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Prevention of Surgical Site Infections
By Bonnie Barnard, MPH, CIC
Postoperative surgical site infections (SSIs) are still a major source of morbidity in the United States. Among the 27 million people having surgery each year, approximately 500,000 will get a nosocomial surgical site infection. Surgical site infections are the third most commonly reported nosocomial infection and are the second most commonly reported adverse event in hospitals, behind medication errors.
A 1992 analysis of these infections showed that each surgical site infection prolonged length of stay 7-9 days and resulted in an added cost of greater than $3,000 per surgical site infection.1A recent study of SSIs in orthopedic surgery concluded that SSIs prolong total hospital stays by a median of two weeks per patient, approximately double rehospitalization rates, and increase healthcare costs by more than 300 percent.1a
In another study of the health and economic impact of SSIs diagnosed after hospital discharge, researchers showed that SSIs identified after discharge had a significant impact on quality of life as measured by SF-12 scores. These patients had significantly more outpatient visits, emergency room visits, radiology services, readmissions and home health aide services than controls. Average total costs during the eight weeks after discharge were $5,155 for patients with SSI and $1,773 for controls (p<0.001).1b
Surgical site infections can be classified into incisional and organ/space manipulated during an operation. Incisional infections are further divided into superficial (skin and subcutaneous tissue) and deep (deep soft tissuemuscle and fascia). Deep incisional and organ/space are the types of surgical site infections that cause the most morbidity. Definitions of surgical site infections can be found in the Guideline for Prevention of Surgical Site Infection, 1999.2
Infections may be caused by endogenous (e.g., bacteria on the patient's skin) or exogenous sources (e.g., personnel, the environment, materials used for surgery). Most SSIs are caused by the patient's own bacterial flora. The most common microorganisms causing surgical site infection are Staphylococcus aureus (20 percent), Coagulase negative staphylococcus (14 percent) and Enterococcus (12 percent).3
Patient characteristics that put him/her at an increased risk for a surgical site infection include diabetes, nicotine use, steroid use, obesity, malnutrition, prolonged preoperative stay, preoperative nares colonization and perioperative transfusion.
Other preoperative and intraoperative risk factors for surgical site infection:
Selected Interventions Optimization of Antimicrobial Prophylaxis
One of the most important interventions in preventing surgical site infections is the optimization of antimicrobial prophylaxis. The purpose of using surgical antimicrobial prophylaxis is to provide a brief course of an antimicrobial agent in order to reduce the microbial burden of intraoperative contamination to a level that cannot overwhelm host defenses. It is not an attempt to sterilize tissues, but a critically timed adjunct to other surgical infection prevention measures.4
There are five professional organizations/references generally referred to for information on the proper type, route and timing for antimicrobial prophylaxis:
Association for Health System Pharmacists (ASHP)
The Medical Letter
Infectious Disease Society of America (IDSA)
Surgical Infection Society (SIS)
In general, the five groups agree in principle on most surgical procedures and drugs. There are some discrepancies in relation to dosing and timing, but these differences are not significant in practice.
Optimal surgical antimicrobial prophylaxis must take into consideration the following three factors:
1. Appropriate choice of antimicrobial agent
2. Proper timing of the antibimicrobial prior to the incision
3. Limiting the duration of antimicrobial administration after surgery
Appropriate Antimicrobial Agent
The choice of drug has to do with its clinical efficacy and whether it is safe, inexpensive and has a good spectrum. It should be "active against the pathogens most commonly associated with wound infections following a specific procedure and against the pathogens endogenous to the region of the body being operated on."5
For elective clean procedures using a foreign body and in clean contaminated procedures, it is generally recommended that a single dose of cephalosporin (e.g., cefazolin) be administered intravenously by anesthesia personnel in the operative suite just before the incision.
Proper Timing of Antimicrobial Administration
It is important to ensure that the antibiotic infusion is timed such that the optimal concentration is in the serum/tissue at the time of the incision. In addition, it is equally important to maintain that therapeutic level in the serum/tissue throughout the operation. Therefore, if the surgical procedure is longer than the half-life of the drug, the drug must be re-dosed during the procedure.
Historically, it was felt that the drug should be given during the interval between 30 minutes and two hours before the time of surgical incision. The most recent Medical Letter recommendations are that the drug be given no more than 30 minutes before the skin is incised.
