End-of-procedure cefazolin concentrations after administration for prevention of surgical-site infection

The adequacy of end-of-procedure free cefazolin concentrations after administration for the prevention of surgical-site infection (SSI) and compliance with national guidelines for antimicrobial prophylaxis for SSI were assessed. Patients undergoing elective surgery and receiving cefazolin for perioperative antimicrobial prophylaxis were prospectively enrolled. Antibiotic administration was controlled by the surgeon and usage was recorded. For each patient, a single blood sample for cefazolin serum free and total concentrations was obtained within 15 minutes of wound closure. A free serum concentration threshold of 4 microg/mL was arbitrarily chosen based on the minimum inhibitory concentration required to inhibit 90% of strains of methicillin-susceptible Staphylococcus aureus and Escherichia coli. Fifty-seven subjects were enrolled, and noncompliance with published guidelines was observed for 26% of patients. Forty-six subjects had serum samples available for assay, 21.7% of whom had end-of-procedure free cefazolin concentrations of