Surgical site infections (SSIs) can pose a significant challenge to patient outcomes. With this in mind, these authors discuss the incidence of these infections, pertinent considerations with preoperative patient assessment and key factors in deciding on the proper timing, type and use of antibiotic prophylaxis in the perioperative setting.
According to a 2017 study by the Centers for Disease Control and Prevention (CDC), approximately 80 million surgical procedures are performed each year in the United States alone with 46 million being inpatient procedures and 34 million being outpatient/ambulatory procedures.1-6 Orthopedic procedures account for one of the most common categories of surgery. The most recent National Ambulatory Medical Care Survey (NAMCS) revealed that in 2010, 63 million visits were made to physicians specializing in orthopedic surgery.6 This number represents a 14 million increase from a 2009 survey estimating 49 million orthopedic surgery visits.3,6
The U.S. Department of Health and Human Services’ Agency for Healthcare Research and Quality (AHRQ) and the CDC both state that surgical site infections (SSIs) occur in 1.9 to four percent of all patients, and are a significant cause of postoperative morbidity and mortality as up to three percent of patients with an SSI will die from the SSI.1,2,7 The average extra inpatient stay for a patient that developed an infection post-surgery was six and a half days.8
For foot and ankle surgeries specifically, international studies from the United Kingdom and Australia have found the incidence of SSIs to range from 0.26 percent to five percent.7,9 In a clinical audit report of close to 3,000 surgical procedures and 2,250 fixation devices, Maher and Wilkinson noted a suspected infection rate of 2.44 percent and a proven rate of 0.42 percent.10 Furthermore, patients who do not receive appropriate perioperative antibiotics are 2.32 times more likely to acquire an SSI in comparison to those who do receive appropriate antibiotics.11 Almost a quarter, 24.3 percent specifically, of health care-associated infections (HAI) are SSIs.12
A surgical site infection is defined by the Agency for Healthcare Research and Quality as infection related to an operative procedure that occurs at/or near the surgical incision site within 30 days of the procedure or within 90 days to a year of prosthetic material implantation during surgery.13,14 The patient with a SSI also presents with purulent drainage from the incision, organisms isolated from a culture of fluid or tissue, or an incision deliberately opened by the surgeon when the patient has signs or symptoms of an infection.13 Along with the associated discomfort or pain and a decrease in the quality of surgical outcomes, there is a concomitant increase in the cost of health care. The estimated cost ranges from $10,443 for minor infections to $90,000 or more with a prosthetic joint implant or antimicrobial-resistant infections.2,7,9
Surgical site infections are significant from the perspectives of quality of life and socioeconomics. However, there is little published research on SSIs, especially in the foot and ankle surgery realm. Physicians, hospitals and organizations have not come to a consensus on general guidelines or algorithms on the use of prophylaxis in elective foot and ankle surgery. Heterogeneous studies with variable research methodologies, patient selection, procedure techniques and local policies have led to these discrepancies. Some have questioned whether the risk of potential side effects or increase in microbe resistance outweighs the benefit of prophylactic antibiotic use given the relatively low incidence of SSIs.
With these points in mind, let us review the currently available research on the use of antibiotic prophylaxis in elective surgery.
Preoperative Risk Assessment For Surgical Site infections: What You Need To Know
When thinking about antibiotic prophylaxis, one should first consider patient and procedural factors. If contraindications arise, surgeons should consider patient factors over procedural factors in driving the decision to use antibiotic prophylaxis.15
The CDC SSI risk assessment is based on the American Society of Anesthesiologists (ASA) Physical Status (PS) Classification System score, which reflects the patient’s state of health prior to the procedure, the surgical wound classification that reflects its state of contamination and the duration of the operation that reflects the technical aspects of the procedure.7 The ASA PS Classification score takes into account patient factors including but not limited to smoking, alcohol, pregnancy, obesity, diabetes, hypertension, hemostasis and lung disease. An ASA score of greater than II denotes increased risk for infection as the patient is considered to have at least mild systemic disease.
