Summary: Assessing the Need for Infection Prophylaxis

•The incidence of transient bacteremia with dermatologic surgery on noninfected skin appears to be no greater than the incidence with routine daily activities.

•Updated guidelines from the American Heart Association and the American College of Cardiology in 2007 limit prophylactic antibiotics only to those patients with cardiac conditions at highest risk for endocarditis undergoing surgery with breach of the oral mucosa or on infected cutaneous sites.

•Prophylactic antibiotics should also be considered in patients with recent total joint replacement, or in surgical sites at high risk for postoperative wound infection.

•There is no evidence to support the use of prophylactic topical antibiotic preparations in dermatologic surgery.

Table 3.2 Cardiac conditions at high risk for infective endocarditis

Prior history of infective endocarditis

Prosthetic cardiac valve or prosthetic valvular material

Cardiac transplantation recipients who develop cardiac valvulopathy

Congenital heart disease (CHD)

Unrepaired cyanotic CHD including palliative shunts and conduits

Completely repaired CHD with prosthetic material or device during first 6 months after procedure

Repaired CHD with residual defects at site or adjacent to site of prosthesis

Data obtained from Wilson et al. [36]

rather than true infection. These studies suggest that the risk of bacterial bloodstream infections after surgery on eroded, noninfected skin is exceedingly low, and that the risk of bacteremia is not higher in Mohs surgery compared to standard excisional surgery. Although there have been published reports of bacterial endocarditis occurring after surgical procedures on noninfected skin [35], it is not clear that these procedures represent a greater risk of endocarditis than the baseline risk of normal activities.

In light of these findings and the increasing recogni-

Prophylaxis

Dermatologic surgery is remarkably safe, but the surgical disruption of the epidermal barrier creates an inevitable risk of infection. Of particular concern is the potential for bacterial endocarditis and prosthetic joint infection in predisposed individuals. Both of these lifethreatening infections involve seeding of susceptible anatomic sites (either exogenous hardware or previously damaged valves) in the setting of bacteremia. At least transient bacteremia is thought to be a prerequisite to bacterial endocarditis or septic arthritis. Reliable data suggests that the rate of bacteremia immediately following cutaneous surgery is negligible: 2.7% of 149 patients had positive blood cultures after surgery, compared with 3.3% of these patients prior to surgery and 2.1% of 240 healthy control patients without skin lesions [33, 34]. The surgeries performed in this study included basic excisional and Mohs surgery with linear, flap, and graft repair, and 31% of the skin lesions were eroded at the time of surgery. In addition, the bacteria isolated in all cases were nonpathogenic skin flora and were thought to represent contamination

use, including allergic reactions, antibiotic-associated colitis, and bacterial resistance, updated guidelines from the American Heart Association (AHA) in 2007 now recommend prophylactic antibiotics only in certain patient populations under specified conditions [36]. The guidelines acknowledge that there is insufficient data to support the use of routine antibiotic prophylaxis in most surgical patients, that antibiotic prophylaxis may only prevent an exceedingly small number of cases of infective endocarditis, if any, and that the potential adverse effects associated with antibiotic use outweigh the benefit of prophylaxis for most patients. These guidelines were summarized in the dermatology literature with particular attention to dermatologic procedures in 2008 [37], and are presented in Table 3.2 and Fig. 3.4.

The first step in the algorithm (Fig. 3.4) is determining whether a patient has an underlying cardiac condition conferring significantly increased risk and exacerbated complications of infective endocarditis. These conditions are limited to prior infective endocarditis, prosthetic heart valves, valvulopathy following cardiac transplantation, and congenital heart disease as described

in Table 3.2. Other cardiac conditions such as mitral valve prolapse, mitral or aortic regurgitation, indwelling pacemakers, and intracoronary stents are not indications for antibiotic prophylaxis. The next consideration in the decision to prescribe antibiotic prophylaxis is the surgical site. Because of the increased microbial burden on mucosal sites and the difficulty in sterilizing the oral cavity preoperatively, procedures that disrupt the epithelial barrier of the oral mucosa incur a greater risk of bacteremia and subsequent endocarditis. As such, prophylaxis is recommended for surgery that penetrates the oral mucosa in patients with high-risk cardiac conditions. Surgical procedures involving the nasal mucosa are not specifically addressed in the AHA guidelines, and the decision to provide antibiotic prophylaxis for these cases must therefore be considered on a case-by- case basis. The next step is the assessment of clinical signs of infection at the operative site. The current AHA guidelines draw a distinction between surgical procedures on normal skin and infected skin, citing the evidence that procedures on normal skin have an essentially negligible risk of bacteremia, even in the presence of superficial erosions. If there is clinical evidence of local skin infection such as erythema, edema, and purulent discharge, the lesion should be cultured and the patient treated with a full course of systemic antibiotics, with delay of surgery to coincide with completion of the antibiotic regimen. In this case, antibiotic treatment is both therapeutic for local infection and prophylactic for prevention of endocarditis.

