52 | wetenschapsdag 2023 Sessie 1d: Een Goede Fundering Voor de Chirurgische Lering 5 Auteurs R. Eelsing*, D. Penning*, M. van der Meer-Vos, C.J. Hodiamont, R.A.A. Mathot, T. Schepers Abstract titel Plasma and tissue concentrations after admission of 2g prophylactic cefazolin prior to lower extremity surgery – a substudy of the WIFI-2 randomized controlled trial Background To reduce the risk of infection, antibiotic prophylaxis is widely used and therefore part of the protocolled care for surgery using implants. In the Netherlands, the recommended dose of cefazolin is 2 grams for prophylaxis. However, the literature regarding recommendation of dosage is limited. The primary aim of this study is to measure cefazolin concentrations at different locations below the level of the knee in both venous plasma, target-site plasma and target-site tissue. Methods Between May 2021 and March 2023 we collected 143 samples of 27 patients during implant removal surgery. The venous plasma samples were collected at the upper extremities by means of a standard blood sample. Target-site plasma samples were collected by collecting blood samples out of the surgical wound with a syringe and target-site tissue was collected by a subcutaneous tissue biopsy of the surgical wound. The primary outcomes were the cefazolin concentrations in venous plasma, target-site plasma and target-site subcutaneous tissue. Secondary outcomes were the influences of several predictor variables on the cefazolin concentration. Cefazolin plasma and tissue concentrations were determined by using LC-MS/MS with electrospray ionization in the positive ionization mode on a Shimadzu LC-30 system coupled to a ABSciex 5500 Qtrap MS. Results The mean venous plasma, target-site plasma and target-site tissue concentrations of unbound cefazolin were 36 (±13) ug/mL, 29 (±13) ug/mL and 28 (±13) ug/g, respectively. Concentrations stayed well above the MIC(90) of the staphylococcus aureus for at least 80 minutes. And, except for a positive influence of an alcohol consumption of ≥2 units a day on the tissue concentration of cefazolin (p=0.029), no other predictors were found. Conclusion In conclusion, 2g of prophylactic cefazolin demonstrates adequacy in maintaining coverage for a duration exceeding 80 minutes of surgery below the level of the knee, significantly surpassing the MIC(90) required to combat the most pivotal microorganisms.
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