How To Prevent Postoperative Infection
Postoperative infection following elective, clean foot and ankle surgery is relatively uncommon. The Centers for Disease Control and Prevention (CDC) reports the surgical site infection (SSI) rate to be 2.1 percent for clean, uncontaminated surgery.1 However, when postoperative infection does occur, it may affect functional outcomes and the patient’s quality of life.
The incidence of infection varies from one surgical procedure to another and from patient to patient.2 Infection rates increase in complicated reconstructive surgery, types of diabetic foot surgery, open fractures and traumatic wounds.3-5 There are a few critical factors to consider when discussing SSIs and they include patient factors, pathogen factors, surgeon factors and environmental factors. Accordingly, it is important to have a strong understanding of these key factors as well as a solid grasp of techniques to help reduce the risk of postoperative infections.
There are many host factors that may potentially heighten the risk of postoperative infections.
Malnutrition, advanced age, obesity, smoking and uncontrolled diabetes are all independent risk factors for developing a postoperative infection. Malnutrition lowers host defenses and compromises the immune system, thus predisposing the patient to infection. Older patients generally have many comorbidities and researchers have shown that increased age is a factor for increased risk of postoperative SSIs.6
Research has shown that smoking significantly increases the risk of SSIs. Sorenson, et al., found the optimal abstinence period required in heavy smokers to reduce the risk of SSIs was four weeks.7 The physician should counsel patients and offer cessation treatment during the preoperative phase.
People with uncontrolled diabetes are at increased risk for SSI. Hyperglycemia negatively affects neutrophilic responses to infection and studies have shown that perioperative plasma glucose levels above 220 mg/dl increase the risk of surgical site infections.8,9 One should monitor these patients closely for glycemic control. At times, these at-risk patients may present with an ulceration preoperatively, complicating the matter even further.
Any systemic disease that compromises the host defense against a pathogen will place an individual at risk for a SSI. Recognizing at-risk patients before embarking on surgery is paramount to successful management during the perioperative period.
Recently, there has been increasing interest in various surgical techniques for the treatment of the diabetic foot. With this in mind, researchers proposed and later validated a diabetic foot surgery classification system.4,10
This classification system was designed to assist the surgeon in assessing risk when determining a rationale for foot and ankle surgery in this high-risk population. 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.4
What You Should Be Aware Of With Open Fractures
Open fractures carry a greater risk for infection and are considered contaminated. In these cases, antibiotic use is deemed therapeutic as opposed to prophylactic.5 Early antibiotic therapy is critical to achieving successful outcome in these patients. Physicians should direct antibiotic selection toward aerobic gram-positive cocci and increased gram-negative coverage for type II and type III fractures. Patzakis and Wilkins found that the administration of preoperative antibiotics was the most important factor in determining the rate of postoperative infection in open fractures.11
Also vital in the treatment of open fractures are adequate debridement, copious irrigation and skeletal stabilization. Strict adherence to these basic principles and guidelines can reduce the risk of complications and prevent damaging postoperative infections.
A Closer Look At Common Pathogens
The bacterial properties of virulence and pathogenicity are important factors in infection. Some organisms are more invasive and likely to cause an infection, and some are more resistant to antibiotics. When it comes to clean orthopedic procedures, Staphylococcus aureus (from the exogenous environment or the patient’s skin flora) and Streptococcus are the most common organisms.12,13
The emergence of multi-drug resistance is a major concern and can have devastating effects. Recognizing at-risk patients can potentially reduce the incidence of multi-drug resistant infection related morbidities. Risk factors for methicillin resistant Staphylococcus aureus (MRSA) infections include recent previous hospitalization, nursing home residence, prior antibiotic usage and intravenous drug use. However, perhaps the most important risk factor is a previous history of MRSA infection/colonization.14-19 The surgeon should obtain a thorough patient history to detect potential risk factors for MRSA.