The final step in the algorithm is to determine whether the surgical site is at significantly increased

risk of postoperative wound infection. The rationale for this comes from the fact that local skin infections (even in the absence of surgery) may lead to transient bacteremia, and skin infection has been associated with an increased risk of bacterial endocarditis [38]. As such, prophylactic antibiotic use to prevent postoperative wound infection is expected, but not proven, to decrease the risk of infective endocarditis. While the use of antibiotic prophylaxis for skin sites at increased risk of local infection is not specified in the AHA guidelines, this practice has been advocated in the dermatology literature [37]. Several studies have been performed to quantify the incidence of surgical site infections after dermatologic procedures. A prospective study of 5,091 Mohs and excisional surgical cases without antibiotics confirmed the overall low incidence (1.47%) of postoperative surgical site infections in dermatology and identified the following sites or repairs at greater than 5% risk of infection: any site on the lower leg below the knee (6.92%), sites in the groin (10%), wedge resection of the lip or ear (8.57%), and skin grafts at any site (8.7%) [39]. Sites on the fingers and flap repair at all sites had an intermediate risk of infection at 4.88% and 2.94%, respectively. A subsequent prospective study of 1,115 Mohs cases found an overall surgical site infection incidence of 0.7%, with only a modest increase in risk with flap repair (2.4%) and no evidence of infection in cases on the lip, ears, groin, or lower leg, although the number of cases in these sites was not reported [40]. In light of these studies, antibiotic prophylaxis may be considered in patients undergoing cutaneous surgery with elevated risk for local

Table 3.3 Selection of antibiotic dose and timing for infection prophylaxis

Reprinted from Wright et al. [37], Copyright 2008, with permission from Elsevier aAntibiotic to be administered as single dose, 60 min prior to procedure

infection such as cases on the lower leg and groin, wedge resection of lip or ear, or cases repaired with full-thickness skin grafts. Prophylaxis may also be considered for flap repairs and repairs on the fingers, although the data is less clear in this case. It must be emphasized, however, that without data to demonstrate a clear benefit of prophylaxis for patients with these higher risk sites, definitive recommendations cannot be made.

Once the decision has been made to provide prophylactic antibiotic therapy, the AHA guidelines are clear regarding the selection, dose, and timing of antibiotic administration. For surgical procedures involving oral mucosa, the most frequent cause of subsequent bacteremia is viridans group streptococci, and antibiotic therapy should therefore be targeted against this organism. Oral amoxicillin has been shown to be the most effective with minimal side effects; a single 2-g dose given 1 h prior to surgery is therefore recommended for oral procedures. For cutaneous procedures requiring prophylaxis, either due to clinically infected skin or surgery at high risk for local infection, the most frequent pathogens are Staphylococcus aureus and beta-hemolytic Streptococci. Standard prophylaxis is therefore a single dose of oral cephalexin, 2 g given 1 h prior to surgery. Patients with penicillin allergy should be treated with either clindamycin or a macrolide

antibiotic. Patients unable to take oral medication can be treated with either parenteral cephalosporins such as cefazolin or ceftriaxone, or parenteral clindamycin in the case of penicillin allergy. These recommendations, adapted from the AHA guidelines [36] and the dermatology literature, [37] are summarized in Table 3.3. It should also be noted that the most recent guidelines do not recommend an additional postoperative antibiotic dose for typical surgical procedures. For prolonged Mohs surgery lasting more than 4 h, a second dose at half strength (e.g., 1 g of cephalexin) can be given 6 h after the initial dose. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) of both community-acquired and healthcare-associated strains is increasing throughout the world, and postoperative local infections with MRSA have been reported after dermatologic surgery [40]. While the dermatologic surgeon must consider the possibility of MRSA and other resistant bacteria in all skin and subcutaneous surgical site infections, the lack of data regarding the true incidence of MRSA infection and the potential side effects of broad-spectrum antibiotics active against MRSA preclude the use of routine prophylaxis for this agent at this time.