As part of the CDC SSI risk assessment, one can classify wounds into four categories: Type I or clean, Type II or clean-contaminated, Type III or contaminated, and Type IV or dirty/infected (see “A Guideline For Classifying Surgical Wounds” below). Numerous national organizations including the Society for Healthcare Epidemiology of America (SHEA), the Infectious Diseases Society of America (IDSA), the Surgical Infection Society (SIS) and the American Society of Health-System Pharmacists (ASHP) concur with the CDC’s SSI risk assessment.9,16,17
In addition to the ASA PS Classification score, surgical wound classification and procedure duration, one must also consider tourniquet use and the type of surgery as it relates to foot and ankle surgery. This protocol is in agreement with multiple high-level studies and national health organization recommendations to adequately determine the risk for an SSI upon initial preoperative patient assessment. As a general rule of thumb, antimicrobial prophylaxis is recommended when the patient is immunocompromised, has a history of infection at the site of surgery or for surgeries of prolonged duration lasting more than three hours.7,15
What Studies Show About The Roles Of Skin Preparation And Sterile Technique In Preventing SSIs
After the risk assessment but prior to the initial surgical incision, the surgeon or surgical team prepares the patient’s skin. Skin preparation and sterile technique alone can be very impactful in preventing SSIs. Appropriate skin preparation includes methicillin-resistant Staphylococcus aureus (MRSA) decolonization, appropriate hair removal and skin antiseptic.18 Both skin preparation and sterile technique should be standards of care in an operating room.
Murray and coworkers found the combination of a two percent chlorhexidine cloth wash with traditional soap and water shower prior to shoulder surgery versus soap and water shower alone was associated with a threefold reduction of colony count for coagulase-negative Staphylococcus, a decrease in the rate of positive culture for coagulase-negative Staphylococcus and Corynebacterium, and a decrease in overall bacterial burden.19 One could also ensure MRSA screening prior to surgery and if the patient is positive for MRSA, the surgeon can follow the guidelines discussed below. Dunn and colleagues evaluated the current evidence regarding routine antibiotic prophylaxis in hand surgery and found that sterile prepping and draping techniques were more pertinent than antibiotic prophylaxis in clean hand surgery with fewer adverse effects.20
Determining Antibiotic Selection, Timing and Dosage For Surgical Prophylaxis
In clean foot and ankle procedures without the involvement of foreign materials, there is no evidence for antibiotic prophylaxis. However, there is evidence supporting antibiotic prophylaxis when implanting internal fixation devices and joint replacements.9,15-17,21 Determination of the appropriate prophylactic antibiotic requires antimicrobial stewardship to reduce the use of inappropriate antimicrobials, minimize microbial resistance, improve patient outcomes and decrease the spread of infections caused by drug-resistant organisms.20-25
In a retrospective study involving 555 patients, Zgonis and colleagues noted penicillin resistance in all patients who had preoperative prophylaxis and a postoperative infection.22 In patients without a resistant infection history, Dayton and colleagues recommend use of narrow-spectrum antibiotics that act against Staphylococcus aureus for prophylaxis.15 In order to use narrow-spectrum agents, we must identify common bacteria in foot and ankle surgery. Gram-negative and gram-positive Staphylococcus are very common bacterial isolates found in foot and ankle surgeries.20 Researchers have identified Staphylococcus aureus, Staphylococcus epidermidis, aerobic streptococci and anaerobic cocci as prominent microbes in SSIs.18,26
Additionally, when it comes to infections of foreign material, due to the propensity to form biofilms, Staphylococcus aureus and Staphylococcus epidermidis were common among foot and ankle SSIs.20,26-28 Staphylococcus aureus, gram-negative bacilli, coagulase-negative staphylococci, and beta-hemolytic streptococci are reportedly common in orthopedic procedures, and Deny and colleagues noted the presence of Staphylococcus aureus and Staphylococcus epidermidis on the surfaces of devices surgeons used for arthroplasty.26
Based on the above study findings, the use of cefazolin is generally indicated. For gram-negative bacteria, vancomycin or clindamycin is indicated with cefazolin for patients without beta-lactam allergies.25 For patients with beta-lactam allergies that involve a gram-negative bacterium, clinicians can utilize vancomycin or clindamycin with aztreonam, gentamicin or a single dose of a fluoroquinolone such as ciprofloxacin, levofloxacin or moxifloxacin.26 Adult dosing, pediatric dosing, half-life, side effects and cultural sensitivity for each of the aforementioned medications are summarized in the table “Current Insights On Antibiotic Dosing For Surgical Prophylaxis” below.
