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Surgical site infections: understanding the problem

Surgical site infections: understanding the problem

What is a surgical site infection?

A surgical site infection (SSI) is an infection that occurs after surgery in the part of the body where the surgery took place

SSIs can be categorised according to the layers of tissue the infection infiltrates.  In some cases the infection may be superficial involving the skin only, while in other cases they can be more serious and can involve tissues under the skin, organs, or implanted material (such as an artificial joint).

What are we trying to achieve?

Healthcare associated infections (HCAIs) are the most common complication affecting patients in hospital and SSIs are the second most common HCAI after catheter-associated urinary tract infections.

SSIs are a major burden on patients and on health resources.  SSIs increase mortality[1] , readmission rates, length of stay[2] , and can have a devastating effect on patients and their families.

In February 2012 we recognised that we had a limited understanding of the number of patients who develop SSI.  We undertook a project (Patient Smart SSI Rigour Project) to measure the rate of SSI across selected orthopaedic surgeries, including hip, knee and other joint replacement surgery, and ankle and neck of femur fracture repair.

Orthopaedic procedures were chosen because a large number of procedures are performed annually, a large majority are considered ‘clean’ site surgery, the significant impact to patients and costs for these procedures, alignment with international approaches to SSIs, and a high level of interest from our orthopaedic service.

Value: Better, Best BrilliantOur aim was to:

  • identify data sources
  • accurately measure the rate of surgical site infection across selected procedure types
  • review rates of infection to identify areas of concern and plan improvement activity

  1. It has been reported that over one-third of postoperative deaths are related, at least in part, to SSI: Astagneau P, Rioux C, Golliot F, et al. Morbidity and mortality associated with surgical site infections: results from the 1997–1999 INCISO surveillance. Journal of Hospital Infection 2001;48:267–74
  2. On average increasing a patient’s hospital stay by 7.4 days, at a cost of $1000 per day. Each DHB could potentially save $21,000 for every SSI avoided. Sapere Research Group SSI Cost Benefit Analysis


What have we done?

We reviewed available data sources and determined that these were insufficient to reliably tell us the rate of SSI for selected orthopaedic procedures.  Therefore, to understand how we were currently performing we:

1. Created a "return to theatre" report

  • The report captures patients with a significant surgical site infection who require a return to theatre for treatment of the infection.
  • Each case identified in the report is reviewed to determine whether the additional surgery was because of infection, and if yes, whether it meets the National Health Safety Network (NHSN)[3] definition of SSI.
  • The report has been run monthly since July 2012. We also ran the report from January 2011 to June 2012 to determine a baseline and understand our performance over time.

2. Conducted a patient survey in our outpatient departmentsOutpatients Patient Survey on SSI

  • A ‘wound health questionnaire’ was developed to assess wound health after discharge.  We needed to understand how often patients go on to develop an SSI after discharge but do not re-present to the orthopaedic service.
  • These patients were thought to be treated in the community by their doctor (GP).  It was assumed that for the most part these were superficial wound infections occurring in the first 2-3 weeks after discharge from the ward.
  • The survey was given to patients between 4 and 7 weeks after their operation, at the time of their clinic appointment.  A total of 163 survey forms were completed by patients at Waitakere and North Shore Hospitals.

3. Undertook a clinical record audit

  • 99 randomly selected patient records were audited using a range of process measures to understand how we were doing according to best practice for infection prevention.
  • A small number (5) evidence-based interventions are recognised as ‘best practice’: key components of care that reduce the incidence of orthopaedic surgical site infections[4].

    These are:
    • an alcohol-containing antiseptic agent for operative skin preparation
    • preoperative bathing/showering with clorhexidine gluconate (CHG) soap
    • preoperative screening and treatment of Staphlococcus aureus (S. aureus) carriers
    • appropriate use of prophylactic antibiotics
    • appropriate hair removal
  1. The NHSN is the most widely used healthcare associated infection tracking system in the US, created by the Centers for Disease Control and Prevention (CDC).
  2. How to Guide: Project Joints. Enhanced Surgical Site Infection Prevention Bundle: Hip and Knee Arthroplasty. Institute for Healthcare Improvement. Boston. March 2012


What did we find?