Analogous to patients with prosthetic cardiac valve replacement, patients with prosthetic joint replacement exhibit an increased risk of seeding the joint

space from transient bacteremia and are more likely to have significant morbidity from joint space infection than patients with native joints. The American Dental Association and the American Academy of Orthopedic Surgeons have specified guidelines to specify which patients with prosthetic joint replacement will benefit most from antibiotic prophylaxis before surgical procedures [41]. The most critical period for prosthetic joint infection is the first 2 years postoperatively, and prophylaxis is therefore only required for procedures within 2 years of joint replacement for most patients. Other patient factors are thought to increase the risk or consequences of prosthetic joint infection such that prophylaxis is recommended for oral surgical procedures occurring beyond 2 years after joint replacement. These include history of previous prosthetic joint infection, immunocompromised patients with autoimmune disease or on immunosuppressive medication, patients with insu- lin-dependent diabetes, HIV infection, malignancy, malnutrition, or hemophilia. Patients with orthopedic pins, plates, or screws do not require routine prophylaxis. As in the algorithm for prevention of infective endocarditis (Fig. 3.2), prophylaxis for these patients should only be given if the planned procedure will breach oral mucosa, if the surgical site shows clinical signs of local infection, or if the procedure is at high risk for surgical site infection. The choice and timing of antibiotic prophylaxis is also analogous to the prevention of endocarditis and depends upon whether the surgical site is likely to introduce mucosal or cutaneous flora (Table 3.3).

In addition to preoperative prophylaxis for endocarditis and prosthetic joint infection, many dermatologic surgeons may prescribe antibiotics either preor postoperatively to decrease the risk of local surgical site infection. This is a controversial subject without clear data to support clinical practice decisions and is beyond the scope of this discussion. It should be noted, however, that postoperative antibiotics are expected to have limited preventive effect since bacteria become embedded within fibrin clots intraoperatively and may be relatively sequestered from circulating antibiotics [42]. Thus, if prophylaxis is desired, it should ideally be given as a single dose 1 h prior to surgery as outlined in Table 3.3. This prophylactic regimen is also likely to minimize adverse reactions such as antibi- otic-associated colitis and interaction with other medications, as well as decrease the emergence of bacterial

resistance and limit medical expenditures, as total use of antibiotics is reduced. Prophylaxis for surgical site infections should also take into account patient factors that may increase the risk of postoperative infection, such as immunocompromise, diabetes, or extensive inflammatory skin disease. These factors, coupled with the site-specific and procedure-specific risk of local infection as discussed above, can help select patients most likely to benefit from antibiotic prophylaxis.

In an attempt to provide infection prophylaxis without the potential side effects of systemic antibiotics, some surgeons may prescribe topical antibiotic ointments postoperatively. This practice is not supported by the literature. A prospective, blinded trial comparing bacitracin and petrolatum ointment for postprocedure skin wounds from skin biopsies, excisions, and Mohs surgery found that while bacitracin decreased the incidence of local infection with Staphylococcus aureus, there was a corresponding increase in infections with gram-negative bacteria. The total rate of wound infection was no different between the groups, and 4 of 444 patients in the bacitracin group developed allergic contact dermatitis to the antibiotic [43]. A more potent topical anti-Staphylococcal antibiotic, mupirocin ointment, was also evaluated in a trial of postoperative surgical wounds [44]. Mupirocin was similarly found to confer no benefit for prevention of surgical site infection, although there was a higher incidence of skin edge necrosis in the mupirocin group than paraffin ointment control (1.1% versus 0.1%). The significance of the latter finding is unknown, but due to the lack of evidence for efficacy of topical antibiotic preparations in local infection prevention, routine use of these agents for prophylaxis is not recommended.

Dermatologic procedures on the cutaneous or mucosal lip induce epidermal injury and can lead to reactivation of latent herpes virus infection. Questioning patients about cold sores or fever blisters is an important part of the preoperative evaluation. Any patient with a potential history of herpes labialis under going dermatologic surgery on the lip should receive prophylaxis with oral antiviral medications. Several regimens are available, including acyclovir 400 mg three times daily, valacyclovir 500 mg twice daily, and famciclovir 250 mg twice daily. Prophylaxis should be started on the day of surgery or 1 day prior and should be continued for an additional 3–5 days. Resurfacing