Part of the TeachMe Series

Surgical Site Infection

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Last updated: December 22, 2019
Revisions: 29

Last updated: December 22, 2019
Revisions: 29

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surgical site infection (SSI) is an infection that occurs in the incision created by an invasive surgical procedure.

SSI is a leading cause of hospital morbidity, increasing ITU admission rates, doubling mortality rates, and increasing overall length of stay. Primary management is prevention through good surgical technique and patient optimisation.

The rates of SSI vary depending on the type of surgery, depending on the degree of contamination:

  • 2.1 for every 1000 operations, for clean surgery
  • 3.3 for every 1000 operations, for clean contaminated surgery
  • 6.4 for every 1000 operations, for contaminated surgery
  • 7.1 for every 1000 operations, for dirty surgery

In this article, we shall look at the risk factors, clinical features and management of surgical site infections.

Risk Factors

There are several factors that increase the risk of a surgical site infection, as shown in Table 1:

Patient Factors Operation Factors
Extremes of age

Poor nutritional state

Diabetes mellitus, renal failure, or immunosuppression

Current smoker

Preoperative shaving or site of incision

Length of operation

Foreign material in surgical site

Insertion of surgical drain

Poor closure of wound

Table 1 – Risk Factors for Surgical Site Infections

Clinical Features

The symptoms of a surgical site infection typically appear 5 to 7 days post-procedure, however can develop up to 3 weeks after (especially if a prosthesis is inserted).

The common clinical features of surgical site infections include:

  • Spreading erythema
  • Localised pain
  • Pus or discharge from the wound
  • Wound dehiscence
  • Persistent pyrexia
Fig 1 - (A) Purulent discharging forming in open wound; (B) Erythema and pus seen in closed wound; (C) drain placed in situ to remove any potentially accumulating pus.

Figure 1 – (A) Purulent discharging forming in open wound; (B) Erythema and pus seen in closed wound; (C) drain placed in situ intra-operatively

Most surgical site infections are superficial, however some may be deeper and can result in extensive wound breakdown. Fortunately, the need for debridement and open wound care is rare in clinical practice.


Any suspected surgical site infection should have wound swabs taken for culture at the wound site, especially if a purulent discharge is present (avoiding wound edges where possible to reduce skin flora contamination).

Blood tests for infection markers (FBC, CRP) should be taken, alongside blood cultures if any evidence of systemic involvement or sepsis.


Any sutures or clips present should be removed, allowing for the drainage of any pus and the opportunity for wound packing if required.

Empirical antibiotic should be started; different wounds are often caused by different organisms (e.g. a laparotomy wound infection is more likely to be caused by a coliform), however best practice is to follow local empirical antibiotic guidelines, tailoring antibiotic therapy following culture results


The prevention of surgical site infections can be achieved in the pre-operative, intra-operative, and post-operative settings.

Pre-Operative Phase

  • Give prophylactic antibiotics if indicated (clean surgery involving a prosthesis, clean-contaminated surgery, or contaminated surgery)
  • Do not remove hair routinely – if necessary do this immediately prior to surgery with an electric clipper
  • Patient advice – shower prior to surgery, encourage weight loss, optimised nutrition (to promote wound healing), good diabetic control, and smoking cessation

Intraoperative Phase

  • Prepare the skin at the surgical site immediately before the incision using an antiseptic preparation (povidone-iodine or chlorhexidine are most suitable)
  • Change gloves or gowns if contaminated
  • Use an appropriate interactive dressing at the end of the operation to cover all surgical incisions

Post-Operative Phase

  • Monitor wounds closely – the use of see-through dressings* will limit the number of dressing changes, thus minimising the chance for bacterial contamination
  • Ensure that wounds in difficult areas such as skin creases and underneath skin folds (such as groin) are closely observed
    • Patients may require pads to separate the wound from overlying skin or be bed bound to remove pressure on a wound
  • Refer to a tissue viability nurse for advice on appropriate dressings for the management of surgical wounds that are healing by secondary intention

Topical antibiotics are used in some cases post-operatively as well; a meta-analysis has shown that topical antibiotics probably do prevent SSI rates when compared with no topical antibiotic or antiseptic therapy

Key Points

  • Surgical site infections are a leading cause of in hospital morbidity, rates dependent on the type of surgery performed
  • Often appearing 5-7 days post-operatively, symptoms include spreading erythema, localised pain, pus/discharge from the wound, or a persistent pyrexia
  • Primary prevention is the optimal way in reducing surgical site infections, with several evidence-based interventions possible
  • Any case of surgical site infection should be regularly monitored, with any clips or sutures removed where feasible, any pus present is suitably drained, and empirical antibiotics prescribed