  • 31 patients returned to theatre because of infection over a two year period, 2011 - 2012. The majority of these were deep tissue SSI.
  • The rate of significant infection (SSI that required additional surgery) per procedure type for the 2011 calendar year was:
    • Ankle Fracture Repair:  1.57 per 100 procedures
    • Neck of Femur Repair:  Nil SSI recorded in 2011
    • Knee Replacement:      1.64 per 100 procedures
    • Hip Replacement:          0.65 per 100 procedures
    • Of the 163 surveys returned at outpatient clinics, 7 patients had a confirmed superficial surgical site infection (a rate of 5.5 per 100 procedures). This rate is likely to be understated as there were a number of others (8) that were highly suspicious of infection but unable to be confirmed.
    • Of the 99 patients reviewed as part of the clinical record audit, 6 developed a SSI. These included 1 deep tissue infection and 5 superficial wound infections (3 hip joint and 2 knee joint replacement surgeries). Using this sample population, the rate of SSI at Waitemata DHB for hips and knee surgery is 6 per 100 procedures.

What can you do to help us?

Patients and families can help us by being involved in their care by asking the hospital staff questions such as:

At any time during your hospital stay

Ask everyone (including visitors) before they touch you or your surroundings:

Have you washed your hands?

Before a surgery

Do I need to bathe with special soap?

Do I need to be screened for skin bacteria?

Do I need to have hair removed?  If so  How will the hair be removed?

After a surgery

Am I on antibiotics?  If so  Do I still need to be on antibiotics?


What we found - clinical audit & best practice

The table below lists the information that was collected for each of the 99 patients included in the clinical record audit

Demographic Details

Procedure Details

Process Measures


  • Name
  • NHI
  • Gender
  • Ethnicity
  • DOB
  • Diabetes status
  • Smoking status
  • Weight
  • Height
  • BMI
  • MDRO status
  • Admission Date
  • Date of theatre
  • Procedure type
  • Site
  • Mode:  elective/acute
  • Surgeon
  • ASA score
  • Spacesuit use
  • Operation start time
  • Operation end time
  • Prosthesis type
  • Suture type
  • Pre-operative bathing
  • Skin prep used
  • Hair removal type
  • Antibiotic type
  • Antibiotic dose
  • Time antibiotic commenced
  • Frequency prescribed
  • Date and time of last dose
  • Lavage (wash out) of joint with antibiotic
  • Peri-operative hypoxia (low oxygen) noted
  • Dressing intact 48hrs post-operative
  • Blood sugar level 6 am post-operative day 1
  • Wound swab result if applicable

The audit provided a wealth of information about current clinical practice across the orthopaedic service. Overall current practice was aligned with best practice.  However, a number of areas for improvement were identified.

For example:

  • While there was a high level of compliance with use of prophylactic antibiotic (95% of patients within 60 mins of surgery) and consistency in antibiotic selection, there was variation in dose and frequency prescribed and no dose-adjustment for overweight/obesity.
  • Cessation of antibiotic in line with best practice was most successful when the prescriber charted a specified number of doses.
    SSI Outpatient Survey

    Antibiotic prophylaxis (prevention) could be improved by standardising the prescription and cessation orders

  • Preoperative bathing/showering, hair removal, and Staphlococcus aureus (skin bacteria) screening and treatment were generally not documented
    SSI Outpatient Survey

    Add pre-operative bathing/showering and hair removal to the preoperative checklist

Where to from here?

National SSI Surveillance Programme

In late 2012, the Health Quality and Safety Commission launched a national surgical site infection surveillance (SSIS) programme aimed at reducing SSI rates.  In December 2012, Waitemata DHB was selected as one of eight development (pilot) sites for the national programme.  The development sites have been testing and refining a standardised surveillance approach and a national reporting system using an online web tool.

The first year of the programme will focus on the surveillance of hip and knee surgeries.  A minimum data set will be submitted for every patient undergoing a hip or knee joint replacement (approximately 1,100 procedures per year at Waitemata DHB).   Patients will be followed-up for a period of 90 days following surgery. Only infections identified during a patient’s admission for surgery or during a subsequent admission will be included in the national SSI programme.  SSIs that develop after discharge but do not require re-admission to hospital will not be included in the programme.

Waitemata DHB will use the data collated from the Patient Smart SSI Rigour Project, and the data submitted to the national SSIS programme to identify further areas for practice improvement.