Ensuring Key Aspects Of Sterile Procedures And Preparation
The surgeon must adhere to strict sterile principles throughout the entire procedure. Meticulous surgical technique, avoidance of rough tissue handling and judicious use of cautery are essential to avoid the creation of an environment for bacteria to thrive. The surgeon must also avoid extensive tissue dissection and appropriately manage dead space to prevent the formation of a postoperative hematoma, which increases the risk of infection. Prolonged surgical time increases the risk for SSIs and extended tourniquet time may cause tissue ischemia that enhances infection. With every hour of operating time, the infection rate doubles.6
Also keep in mind that studies have shown the use of supplemental oxygen and the regulation of core temperature during the perioperative period reduce the risk of surgical wound infection.13,20
Often, surgeons overlook the operating room itself as a potential source of contamination. Increased traffic in and out of the operating room increases airborne bacteria. Restricting the number of people coming in and out of the operating room is recommended.21 Appropriate air handling systems with the use of newer, advanced systems and adequate disinfection of operating room surfaces between cases are important in limiting the microorganisms in the environment. Surgeons must pay strict attention to proper equipment sterilization techniques to limit contamination by microorganisms.
The initial steps in preventing postoperative SSIs begin with proper surgical preparation for both the surgeon and the patient. Removal of hair from the surgical site does not offer an advantage in the prevention of SSIs. However, if the surgeon prefers the site to be free of hair, using clippers or depilatory creams as opposed to razors may decrease the risk of SSIs significantly. It is best to perform this hair removal at the time of surgery.22
Physicians should ensure preoperative skin antisepsis for the patient in order to reduce the risk of postoperative infections. Researchers have performed comparisons of different solutions including chlorhexidine gluconate, alcohol or povidone iodine. In a prospective randomized study, Bibbo, et al., found that chlorhexidine and alcohol were superior to povidone iodine solution in foot and ankle surgery.23
Draping is important for maintenance of a sterile field and should ideally be impermeable. Adhesive plastic iodine-impregnated drapes do not decrease the risk of SSIs and may actually increase the risk of developing a postoperative infection.24 While researchers have recommended covering the forefoot and toes with a drape or glove to reduce the risk of contamination of the surgical site, this practice does not decrease the risk of postoperative infection.25
It is also important to use an appropriate antiseptic for the surgical scrub. Recent studies have shown that a scrub-less aqueous alcohol hand rub is as effective as povidone iodine and chlorhexidine gluconate scrub. A scrub-less technique may improve surgeon compliance and enhance its effectiveness. 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.13
What The Literature Reveals About Antibiotic Prophylaxis
The use of prophylaxis antibiotics in foot and ankle surgery remains controversial. Miller reported a postoperative infection rate of 2.2 percent in 1,841 patients after clean, elective foot and ankle surgery without any prophylactic antibiotics.26 Zgonis, et al., retrospectively reviewed 555 charts of patients who received elective foot and ankle surgeries. Three hundred six patients received prophylactic antibiotics and eight of these patients (1.4 percent) acquired a postoperative infection. In contrast, 249 patients did not receive preoperative antibiotics and nine of these patients (1.6 percent) acquired a postoperative infection.
In this review, patients receiving preoperative antibiotics underwent more complex procedures and there was more frequent use of internal and external fixation. However, out of the patients with multiple surgeries and among the patients receiving internal and external fixation, the use of preoperative antibiotics had no effect on the incidence of SSIs. The authors concluded that prophylactic antibiotic therapy is not necessary in clean, elective foot and ankle procedures.21
Traditionally, surgeons utilize antibiotic prophylaxis in four different scenarios:
• when incorporating an implantable device (screw, plates, replacement joint, etc.);
• in cases of trauma or limb salvage;
• in cases involving prolonged operating time (less than two hours); and
• in cases involving immunocompromised patients.12
The selection of an appropriate antibiotic requires a thorough understanding of the susceptibility of the suspected organism, and the activity and safety profile of the selected drug. One must direct the antibiotic against the most expected pathogen found if an infection occurs. In situations in which a prophylactic antibiotic is warranted, cephalosporins such as cefazolin or cefuroxime are the drugs of choice.12,13,27 In patients with a b-lactam allergy, clindamycin and vancomycin are common alternatives.
