In a thorough review of the literature on surgical site infections, this author shares insights on key risk factors, discusses current concepts and controversies with preventative measures, and offers a salient overview on common pathogens.
Numerous studies have demonstrated that postoperative infections following elective, clean foot and ankle surgery are relatively uncommon. Indeed, a review of the recent literature from the Centers for Disease Control and Prevention (CDC) shows the surgical site infection (SSI) rate to be approximately 2.1 percent for these types of surgical procedures.1 However low the relative incidence may be for the development of postoperative infection following lower extremity surgery, the management of these types of complications can present a challenge to every surgeon. The presence of postoperative wound infections often delays the recovery of surgical patients and these complications commonly increase the length of stay in the inpatient setting.2,3
Furthermore, surgical site infections may produce long-lasting sequelae that can require additional medical and surgical management as well as further nursing care. This creates both a psychological drain on the patient as well as a financial drain on an already besieged healthcare system.4 Consequently, the effective diagnosis, management and ultimate prevention of surgical site infections are relevant to providing quality patient care in an ever evolving healthcare environment.
Various studies demonstrate that a reduction in surgical site infections is directly related to increased education (for the surgeon, the operating room team and the patient) and awareness of the causes and risk factors for the development of postoperative infections. A critical evaluation of infection control practices has furthermore shown a reduction in postoperative infection rate, particularly in those instances in which regular feedback is provided to the surgeon following surveillance for wound infection.1 It is important to note, however, that simple surveillance is not adequate to provide essential reductions in infection propagation. Action and prevention are key, and appropriate prevention of surgical site infection begins prior to the surgical encounter.
There are numerous risk factors that can predispose one to the development of surgical site infections. These risk factors have been validated and documented in the literature, and they combine to provide the relative risk for the development of postoperative infections. It is important for the surgeon to recognize the potential risk factors in his or her surgical patients, and subsequently initiate the chain of action that can attempt to prevent or at least minimize the potential for the development of surgical site infections.
These factors can be divided into essentially two categories, intrinsic and extrinsic factors. Intrinsic factors are those factors related to the patient and to the surgical procedure being performed. Patient-related risk factors include the patient’s age, the presenting condition, the potential for concomitant disease, preexisting infection, tobacco usage, malnutrition, obesity and uncontrolled diabetes. These are all independent risk factors for developing a postoperative infection.5-7
Sorenson and colleagues found the optimal abstinence period required in heavy smokers to reduce the risk of surgical site infections was four weeks.8 Malnutrition lowers a host’s defenses and compromises the immune system, thus predisposing the patient to infection and poor wound healing.9 Recognizing at-risk patients prior to surgery is essential to successful management of these complicated patients during the perioperative period.
As I noted above, the presence of diabetes is an independent risk factor for the development of surgical site infections. As the epidemic of diabetes increases, there has been increasing interest in various surgical techniques for the treatment of the diabetic foot. Armstrong and colleagues developed and later validated a diabetic foot surgery classification system designed to assist the surgeon in assessing risk when determining a rationale for foot and ankle surgery in this high-risk population.10,11 This system included class 1 (elective), class 2 (prophylactic), class 3 (curative) and class 4 (emergency) surgery. There is an increase in postoperative infection with each increasing class of foot surgery.11
There are risk factors associated with the procedures surgeons are performing as well. It is a reality that certain types of procedures are simply more prone to the development of surgical site infections. Infection rates increase in complicated reconstructive surgery, types of diabetic foot surgery, open fractures and traumatic wounds.12-16 Additional surgical procedure-related risk factors include poor surgical technique, the duration of operation, the use of drains (closed drain systems reportedly reduce the risk of surgical site infections), hematoma formation, excessive use of electrocautery and accidental cross contamination, commonly either from bowel or infected tissue.17 Furthermore, researchers have demonstrated that inappropriate antibiotic prophylaxis and inadequate skin prep prior to surgery increase the risk of the development of postoperative infection, especially in high-risk surgical patients, immunocompromised patients, those living with diabetes, and patients suffering from vascular disease.18,19
Extrinsic risk factors are those factors associated with the operating room, the operative equipment and all potential factors that are not directly related to the patient or the surgical procedure. The literature has demonstrated that these factors, in combination with intrinsic factors, can often contribute to the development of postoperative wound infections.20 These factors include the number of individuals in the operating room, inadequate sterilization/disinfection of surgical equipment, reuse of inadequately sterilized invasive devices, prolonged preoperative stay, inappropriate dressing techniques and the length of the surgical procedure. Prolonged surgical time increases the risk for surgical site infections and extended tourniquet time may cause tissue ischemia that enhances infection. With every hour of operating time, the infection rate doubles.21
It is said that an “ounce of prevention is worth a pound of cure.” This is especially the case with the development of surgical site infections. Researchers have shown that preventative measures significantly reduce the risk for the development of surgical site infections in numerous patient populations.22-28 Preventative measures, such as prophylactic antibiotics and the use of skin preparations prior to incision, are geared to address extrinsic risk factors, most commonly those risk factors associated with surgical procedure. One can also attempt to address intrinsic patient factors such as tobacco usage via smoking cessation modalities. In those patients with concomitant medical issues, a delay of elective surgery until the patient has greater medical management can further reduce the risk of surgical site infections.
