Study reports reduced SSI odds after gynecologic surgery from metronidazole and cefazolin

Study reports reduced SSI odds after gynecologic surgery from metronidazole and cefazolin | Image Credit: © RFBSIP - © RFBSIP - stock.adobe.com.

The risk of surgical site infection (SSI) from gynecologic surgery is significantly reduced by the addition of metronidazole to cefazolin beforehand, according to a recent study published in the American Journal of Obstetrics & Gynecology.¹

As one of the most common complications of gynecologic cancer surgery, SSI leads to increased health care costs and significant rates of postoperative morbidity. Cefazolin administration is recommended before the surgery to reduce the risk of SSI, but SSI rates remain significant among patients undergoing gynecologic procedures.²

Initiatives have been conducted to reduce SSI rates, with many focusing on preoperative interventions.¹ Data has indicated potential benefits from greater anaerobic coverage, but additional research is necessary.

To determine the efficacy of adding metronidazole to cefazolin before gynecologic surgery in reducing SSI rates, investigators conducted a retrospective cohort study. Participants included patients receiving a surgical procedure between May 18, 2017, and June 30, 2023, at MD Anderson Cancer Center’s department of gynecologic surgery and reproductive medicine.

Exclusion criteria included penicillin allergy, bowel procedures, joint procedures with multiple surgical teams, and not receiving preoperative antibiotics. Participants receiving the procedure from May 18, 2017, to April 19, 2022, were in the preintervention group, while those from April 20, 2022, to June 30, 2023, were in the postintervention group.

The intervention implemented on April 20, 2022, included cefazolin 2 g or 3 g, as well as metronidazole 500 mg before gynecologic oncology surgeries. Metronidazole was added to all cases where patients would have received cefazolin alone, except for those with a contraindication to metronidazole.

Re-doses of cefazolin were administered every 4 hours, while re-doses of metronidazole were administered every 12 hours. Additionally, patients received an additional dose if they experienced excessive blood loss over 1500 mL.

The 30-day SSI rate was reported as the primary outcome of the analysis. Secondary outcomes included wound-related complications. Data obtained through chart review included demographic, clinical, surgical, and SSI data.

There were 3343 patients included in the final analysis, 76.9% of whom were in the preintervention group and 23.1% were in the postintervention group. Of patients, 69.3% were White, 79.4% were non-Hispanic, 65.7% had a minimally invasive procedure, and 74.7% had hysterectomy as part of their surgery.

Of hysterectomies, 60% were minimally invasive while 40% were open. The odds of being a current smoker were 6.2% in the preintervention group vs 4% in the postintervention group, while rates of laparotomy were 35.8% vs 29.1%, respectively, and rates of appropriate preoperative antibiotics were 95.6% vs 90.7%, respectively.

Overall, the preintervention group had an SSI rate of 4.7%, vs 2.6% in the postintervention group. Preintervention SSI rates for open hysterectomy, minimally invasive hysterectomy, and benign indications were 7.8%, 3.4%, and 4.4%, respectively, vs 4.8%, 1.9%, and 2.4%, respectively, for postintervention SSI rates.

The overall odds ratio (OR) for SSI in the postintervention group vs the preintervention group was 0.49. Current smoking, increased body mass index, and higher hemoglobin A1C value were linked to increased SSI risk, with ORs of 2.15, 1.03, and 1.27, respectively. Of SSIs, 55.8% in the preintervention group and 65% in the postintervention group were superficial.

These results indicated a significant decrease in the overall SSI rate following gynecological surgery when adding metronidazole to cefazolin for prophylaxis before the procedure. Investigators concluded these results may be applicable to the broader field of gynecologic surgery, especially for hysterectomy procedures.

References

1. Knisely A, Iniesta MD, Marten CA, Chisholm G, Schmeler KM, Taylor JS. Metronidazole and cefazolin vs cefazolin alone for surgical site infection prophylaxis in gynecologic surgery at a comprehensive cancer center. American Journal of Obstetrics & Gynecology. 2024;231(3):326.E1-326.E13. doi:10.1016/j.ajog.2024.03.043
2. Mahdi H, Gojayev A, Buechel M, et al. Surgical site infection in women undergoing surgery for gynecologic cancer. Int J Gynecol Cancer. 2014;24(4):779-786. doi:10.1097/IGC.0000000000000126