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ORIGINAL RESEARCH |
From the Divisions of Special Gynaecology and Obstetrics and Gynaecology, Department of Obstetrics and Gynaecology, University of Vienna, Vienna, Austria.
Address reprint requests to: Armin Witt, MD, University School of Medicine, Vienna, Department of Obstetrics and Gynaecology, Währinger Gürtel 18–20, A-1090 Vienna, Austria; E-mail: armin.witt{at}akh-wien.ac.at.
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ABSTRACT |
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METHODS: In a prospective evaluation of 326 patients undergoing breast surgery, we identified risk factors for wound infections by univariate analysis and subsequent step-wise multiple logistic regression. Assessment of wound infection was based on a simple wound scoring system.
RESULTS: Of the 326 patients, 50 (15.3%) developed wound infections. As expected, after univariate analysis a higher proportion of postsurgical infections was observed in patients with diabetes (33.3% versus 14.3%; odds ratio [OR] = 3.00, 95% confidence interval [CI] 1.109, 8.157; P = .03) and malignant tumors (21.2% versus 6.8%; OR = 3.716, 95% CI 1.762, 7.849; P < .001). Patients with wound infections were significantly older than those without (mean age 63.73 versus 51.44 years, P < .001). Surprisingly, patients who underwent core needle biopsy, which in most cases was performed within 1–3 days before breast surgery, were also at significantly higher risk for developing a wound infection (22.3% versus 9.6%; OR = 2.718, 95% CI 1.454, 5.076; P = .001). This effect remained unchanged when controlled for potential confounders by step-wise multiple logistic regression.
CONCLUSION: In breast surgery, the independent risk factors for wound infections are older age and preoperative core needle biopsy.
The reported rate of postoperative wound infections in patients undergoing breast surgery lies between 3%1 and 19%.2 An important reason for these diverging findings may be that the definition of wound infection is not standardized. Thus, some definitions include simple criteria, such as the presence of pus alone,3 whereas others require the concurrent presence of several indicators, for example the classification of the United States Center for Disease Control and Prevention, which defines infection as a wound with purulent drainage, positive wound cultures, wound dehiscence, and physician notation of infection.3 Still others are based on highly complex wound scoring algorithms (Wilson AP, Webster A, Gruneberg RN, Treasure T, Sturridge MF. Repeatability of asepsis wound scoring method [letter]. Lancet 1986;1:1208–9).
Moreover, little is known regarding the possible risk factors for wound infection and their relative importance. Research has either yielded contradictory results or not taken into account all factors potentially playing a role in the development of wound infection.4,5 Yet the psychological trauma and cosmetic consequences associated with infectious complications after breast surgery underscore the need for pertinent clinical trials.
One purpose of this study, therefore, was to determine, as part of our internal quality control program, the wound infection rate in 326 women undergoing breast surgery, with the diagnosis of wound infection based on a newly developed scoring method. A further objective was to explore a number of factors that may have an impact on the rate of infection of surgical wounds, placing particular emphasis on the influence of preoperative procedures such as core needle biopsy, a technique commonly used at our department to establish a diagnosis of breast cancer. Our results suggest that, in addition to the "known" risk factors for postoperative wound infection, such as older age, diabetes mellitus, and malignancy, core needle biopsy is an independent risk factor for wound infection.
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MATERIALS AND METHODS |
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ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). In most cases, a chest wall drain and an axillary vacuum drain were inserted. Lumpectomies usually comprised wide local excision. Re-excision was performed when clinically indicated, but patients undergoing re-excision were excluded from the final analysis. The skin was closed in one layer. The axillary lymph nodes were dissected by separate incision, except when tumors were localized in the upper outer quadrant of the breast. Before closure, clean instruments and new gloves were used. All drains were removed when the drainage volume decreased to less than 25 mL in 24 hours. Patients started shoulder exercises on the day after the operation. Postoperative wound assessment was based on a simple wound scoring method, with the diagnosis of wound infection requiring the presence of at least one of the following criteria: 1) wound erythema greater than 1 cm, 2) purulent wound surface, 3) purulent wound dehiscence, or 4) more than 1 day of fever above 37.5C. Depending on the severity of infection, treatment was provided on an inpatient or outpatient basis. In patients whose postoperative course was uneventful, surgical wound status was again assessed at the routine follow-up examination using the wound scoring system described above. In addition to the parameters obtained preoperatively, we collected a number of treatment-related data, including date and type of operation, preoperative core needle biopsy, date of biopsy, biopsy lesion markers, length of time mammary and axillary drains were left in place, time to discharge, smear, and puncture. Moreover, the presence or absence of wound infection at discharge and at follow-up was recorded. We did not evaluate risk factors such as obesity, body mass index, drainage volume, impact of surgeon skills, and duration of surgery.
The impact of the recorded data on wound infection rates was analysed. Cross-tabulation of the data with presence or absence of wound infection and subsequent 
2 or, where appropriate, Fisher exact tests for categorical data and t tests for continuous variables were first used to assess possible risk factors for infection. Odds ratio (OR) estimates were obtained by using Cornfield approximation (Woolf if Cornfield was not calculable), and 95% confidence intervals (CIs) were computed. Step-wise multiple logistic regression analysis was used to develop and test a model for risk factors. The criterion for elimination of parameters was set to P = .15. All statistical tests were two-tailed.
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RESULTS |
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. Of the 326 patients, 50 (15.3%) recruited into the study developed wound infections, with 33 (10.1%) cases first diagnosed during primary hospitalization and 17 (5.2%) at the time of the follow-up visit. Of interest, the wound infections detected after discharge tended to be more severe than those diagnosed in-hospital (Figure 2). The mean hospital stay for patients with postoperative wound infection was significantly longer than for patients without infection (7.84 versus 4.71 days, P < .001) (Table 2).
