Raised BMI is an independent risk factor for groin surgical site infections in patients undergoing varicose vein surgery To the Editor: Hirsemann et al 1 reported on the incidence of surgical site infection following outpatient surgery for hernias and varicose veins. In their study, the authors showed that the only independent risk factor was spinal anesthe- sia. We investigated the incidence of surgical site infec- tion in the groin following varicose vein surgery under general anesthetic and showed that body mass index (BMI) greater than 30 is an independent risk factor for the development of surgical site infection (SSI). A consecutive cohort of 210 cases was recruited to in- vestigate surgical site infection following all varicose vein operations involving groin incisions performed un- der general anesthetic at Wycombe General Hospital. The exposure variables studied were age, gender, Amer- ican Society of Anesthesiologists (ASA) score, and BMI. A standardized proforma was used for data collection at time of surgery and at assessment by a vascular special- ist nurse between 10 to 14 days postoperatively. Out- come was measured by the incidence of surgical site infection as diagnosed by the presence of criteria pub- lished by the Centers for Disease Control and Prevention (CDC). 2 A 2-tailed Fisher exact statistical test was per- formed to determine which risk factors significantly increased the risk of groin surgical site infection. The median age of patients was 53 years; 133 cases were female (63%), and 77 were male (37%); 131 pa- tients had an ASA score of 1 (62%), 68 patients an ASA score of 2, and 4 patients an ASA score of 3; 53 pa- tients had a BMI of greater than or equal to 30. There were 10 surgical site infections (4.8%) of the groin de- tected in the study (see Table 1). This prospective study shows that the incidence of surgical site infection after varicose vein surgery is 4.8%. Patients with BMI of 30 or above were 24 times more likely to develop surgical site infection in the groin incision than patients with a lower BMI. Elevated BMI is an independent risk factor for surgical site infection in varicose vein surgery, and patients with this risk factor should be warned accordingly. Increased BMI is likely to increase the risk of SSI because overhanging adipose tissue creates a moist environment in the groin, encour- aging the growth of opportunistic pathogens. The implications of these results are 2-fold. First, pro- phylactic antibiotics should be considered in patients with raised BMI undergoing varicose vein surgery. Al- though the role of prophylactic antibiotics is not clear in clean nonimplant wounds, 3 their use may be benefi- cial in this subgroup of patients. Further studies compar- ing these high-risk patients with and without antibiotics would be helpful in assessing the benefits of prophy- laxis and drawing up guidelines in antibiotic therapy. Second, novel treatments for varicose vein surgery that avoid groin incisions, such as radiofrequency abla- tion, laser therapy, and sclerotherapy could be offered to patients with increased BMI. 4,5 Because these proce- dures could be performed under local anesthesia in selected cases, this would have an added benefit in ob- viating the need for general anesthetic in obese pa- tients. Future studies comparing novel treatments with traditional groin surgery in relation to surgical site infection rates should be undertaken. We conclude that BMI is an independent predictor of surgical site infection in the groin after varicose vein surgery. Patients with BMI of 30 or greater should be considered for prophylactic antibiotics or surgery that avoids a groin incision. The authors thank G. Howat and S. Mosby for their help in data collection, as well as L. Yu for her assistance with statistical analysis. TrevorM. Yeung, MA, MBBChir, MRCS a Alexandra C. Cope, MBBS, MRCS a Niamh Whittome, RGN b Patrick Lintott, MD, FRCS a From the Department of General Surgery a and Department of Microbiology, b Wycombe General Hospital, High Wycombe, United Kingdom. E-mail: trevoryeung@doctors.org.uk References 1. Hirsemann S, Sohr D, Gastmeier K, Gastmeier P. Risk factors for sur- gical site infections in a free-standing outpatient setting. Am J Infect Control 2005;33:6-10. Table 1. Results of the univariate risk factor analysis No Yes Character- istics N No. with SSI % N No. with SSI % Odds Ratio P value Age . median (35 y) 102 4 3.92 106 6 5.67 1.44 .75 Male 133 5 3.76 77 5 6.49 1.72 .50 ASA .1 131 4 3.05 72 6 8.33 2.73 .07 BMI $30 142 1 0.70 53 9 17.0 24.11 <.001 * P values were calculated using 2-tailed Fisher exact test. * Significant. 0196-6553/$34.00 Copyright ª 2008 by the Association for Professionals in Infec- tion Control and Epidemiology, Inc. 152