Infection Rates Based on Antibiotic Choice at the Time of Hysterectomy

Objectives: The objective of this study was to utilize a national database cohort to determine the role of antibiotic choice on surgical site infection (SSI) associated with hysterectomy. The primary outcome was SSI within 3 months of the index procedure. Secondary outcomes included SSI within 12 months, readmission, and emergency department visits.

Methods: This is a retrospective cohort study utilizing the Premier Healthcare Database. Patients were identified as having undergone hysterectomy between January 2000 and March 2020 using CPT codes. The patients were grouped by antibiotic regimen: cefazolin, cefazolin with metronidazole and any other regimen. Patient characteristics, surgical information and postoperative complications within 3 months and 1 year were collected. Data were analyzed using student t-test, chi square test, ANOVA, and multivariable logistic regression, as appropriate. Inverse probability of treatment weighting analysis was used to balance the groups on preoperative characteristics.

Results: The sample included 242,349 patients (Table 1). The most utilized prophylaxis was cefazolin alone, while 3.9% of patients received cefazolin with metronidazole. There were significantly more episodes of SSI, cellulitis, or abscess in those receiving “other” antibiotics when compared to those receiving either cefazolin or cefazolin with metronidazole (p < 0.001). Multivariate logistic regression revealed a significant relationship between SSI and tobacco use, obesity, Charlson Comorbidity Index, and diabetes (Table 2). The use of “other” antibiotic regimens was associated with an increased probability of developing a SSI, when compared with cefazolin alone (p=0.011). The addition of metronidazole to cefazolin did not significantly decrease the odds of developing a SSI (p>0.9). The estimated difference in risk of SSI at 3 months between the weighted cefazolin with metronidazole and cefazolin alone groups was 0.000 (95% CI: [-0.004, 0.004]) leading to a weighted odds ratio of 0.984 (95% CI: [0.810, 1.195]).

Conclusions: When matched on preoperative characteristics, the addition of metronidazole to cefazolin for prophylaxis at the time of hysterectomy did not significantly decrease the probability of developing a SSI compared to cefazolin alone. Any regimen of antibiotics other than cefazolin or cefazolin with metronidazole was associated with increased probability of SSI. Factors including obesity, tobacco use, Charlson Comorbidity Index, and diabetes were associated with increased SSI rates.