This study investigates whether current cefazolin dosing guidelines for obese patients-2 g IV for those \<120 kg and 3 g IV for those ≥120 kg-achieve adequate plasma and tissue concentrations (≥8 mg/L) for effective surgical prophylaxis. While several retrospective and prospective studies suggest that a 2 g dose may be sufficient regardless of weight, findings are inconsistent and often rely solely on plasma concentrations. Given that tissue concentration at the site of action is a more relevant pharmacokinetic marker, the study emphasizes the need to measure cefazolin levels in adipose tissue. Previous research using microdialysis has shown reduced tissue distribution in obese patients, potentially warranting higher doses. The study also highlights variability in defining the minimum inhibitory concentration (MIC) required for prophylaxis, noting that 8 mg/L is often considered the threshold for Enterobacteriaceae. Ultimately, the study aims to clarify whether current dosing achieves effective antibiotic levels across different weight categories, with a focus on tissue concentrations.
Study Type
OBSERVATIONAL
Enrollment
70
Institut universitaire de cardiologie et de pneumologie de Québec - Université Laval
Québec, Quebec, Canada
Area Under the Concentration-Time Curve (AUC) of Cefazolin in Plasma, Adipose Tissue, and Dermal Tissue
AUC of cefazolin will be measured in plasma, adipose tissue, and dermal tissue at 0 minutes, 30 minutes, and at the end of surgery following administration according to current dosing guidelines. Unit of Measure: mg·min/L
Time frame: During surgery
Proportion of Patients Achieving Cefazolin Tissue Concentrations ≥ 8 mg/L
Proportion of patients with adipose and dermal tissue concentrations of cefazolin ≥ 8 mg/L at any time point (0 min, 30 min, end of surgery), based on the MIC for Enterobacteriaceae. Unit of Measure: Percentage of patients (%)
Time frame: During surgery
Proportion of Patients Achieving Cefazolin Plasma Concentrations ≥ 2 mg/L
Proportion of patients with plasma concentrations of cefazolin ≥ 2 mg/L at each time point (0 min, 30 min, end of surgery), based on the MIC for methicillin-sensitive Staphylococcus aureus (MSSA). Unit of Measure: Percentage of patients (%)
Time frame: During surgery
Comparison of Cefazolin Concentrations Across Weight Categories
Comparison of plasma and tissue concentrations of cefazolin across weight categories (\<120 kg, 120-149 kg, ≥150 kg) to identify potential underexposure in higher weight groups. Unit of Measure: Mean concentration (mg/L)
Time frame: During surgery
Tissue-to-Plasma Concentration Ratio of Cefazolin
Ratio of cefazolin concentration in tissue to plasma at each time point to assess distribution efficiency. Unit of Measure: Ratio (unitless)
Time frame: During surgery
Time Above MIC (T>MIC) for Cefazolin in Plasma and Tissue
Duration (in minutes) that cefazolin concentrations remain above MIC in plasma and tissue compartments, if additional time points are available. Unit of Measure: Minutes
Time frame: During surgery
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