Limiting the Duration of Antimicrobial Administration
Discontinuation of the antibiotic within 24 hours after surgery is recommended for two reasons:
1. Use of the surgical prophylaxis antimicrobial agent past this time frame has not been shown to improve surgical site infection rates and increases the cost of care unnecessarily
2. Indiscriminate use of antimicrobials can lead to the development of antibiotic-resistant microorganisms
In a prospective study of 2641 CABG patients, two outcomes were measured: (1) incidence of SSI and (2) isolation of a resistant pathogen. There was no statistical difference in SSI rates between those who got less than 48 hours of antimicrobial prophylaxis versus those who received greater than 48 hours of antimicrobial prophylaxis (8.7 percent vs. 8.8 percent; p=1.0). Furthermore, the odds of developing a resistant pathogen was 1.6 times greater (95 percent; CI 1.1- 2.6) in patients who received greater than 48 hours of antimicrobial prophylaxis after the surgery.6
The Centers for Medicare and Medicaid Services (CMS) and the Centers for Disease Control and Prevention (CDC) are co-sponsoring a national healthcare quality improvement project whose purpose is to reduce the occurrence of post-operative infection by improving the selection and timing of prophylactic antibiotic administration. The Surgical Infection Prevention (SIP) Project was rolled out via the Quality Improvement Organizations (QIOs) in each state in August 2002.
The indicators for the project are:
1. The proportion of patients who received prophylactic antibiotics within one hour before surgical incision;
2. The proportion of patients given an antibiotic consistent with current recommendations; and
3. The proportion of patients who received prophylactic antibiotics whose antibiotics were discontinued within 24 hours after surgery.
Preliminary data from the national baseline measurement for the project showed that only 47.3 percent of cases received the prophylactic antibiotic within one hour of incision, 92 percent received an antibiotic consistent with current recommendations and 41 percent of cases had antibiotics discontinued within 24 hours of the end of surgery. Obviously, there is room for improvement.
Typically, infection control professionals and surgical staff focus on measuring outcomes, i.e., surgical site infection rates. Because there are processes of care that have been shown to affect surgical site infection outcomes, this project is focused on measuring the processes of care critical to outcomes, rather than measuring the outcomes themselves. This approach is easier for several reasons. Because the focus is on process measures rather than outcome measures (SSI rates) there is no requirement for risk adjustment (as there is for surgical site infection rates, an outcome measure). In addition, relative achievable improvements in processes are generally much larger than in outcomes. And, very importantly, measuring processes can be done in rapid cycles (rapid cycle PDSA) for fast feedback and improvement.
These indicators are being monitored for the following procedures: coronary artery bypass graft; other cardiac procedures; colon; hip and knee arthroplasty; abdominal and vaginal hysterectomy; and vascular procedures. QIO staff members in each state are working with hospitals to improve these very important indicators of optimal surgical site infection prevention practices.
For more information on this project, visit www.surgicalinfectionprevention.org or contact your state's QIO. The web site has excellent information on the prevention of surgical site infections, including an annotated bibliography that is periodically updated. In addition, the project recently brought together representatives from 11 national medical organizations that write guidelines related to surgical infection prevention to explore possible areas for consensus building. The group was able to reach initial consensus clarifying areas concerning antibiotic selection, timing and duration for surgical prophylaxis for selected procedures.
What's On the Horizon?
It has been shown that proper administration of prophylactic antibiotics can decrease surgical site infections by 40 percent to 80 percent. Unfortunately, there is also evidence that even with proper antibiotic prophylaxis, in the face of breakdowns in wound management or antisepsis, patients still get wound infections. In addition, many of the risk factors for wound infection are things over which the physician has no control -- gender, age, obesity, underlying diseases, length of surgery. Now that we have learned how to minimize the chance that endogenous bacteria may cause a surgical site infection, what is next?
