1469. Pharmacodynamics of Antimicrobial Prophylaxis in Cardiac Surgery: Association between Intraoperative Cefazolin Concentrations and Postoperative Infections
Session: Poster Abstract Session: HAI: Surgical Site Infections
Friday, October 28, 2016
Room: Poster Hall
  • _2016 IDWeek AP PD Cardiac SSI Poster FINALsaz.pdf (526.7 kB)
  • Background: Although the benefits of antimicrobial prophylaxis (AP) are well established, studies that characterize antimicrobial activity in preventing surgical site infections (SSIs) are limited. The goal of this study was to conduct a pharmacodynamic analysis of intraoperative cefazolin concentrations and postoperative infections in patients undergoing cardiac surgery.

    Methods: A PD analysis was conducted using data from a prospective pharmacokinetic study of cefazolin during cardiac surgery with cardiopulmonary bypass. Cefazolin prophylaxis was administered as per standard practice. Blood samples were collected after the preoperative dose, prior to intraoperative doses and within 15 minutes of wound closure. Cefazolin plasma concentrations were measured using liquid chromatography with tandem mass spectrometric detection. Patient and surgery data were collected from medical records, and SSIs were monitored for 30 days after surgery. Univariate analysis was used to identify potential risk factors for SSI (eg, age, body weight, cefazolin prophylaxis, duration of surgery) and multivariate analysis was performed with significant variables (p<0.1) using a backward, stepwise approach in a binary logistic-regression model (SYSTAT®).

    Results: Forty patients (65 ± 10 years, 88 ± 16 kg) with complete data were included in the analysis. A mean preoperative cefazolin dose of 23.5 ± 5.4 mg/kg was administered 35 ± 13 minutes prior to incision. At least one additional intraoperative dose was given in 30 cases. The mean duration of surgery was 243 ± 71 minutes, and median [IQR] cefazolin closure concentration (concclos) was 88.5 [50.4 – 139.5] mg/L. Eight patients received antimicrobial therapy for a superficial SSI. In the final logistic-regression model, surgery duration (p=0.02) and cefazolin concclos (p=0.04) were the only independent variables associated with SSI. Critical thresholds identified using Classification and Regression Tree (CART) analysis were surgery duration <346 minutes (SSI rate of 14.3% versus 60%) and cefazolin concclos >104 mg/L (SSI rate of 5.9% versus 30.4%).

    Conclusion: This study demonstrates the potential importance of cefazolin concentration at wound closure (concclos) in providing optimal AP and preventing postoperative infections in patients undergoing cardiac surgery.

    Sheryl Zelenitsky, PharmD1,2, Divna Calic, BSc(Pharm)1, Robert Ariano, PharmD1,2, Rakesh Arora, MD1,2 and Hilary Grocott, MD1,2, (1)University of Manitoba, Winnipeg, MB, Canada, (2)St. Boniface Hospital, Winnipeg, MB, Canada


    S. Zelenitsky, None

    D. Calic, None

    R. Ariano, None

    R. Arora, None

    H. Grocott, None

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