If MRSA colonization is documented, vancomycin is indicated at the time of surgery with two percent mupirocin prescribed twice daily intranasally for five days prior to surgery, or five percent povidone-iodine solution intranasally for 10 seconds to one hour prior to surgery. To the best of our knowledge, there is no reported incidence of anaphylaxis, toxicity or other adverse drug events and/or serious side effects related to the use of prophylactic antibiotics in foot and ankle surgery. As long as physicians administer the recommended or adjusted doses depending on the patient’s needs, there have been no serious complications. This may also be due to the limited duration of antimicrobial exposure in surgical prophylaxis.
There are no high-level evidence studies in foot and ankle surgery regarding dosing but general guideline statements have been published. Related studies have shown that a bolus dose of antibiotics prevents SSI in bone and joint surgery.7,9 For procedures lasting more than two half-lives of the antibiotic, consider redosing.16 It is recommended that a surgeon repeat the intraoperative dosing for a surgical duration of greater than four hours or if there is a greater than a 1500 mL loss of blood.18 Further studies are necessary, specifically in foot and ankle surgery, to draw stronger conclusions for podiatric surgery practice.
Current studies also use a parental route of delivery rather than intramuscular or oral delivery. This could be due to the hepatic first pass for some oral medications, hence taking longer to reach a minimum inhibitory concentration of 90 (MIC90). However, Yoda and coworkers found the oral route was as effective as parental for mandible surgery.27 When considering preoperative antimicrobial use, it is critical that one give the prophylactic antibiotic adequate time to reach MIC90 as well as provide adequate patient protection once the surgery has concluded.
Multiple researchers have recommended administration of the preoperative antibiotic dose 60 minutes prior to the first surgical incision.15-18,26 Specifically, when it comes to fluoroquinolones and vancomycin, patients should receive these antibiotics 120 minutes prior to the first surgical incision.15-18,26 Researchers suggest discontinuing antibiotics 24 hours after surgery.15,26 If a patient was already taking antibiotics prior to surgery, it is best to re-dose 60 minutes prior to the first incision.18
Considering The Effects Of Tourniquet Application On Antibiotic Availability
Many foot and ankle surgeons implement the use of a tourniquet. However, keep in mind that the timing of tourniquet inflation affects plasma concentration of antibiotic medication as limb ischemia may diminish MIC90 at the operative site.9 Accordingly, one should administer antibiotic prophylaxis prior to inflation of the tourniquet.15 Quantitative timing of tourniquet inflation and plasma concentration of the antibiotic prophylaxis seem to have a correlation, which could affect SSI rates.
In one interesting study, Akinyoola and colleagues showed that antimicrobial prophylaxis administered five minutes prior to tourniquet inflation resulted in an SSI rate of 14.8 percent while antimicrobial prophylaxis given one minute prior to tourniquet inflation resulted in an SSI rate of 3.9 percent.28 It is important to note that this study primarily involved trauma surgeries and this could affect the results. The required antibiotic concentration to achieve MIC90 is approximately 0.5-1.0 μg/g.29,30 Studies by Deacon and colleagues and Dounis and team showed that antimicrobial prophylaxis administered 60 minutes prior to tourniquet inflation lead to plasma concentration levels two to four times what is necessary at 2.39 ± 1.19 μg/g.29,30 However, the study by Dounis and team focused exclusively on cephalosporins.30
While recommendations can be postulated based on the above studies, there is a need for more focused research in the future in order to draw stronger conclusions on the effect of tourniquet application to MIC90 and the combined effect on SSIs.
