organ or space infections are dependent on the site and the nature of the surgical condition, e.g. anaerobic organisms in bowel perforation or anastomotic leaks, Streptococci and Staphylococci in bone infections. The risk of surgical site infection is dependent on the procedure performed. Contaminated wounds such as in emergency treatment for bowel perforation carry a very high risk of infection.

Patients at particular risk include the elderly, malnourished, immunodeficient and those with diabetes mellitus.

Clinical features

Superficial infections appear as a cellulitis (redness, warmth, swelling and tenderness) around the wound margin, there may be associated lymphadenopathy. It may be of value to draw round the area of erythema to monitor progression and response to treatment. Deeper infections and collections may present as pyrexia with few external signs. Specific presentations depend on the site, e.g. peritonitis or pus discharging from surgical drains.

Complications

Localised infections, especially in high-risk patients may spread to cause generalised septicaemia and septic shock. Wound dehiscence (total wound breakdown) is rare. It is preceded by a high volume serous discharge from the wound site and necessitates surgical repair.

Investigations

Pyrexial patients require investigations. Paired aerobic and anaerobic blood cultures should be taken (preferably during pyrexial episodes) and any pus or wound discharge sent for microscopy and culture. Patients with pyrexia and no obvious localising signs or symptoms may require imaging such as ultrasound, CT scanning or isotope bone scanning to identify the source of infection.

Management

Prophylaxis against infection includes meticulous surgical technique and the use of prophylactic antibiotics. Severely contaminated wounds may be closed by delayed primary suture. Contaminated cavities, such as the abdomen, require the placement of surgical drains.

Where possible the underlying cause of the infection should be treated, e.g. removal of infected material, closure of anastomotic leaks.

Superficial surgical site infections may respond to antibiotics (penicillin and flucloxacillin, depending on local policy). Deeper surgical site infections may require the removal of one or more skin sutures to allow drainage of infected material. Abscesses generally require drainage either by surgery or radiologically guided aspiration alongside the use of appropriate antibiotics.