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. As expected, a higher proportion of postsurgical infections was observed in patients with diabetes (33.3% versus 14.3%; OR = 3.000, 95% CI 1.109, 8.157; P = .03) and malignant tumors (21.2% versus 6.8%; OR = 3.716, 95% CI 1.762, 7.849; P < .001). Likewise, the surgical procedure was found to have an influence on wound infection rates, with 33.3% of patients undergoing mastectomy, 42.4% of patients undergoing mastectomy with axillary dissection, 6.9% of women undergoing lumpectomy, and 23.5% of women undergoing lumpectomy with axillary dissection developing postsurgical wound infections (P < .001). Patients with wound infections were significantly older than those without (mean age 63.73 versus 51.44 years, P < .001). In contrast, preoperative marking (10.6% versus 19.3%, P = .190) did not appear to have an influence on the rate of wound infections, regardless of the operative technique used. Likewise, neoadjuvant chemotherapy was not found to have influenced the patients’ susceptibility to wound infections.
Surprisingly, patients who underwent core needle biopsy, which in most cases was performed within 1–3 days before breast surgery, were also at significantly higher risk for developing a wound infection (22.3% versus 9.6%; OR = 2.718, 95% CI 1.454, 5.076; P = .001). This effect remained unchanged when controlled for potential confounders, such as age, benign versus malignant disease, diabetes, and preoperative marking using step-wise multiple logistic regression (Table 3).
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DISCUSSION |
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With regard to the known risk factors for postoperative wound infection, our results outside the regression model are comparable to those of previous studies. The age dependency of wound infections (OR = 1.70, 95% CI 1.49, 1.94; per 10 years) in our study is similar to previous findings.6–8 A significantly higher wound infection risk (33.3%; OR = 3.00, 95% CI 1.11, 8.16) was observed in patients with diabetes mellitus, correlating well with data in the literature. A higher risk for wound infection (21.2%; OR = 2.19, 95% CI 1.45, 3.30) was also observed in patients with malignant tumors. The wound infection rates seen with different operative techniques are mostly related to the tumor diagnosis (benign or malignant). However, of the known risk factors for postoperative wound infection investigated in our study, patient age after adjustment was the only independent factor associated with postoperative wound infection.
Additionally, our findings support the conclusion that preoperative core needle biopsy, a factor that so far has not been considered in reviews of wound infection risk, is an independent risk factor for postoperative wound infection. One explanation for the relationship between core needle biopsy and postoperative wound infection may be that the possibility for the late sequelae of biopsy and the requirement for adequate hygienic practices are often underestimated. This may result in dissemination of skin germs into the puncture site, with the subsequent surgical intervention in turn enhancing the propensity for infection. Based on our results, we believe that prophylactic coverage with antibiotics is indicated to prevent postoperative wound infections in breast surgery, even though additional research will have to determine the optimal time of application–at the time of biopsy, during breast surgery, or on both occasions. Another strategy to reduce the risk of wound infection may be to increase the interval between core needle biopsy and definitive surgery. However, because most of our patients underwent surgery within 24 hours of biopsy, we were unable to find a significantly reduced infection rate in those patients with a longer wait following the biopsy.
Moreover, our findings emphasize the need for close medical supervision and careful clinical follow-up. Thus, 5% of our patients were first diagnosed as infected at the time of the follow-up examination, with these infections being significantly more severe than those detected during primary hospitalization, a finding that reconfirms the data reported by Platt et al.9 Lack of careful medical follow-up may lead to delays in diagnosis and treatment of postsurgical infection, resulting in a sharp increase in cost, prolonged hospitalization, and more frequent follow-up visits.
In view of the psychological trauma and cosmetic consequences associated with infection after breast surgery, the above described risk factors, and particularly combinations thereof, should be considered important determinants in decisions regarding the use of perioperative antibiotic prophylaxis.
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Footnotes |
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Received March 26, 2002. Received in revised form August 23, 2002. Accepted September 5, 2002.
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REFERENCES |
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2. Rotstein C, Ferguson R, Cummings KM, Piedmonte MR, Lucey J, Banish A. Determinants of clean surgical wound infections for breast procedures at an oncology center. Infect Control Hosp Epidemiol 1992;13:207–14.[Medline]
3. Garner JS, Jarvis WR, Emori TG, Horan TC, Hughes JM. CDC definitions for nosocomial infections, 1988. Am J Infect Control 1988;16:128–40.[Medline]
4. Lipshy KA, Neifeld JP, Boyle RM, Frable WJ, Ronan S, Lotfi P, et al. Complications of mastectomy and their relationship to biopsy technique [see comments]. Ann Surg Oncol 1996;3:290–4.[Abstract]
5. Rappaport W, Thompson S, Wong R, Leong S, Villar H. Complications associated with needle localization biopsy of the breast. Surg Gynecol Obstet 1991;172:303–6.[Medline]
6. de Boer AS, Mintjesde Groot AJ, Severijnen AJ, van den Berg JM, van Pelt W. Risk assessment for surgicalsite infections in orthopedic patients. Infect Control Hosp Epidemiol 1999;20:402–7.[Medline]
7. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Engl J Med 1996;334:1209–15.
8. Vinton AL, Traverso LW, Jolly PC. Wound complications after modified radical mastectomy compared with tylectomy with axillary lymph node dissection. Am J Surg 1991; 161:584–8.[Medline]
9. Platt R, Zaleznik DF, Hopkins CC, Dellinger EP, Karchmer AW, Bryan CS, et al. Perioperative antibiotic prophylaxis for herniorrhaphy and breast surgery. N Engl J Med 1990; 322:153–60.[Abstract]
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