Unique Considerations In Foot And Ankle Surgery
In terms of the types or categories of procedure in which antibiotic prophylaxis is indicated, the international podiatric surgery community is at a partial agreement with some notable differences. The international podiatric community is in general agreement that antibiotic prophylaxis is not indicated for clean procedures that do not require internal fixation, foreign materials or implants.15,19,26
When looking at uncomplicated or uninfected bone and joint procedures, the U.K.-based College of Podiatry’s Podiatric Surgery and Clinical Outcome Measurement (PASCOM–10) suggests that even with internal fixation, antibiotic prophylaxis is not needed.7,9 The PASCOM-10 recommendation is in agreement with Cooney and Kumar, who studied hallux valgus surgeries specifically and did not find a need for antibiotic prophylaxis.9,31
Conversely, multiple consensus studies suggest a need for antibiotic prophylaxis in all bone and joint surgeries, and that SSIs would be significantly reduced by their use.16,32 Both the Scottish Intercollegiate Guidelines Network (SIGN) and the National Institute for Health and Clinical Excellence (NICE) recommend the use of prophylaxis in clean orthopedic surgery involving an implant.17,21
Other studies have noted a lack of evidence to determine whether or not surgeries with fixation devices require antibiotic prophylaxis, recommending that the surgeon should decide based on the circumstances and, if there are doubts, to use hospital as well as national guidelines.7 Most of the podiatric surgery community is in agreement with the routine use of antibiotic prophylaxis in implantation of foreign materials and prostheses.7,15,17,21
Surgical site infections can drastically reduce quality of life and can impose an undue financial burden on the healthcare system. Current recommendations on the use of prophylactic antibiotics in elective surgery are based primarily on orthopedic studies that focus more on the hip and knee joints as well as the lower spine. There is a lack of strong, concise literature directly comparing infection rates for foot and ankle procedures with and without antibiotic prophylaxis. The limited studies relating to foot and ankle surgery currently available in the literature are not high-level studies as protocol, participants and methods are ambiguous.
Future directions for research include the influence of prophylaxis in foot and ankle surgery that involves implantation of hardware or internal fixation, various routes of pre-, intra- and postoperative antibiotic administration, and the effects of tourniquet application to improve patient care outcomes.
Mr. Patel is a second-year student at the Dr. William M. Scholl College of Podiatric Medicine at Rosalind Franklin University of Medicine and Science, and is a CLEAR-funded Summer Research Scholar. He is a Delegate to the American Podiatric Medical Students’ Association, President of the Rosalind Franklin University of Medicine and Science South Asian Medical Association, and a Student Ambassador for the Dr. William M. Scholl College of Podiatric Medicine.
Dr. Wu is the Dean and Professor of Surgery at the Dr. William M. Scholl College of Podiatric Medicine, and Professor of Stem Cell and Regenerative Medicine at the School of Graduate Medical Sciences at the Rosalind Franklin University of Medicine and Science in Chicago. She is also the Director of the Center for Lower Extremity Ambulatory Research (CLEAR) in Chicago.
1. Centers for Disease Control and Prevention. Surgical site infection (SSI) event. Available at: https://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf. Published January 2019. Accessed September 5, 2019.
2. Berríos-Torres SL, Umscheid CA, Bratzler DW, et al. Centers for Disease Control and Prevention guideline for the prevention of surgical site infection, 2017. JAMA Surg. 2017;152(8):784-791.
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