In a double-blind, randomized study of elective colorectal surgical procedures, all pre-, peri-, and post-operative care was standardized between a hypothermia and normothermia group. The only peri-operative difference was that the normothermia group received warmed IV fluids and forced-air cover delivered air at 40 degrees C. The researchers found that maintaining intra-operative core temperatures at normal levels was likely to decrease the incidence of surgical wound infections and shorten hospitalization.6a
Enhanced Perioperative Glucose Control in Diabetic Patients
There is now evidence to show a relationship between hyperglycemia (glucose >200) during the first 48 hours following surgery and an increased risk of surgical site infection.7 In addition, in a prospective, sequential study of 2,467 diabetic patients undergoing cardiac surgery from 1987 to 1997, those who received intermittent subcutaneous insulin had a higher rate of deep sternal surgical site infection than those who received continuous intravenous insulin during the procedure (2.0 percent vs. 0.8 percent; p = .01).8
These two studies lead us to believe that tight control of blood glucose levels in the perioperative period may lead to better surgical site infection outcomes in both diabetic and non-diabetic patients.
Supplemental Perioperative Oxygen Therapy
There is also evidence now that administration of supplemental perioperative oxygen may decrease surgical site infection rates. In a randomized controlled trial, double blinded among 500 colorectal surgery patients, those that received 80 percent inspired oxygen during and up to two hours after surgery had a lower incidence of surgical site infection than those patients who received 30 percent inspired oxygen (5.2 percent vs. 11.2 percent; p=.01).9
In a study of 2,231 CABG procedures from 1991to 1994 at a tertiary-care center, it was found that implementation of a comprehensive infection control program decreased SSIs, even after adjusting for potential confounding co-variables. The program consisted of: (1) prospective surveillance; (2) quarterly reporting of SSI rates; (3) chlorhexidene showers; (4) discontinuation of shaving; (5) administration of antibiotic prophylaxis in the holding area; (6) elimination of ice baths for cardioplegia solution; (7) limitation of operating room traffic; (8) minimization of flash sterilization and (9) elimination of postoperative tap-water wound bathing for 96 hours.10
Improvement of Outcomes
So how do hospitals improve the processes of care known to impact surgical site infection rates? The experience of the National Nosocomial Infection Study (NNIS) tells us that there are several key components to programs that have been successful in preventing nosocomial infections. In reviewing the activities of the facilities participating in the NNIS program, their staff discovered three key components of a successful prevention effort:
1. Use of a multidisciplinary team to build consensus that a problem existed, disseminate information about the infection and any planned interventions to their colleagues, and assist infection control professionals with investigations and prevention;
2. Educational sessions to introduce interventions and;
3. Data dissemination to show the impact of the interventions.
They emphasized the importance of sharing success stories and outlining epidemiologic approaches to understanding and describing best practices.11 This sharing can be between facilities or among staff within your own facility. Just remember that it is the people working at the point-of-care that have the most to contribute to any improvement process and it is important to get them involved.
Staying focused on the measurement and improvement of the processes of care that have been shown to directly impact surgical site infections while using outcome measures as "stepping stones" will ensure a surgical site infection prevention program that will succeed.
Bonnie M. Barnard, MPH, CIC, is an infection control professional with 18 years of experience in hospitals, long-term care and the outpatient setting. She has been certified in infection control since 1984. She has published and presented abstracts on many subjects related to infection control.
|Type of Procedure||CABG||Colorectal||THR||TKR|
|Total Cost (millions)||$83.5||$127||$196||$63|
1. Understand and describe the prevalence of surgical site infections.
2. Describe the causes of SSIs.
3. Describe the methods of preventing SSIs.
|TEST QUESTIONS: TRUE OR FALSE||T||F|
|1. Most surgical site infections (SSIs) are caused by exogenous sources of bacteria.|
|2. The purpose of using surgical antimicrobial prophylaxis is to reduce the microbial burden of intraoperative contamination.|
|3. Optimal surgical prophylaxis must take into consideration whether or not the patient wants to receive the antibiotic.|
|4. Ideally, surgical prophylactic antibiotics should be timed such that the optimal concentration is in the serum/tissue at the time of the incision.|
|5. A single dose of cephalosporin is generally considered to be a good choice of drug for elective clean procedures.|
|6. Continuing the surgical prophylaxis antimicrobial agent past 24 hours after surgery has not been shown to improve SSI rates.|
|7. The national Surgical Infection Prevention Project is focused on ensuring that all surgical patients have appropriate preoperative teaching.|
|8. Measuring processes can be done in rapid cycles for fast feedback and improvement.|
|9. Tight control of perioperative blood glucose levels may lead to better SSI outcomes.|
|10. According to the NNIS program, patient involvement is one of the three key components of a successful SSI prevention effort.|