Cefazolin tissue concentrations with a prophylactic dose administered before sleeve gastrectomy in obese patients: a single centre study in 116 patients

Background: In obese patients undergoing sleeve gastrectomy, the blood and fatty-tissue concentrations of cefazolin required for adequate antibiotic prophylaxis are uncertain. Methods: This was a single centre prospective study in obese (Group A: 40 <= BMI <= 50 kg m(-2)) and severely obese (Group B: 50 < BMI <= 65 kg m(-2)) patients undergoing bariatric surgery. Blood and fatty-tissue samples were collected after a cefazolin 4 g i.v. injection. The primary aim was to compare cefazolin concentrations in subcutaneous fatty tissue with a targeted tissue concentration of 4 mu g g(-1) according to Staphylococcus aureus resistance breakpoint. Results: One hundred and sixteen patients were included: 79 in Group A and 37 in Group B. At the beginning of the surgery, cefazolin concentrationin subcutaneous fatty tissue was 12.2 (5.4) mu g g(-1) in Group A and 12 (6.1) mu g g(-1) in Group B (P=0.7). At the end, cefazolin concentrations in subcutaneous fatty tissue were 9.0 (4.9) and 7.8 (4.2) mu g g(-1) in Groups A and B, respectively (P=0.2). The plasma concentration of free cefazolin during surgery was higher in Group A than in Group B (P<0.0001). Fatty tissue concentrations of 95% and 83% patients in Groups A and B, respectively, were above S. aureus resistance breakpoint. Conclusions: After a 4 g dose, the concentrations of cefazolin in fatty tissue were above the 4 mu g g(-1) tissue concentration target, providing adequate antibiotic tissue concentrations during bariatric surgery. As cefazolin concentration in fatty tissue is a surrogate endpoint, the results should be considered in conjunction with the results on free cefazolin concentrations in subcutaneous tissue.