In patients with known risk factors for MRSA or in facilities with recent outbreaks of MRSA, one may use vancomycin. However, surgeons should take caution against the reckless use of vancomycin and other anti-MRSA drugs as bacterial resistance will continue to rise.
Key Insights On Antibiotic Dosage And Timing
The correct dosage and timing of administration of the antibiotic is important in helping to decrease SSIs. Often, physicians use incorrect dosing for obese patients. If a patient weighs > 80 kg, one should double the dose of cefazolin (2 g) and give a higher dosage (900 mg) of clindamycin.12,13,27 Surgeons must also take into account the duration of the surgical case. If the procedure is longer (greater than one to two times the half-life of the antibiotic), re-administration of the antibiotic is recommended.12,13,27
Proper timing of antibiotic administration is essential in reducing the risk for postoperative infections. The desired effect is to have peak levels of antibiotics in the tissue while the surgical site is exposed to open air. Therefore, administration of the antibiotic should be as close to the initial incision as possible.12,13 Many organizations, including the American Academy of Orthopaedic Surgeons (AAOS), have recommended administration of intravenous antibiotics within 60 minutes of the start of the surgical procedure. Vancomycin is the exception as the AAOS recommends giving this agent within 120 minutes prior to surgery to prevent an inflammatory reaction.27
In clean foot and ankle surgery, patients should discontinue all prophylactic antibiotics within 24 hours of the procedure.12,13,27 There is no data supporting prolonged antibiotic use to decrease SSIs. On the other hand, prolonged antibiotics increases the risk of resistant bacteria and increases healthcare costs.12,13,27
Surgeons may also deliver antibiotics locally with the use of antibiotic impregnated beads. Generally, the beads are infused with an aminoglycoside, such as gentamycin or vancomycin, because these agents are active against the most common pathogens and offer heat stable properties.13 These beads deliver high levels of the antibiotic locally with little systemic uptake and systemic toxicity is not a concern.28 Many retrospective reviews have suggested the benefits of antibiotic beads in foot and ankle surgery.13
Pertinent Pointers On Minimizing Infection Risk
Lavage is an effective intraoperative technique to decrease the incidence of SSIs. The mechanical effect of the lavage in removing necrotic tissue, bacteria and debris from the surgical site is more important than the contents of the fluid. Authors have shown that high pressure lavage is more effective than low pressure lavage for the removal of debris.13
Surgeons often employ drains to manage dead space and prevent the formation of postoperative hematoma. Simple conduit drains are not recommended as they increase the retrograde migration of bacteria into the wound.29 There is no evidence showing that the use of a postoperative surgical drain prevents the formation of SSIs, wound dehiscence or hematoma formation.30 However, we frequently use closed suction surgical drains to manage dead space. Prompt removal of the drain will help decrease the risk of a SSI.
The surgical dressing may assist in facilitating wound healing and preventing SSIs. Dressings increase reepithelialization by two to six times due to their occlusive nature and proliferation of the fibroblasts, and angiogenesis occurs in response to the local hypoxic environment. Surgical dressings act as barriers to bacteria. Researchers have recommended using three layers of surgical dressings.31 The first layer should be a non-adherent dressing such as Xeroform, Adaptic or Mepitel. The second dressing should be an absorptive layer such as gauze, Kerlix or cast padding. The final layer should provide compression and immobilization. Accordingly, one may use an ACE bandage or coban.
The prevention of infection, through proper patient selection and meticulous surgical technique, is essential to satisfactory outcomes. The surgeon must thoroughly evaluate the medical condition of the patient and identify potential risk factors for infection. He or she must enforce strict sterile principles by the entire surgical staff. 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. Future prospective randomized studies are necessary to evaluate the effectiveness of preoperative antibiotic use. The implementation of evidence-based practices during the perioperative phase reduces the risk of surgical site infections, lowers healthcare costs and, most importantly, improves outcomes.
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