While it is common to use antibiotic prophylaxis in foot and ankle surgery to reduce the incidence of surgical site infections, the use of antibiotics is controversial.22 Historically, surgeons have utilized antibiotic prophylaxis in four different scenarios: 1) when incorporating implantable devices (these implanted devices often lower the bacterial burden necessary to cause wound infection); 2) in cases of trauma or limb salvage; 3) in cases involving prolonged operating time (greater than two hours); and 4) in cases involving immunocompromised patients.22,23
Most would agree that the use of perioperative antibiotic therapy is indicated for dirty or contaminated wounds, and for those procedures known to carry a greater risk of the potential for the development of surgical site infections, including those procedures in which surgeons are utilizing hardware or implants.23
The Infectious Diseases Society of America (IDSA) maintains evidence-based guidelines for antimicrobial prophylaxsis in surgery. There are regular updates to these guidelines, which can provide the clinician with vital information about the drug, dose and timing for effective perioperative reduction of surgical site infections.24
However, the use of prophylactic antibiotics remains a controversial issue in clean, elective foot and ankle surgery. Indeed, one must realize that the use of preoperative antibiotics may not always be necessary for ensuring successful outcomes. Surgeons should avoid the careless use of antibiotics. Current recommendations for regarding prophylactic antibiotic usage indicate that following appropriate antibiotic selection, the patient should receive the relevant antibiotic within 60 minutes of surgery and antibiosis should not be continued more than 24 hours following surgery.24
Surgeons may also deliver antibiotics locally with the use of antibiotic impregnated beads. Generally, the beads are infused with an aminoglycoside, such as gentamicin or vancomycin, because these agents are active against the most common pathogens and offer heat-stable properties.25 These beads deliver high levels of the antibiotic locally with little systemic uptake and systemic toxicity is not a concern. Many authors have advocated the benefits of antibiotic beads in foot and ankle surgery.26,29
In addition to the use of preoperative antibiotics and antibiotic beads intraoperatively, perioperative patient care has further evolved to reduce the risk of surgical site infections. Among these functions, preoperative preparation of the surgical area reportedly lowers the rate of postoperative infection.27-28 To prepare the skin, shaving is no longer recommended. When necessary, one can remove hair with clippers. Shaving leaves the skin with the potential for small lacerations, which can increase the risk of colonization and subsequent infection postoperatively.27
Researchers have also demonstrated that preoperative skin preparation reduces the incidence of surgical site infections.28 Physicians should ensure preoperative skin antisepsis for the patient in order to reduce the risk of postoperative infection. The operation site must be well disinfected before incision. Alcoholic solutions containing long-acting skin disinfectants, such as chlorhexidine or povidone iodine, are preferred in this application.28 The use of such disinfectants with greater than 40% alcohol content, however, increases the risk of burns to the patient during diathermy.30 Bibbo and colleagues demonstrated in a prospective randomized study that chlorhexidine and alcohol were superior to povidone iodine solution in foot and ankle surgery.31 One should apply the antiseptic with friction well beyond the operation site as part of the standard preparation prior to incision, and one should allow the area to dry before operating.
In conjunction with preparation of the surgical site, it is necessary that the surgeon prepare as well. The antiseptic utilized for the surgical scrub is also vitally important in the reduction of surgical site infections. Recent studies have shown that a scrub-less aqueous alcohol hand rub is as effective as povidone iodine and chlorhexidine gluconate scrub.32 A scrub-less technique may improve surgeon adherence and enhance the overall effectiveness of the surgeon’s preoperative scrub. If the surgeon prefers a more traditional scrub, the scrub should last at least two minutes as this is the minimum time required for iodine to be effective.
Researchers have also identified operating room ventilation as a potential source for the development of surgical site infections. Therefore, in high-risk cases, such as cases involving implantation of total joints, laminar flow systems (airflow 0.5 m/s) that deliver about 300 air changes per hour can be helpful in maintaining positive pressure.33
Common pathogens for surgical site infections vary somewhat based upon the nature of the procedure one is performing. In those instances of surgical site infections following clean orthopedic procedures, normal skin flora pathogens, such as Staphylococcus aureus and Streptococcus, are the most common offending organisms.19,34-36 Surgical site infections following other types of surgery can demonstrate more of a polymicrobial environment at the infection site. Virulence and pathogenicity are major factors in the development of infection. Different bacteria are known to be more or less invasive, and it is these properties that will make them more likely to be the underlying pathogen in a surgical site infection.
Furthermore, the emerging number of multidrug-resistant strains of bacteria has made the management of surgical site infections increasingly difficult, and the consequences for untreated or undertreated surgical site infections can be devastating. It is important that clinicians appropriately recognize those patients who are at-risk to potentially reduce the incidence of multi-drug resistant, infection-related morbidities. The risk factors for methicillin resistant Staphylococcus aureus (MRSA) infections include recent previous hospitalization, nursing home residence, prior antibiotic usage and intravenous drug use.37,38 The most important risk factor, however, is a previous history of MRSA infection and one should obtain a thorough patient history as part of the preoperative workup to assess for potential MRSA risk factors.38
Prevention of surgical site infections requires proper patient selection, meticulous surgical technique, a clean surgical environment, appropriate antibiotic prophylaxis (when indicated) and antisepsis at the surgical site. When surgical site infections occur, early and aggressive management is key.
Perioperatively, each surgeon must thoroughly evaluate his or her surgical patients, and identify those intrinsic and extrinsic risk factors that can predispose a patient to subsequent surgical infection. It is incumbent upon each member of the surgical team to practice appropriate hand hygiene in the perioperative setting, and it is the surgeon’s responsibility to enforce strict sterile principles by the entire surgical staff. The literature is quite clear. The implementation of evidence-based practices during the perioperative phase reduces the risk of surgical site infections, lowers healthcare costs and, most importantly, improves patient outcomes that will save limbs and lives.
Dr. Fitzgerald is an Assistant Professor of Surgery at the University of South Carolina School of Medicine — Greenville in Greenville, S.C. He is also affiliated with the Center for Amputation Prevention with the Greenville Health System in Greenville, S.C. Dr. Fitzgerald is a Fellow of the American College of Foot and Ankle Surgeons.
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