Scrutinizing incidence of surgical site infections

The indications for the administration of prophylactic antibiotics are many, with a long list of well-known risk factors in the development of surgical site infections (SSIs) hovering over the head of the Mohs surgeon prior to each procedure he or she performs.

Sherry L.H. Maragh, M.D., and Marc D. Brown, M.D., Mohs surgeons from Strong Memorial Hospital at the University of Rochester Medical Center, Rochester, N.Y., conducted a prospective study to evaluate the rate of SSIs among Mohs micrographic surgery (MMS) patients without the use of prophylactic antibiotics in order to assess the actual need for the administration of antibiotics prior to a Mohs procedure.

In the study, Dr. Maragh followed closely the surgical sites of 1,000 consecutive patients who underwent MMS for nonmelanoma skin cancer or modified MMS/"slow Mohs" for malignant melanoma in situ, excluding those patients who required prophylactic antibiotics for prevention of endocarditis or prosthetic infections.

Also excluded were patients who were referred to other surgeons for closure. In the 1,000 patients included in the study, 1,115 tumors were excised, 1,039 wounds were closed with primary intention and 76 wounds were closed with secondary intention or granulation. Of the 1,039 wound closures, 296 were done with flaps, 154 were done with skin grafts and 596 were closed via primary complex.

Significant study findings

Final results showed that out of the 1,000 patients with 1,115 tumors who underwent a Mohs procedure, there were only eight SSIs, or a rate of 0.7 percent.

The eight surgical sites broke down into five noses (all bilobed closures), one dorsal hand (primary closure), one chin (advancement) and one scalp (rotation). Dr. Maragh notes that 62.5 percent of the SSIs occurred on the nose, with an overall infection of nose cases being five out of 302 cases (~1.7 percent); 87.5 percent of the SSIs were flap closures, with an overall infection rate of flap closures being seven out of 296 cases (~2.4 percent); and 50 percent of the SSIs were multistaged cases, with an overall infection rate of multistaged procedures being four out of 487 cases (~0.8 percent).

Also of note, 25 percent of the SSIs had positive cultures for methicillin-resistant Staphylococcus aureus. This phenomenon is of interest because of the recent increased numbers of community-acquired cases.

All of the patients were evaluated two weeks after the one-week follow-up appointment. The investigators noted that there were no signs or symptoms of infection at the time of follow-up in any of the patients. The criteria for infection included any degree of erythema with edema, warmth, tenderness and/or purulent discharge. Wound cultures were obtained if an SSI was present, with antibiotic selection based on the results of the culture.

Potential prophylaxis parameters

Dr. Maragh outlines the eventual scenarios for the potential administration of prophylaxis for SSIs.

She says flap or graft reconstruction on the nose and ear, involvement of mucosal surfaces, high-tension closures, extended length of surgery, multiple simultaneous procedures, below-the-knee procedures and hand surgery all may be situations in which the Mohs surgeon may want to think twice and seriously consider the administration of antibiotics to the patient.

"The rates among patients undergoing dermatologic surgery including Mohs are exceedingly low. Therefore, it behooves the Mohs surgeon to be critical in his/her decision on prophylactic antibiotic therapy. Indiscriminate use of antibiotics increases the patient risk to adverse drug reactions and antibiotic resistance. I believe that the administration of antibiotics to Mohs patients should be on a case-by-case basis according to the clinical judgment of the surgeon," Dr. Maragh explains.