Page created on August 31, 2021. Last updated on September 10, 2021 at 17:54

Postoperative wound infection

Introduction

Infection of postoperative wound, also called a surgical site infection, is one of the most common complications of postoperative wounds. They account for high morbidity and mortality. The majority of cases occur due to endogenous bacterial flora which is present on the mucous membranes or skin.

By definition, postoperative wounds must be infected within 30 days post-surgery. However, most cases occur after 3 – 7 days.

Etiology

The most common offending bacteria are staphylococcus aureus, coagulase-negative staphylococci, enterococci, and E. coli.

There are both patient-related risk factors and procedure-related risk factors for postoperative wound infection.

Patient-related risk factors:

• Old age
• Malnutrition
• Obesity
• Steroid use
• Diabetes
• Smoking

Procedure-related risk factors:

• Formation of haematoma at the site of the wound
• Leaving drains in the wound
• Leaving dead space in the wound
• Long and difficult surgery
• Poor preparation of surgical site

Clinical features

A postoperative wound infection will have clinical features similar to other infected wounds:

• Erythema
• Localised pain
• Unexplained fever
• Purulent discharge from the wound
• Wound dehiscence (see below)
• Delayed wound healing

Diagnosis and evaluation

The diagnosis is made based on clinical evaluation of the wound, including presence of the clinical features. A microbiological sample from the wound should be taken to isolate the microbe. If it’s suspected that the infection is deep, imaging with ultrasound or CT/MRI may be useful.

Treatment

All postoperative wounds are treated with wound exploration (opening) and serial (repeated) debridement and dressing changes. These wounds are often left to heal by secondary intention rather than primary closure. Moist dressing facilitate healing. Antibiotics are necessary only if the wound is deep or if the infection is systemic.

Negative pressure wound therapy, also called vacuum-assisted closure, refers to the use of a device which applies subatmospheric pressure to the wound surface. This facilitates wound healing and may be used.

Prevention

Proper operative risk stratification, preoperative skin preparation, maintenance of operating theatre sterility, and the use of prophylactic antibiotics, are the most important measures to prevent postoperative wound infection. The type of prophylactic antibiotic depends on the type of surgery. For most surgeries the choice is usually cefazolin.

Other disturbances of wound healing

Factors which impair wound healing

• Poorly controlled diabetes
• Peripheral vascular disease
• Smoking
• Malnutrition
• Immunosuppression

Wound dehiscence

Wound dehiscence refers to when a wound which has been closed, reopens. This may cause bleeding, pain, and inflammation, and predisposes to infection. It mostly occurs secondarily to a wound infection. It may also occur due to improper wound closing which puts too much tension on the wound, or if the patient does not follow instructions to avoid heavy lifting. The wound must be cleaned and debrided before it can be surgically closed again.

The worst type of wound dehiscence is “burst abdomen”, in which a laparotomy wound bursts open. It may be partial (bowel not eviscerated) or complete (bowel eviscerated). In either case, this is a surgical emergency which must be emergently treated in the OR.

Incisional hernia

Incisional hernia, hernia through an incompletely healed abdominal surgical incision, occurs in 10 – 15% of patients. It occurs most commonly in obese and those with poor abdominal muscle tone. It presents as an abdominal bulge at the site of the incision. In some cases, the separated edges can be palpated.

These hernias may be closed surgically if necessary or managed expectantly.