Single dose of cefazolin 2 grams prophylaxis in bariatric surgery patients: a pilot study

Purpose: Cefazolin is the first line antibiotic for prevention of surgical site infections (SSIs) in bariatric surgery. Staphylococcus aureus is a common cause of SSIs in the deep abdominal space. A minimal inhibitory concentration (MIC) of approximately 1mg/L for Staphylococcus aureus is considered to be acceptable. There are many controversies regarding cefazolin dosing in the morbidly obese population in the current medical literature. Some studies support the use of the 1 gram dose, while others support 2 grams or even higher. The goal of this study was to determine whether a single dose of cefazolin 2 grams IV push used prophylactically can provide an adequate MIC in the blood, subcutaneous adipose tissue, and the deep organ space during bariatric surgery. Methods: This study was a prospective observational pharmacokinetic study. The study recruited 37 patients undergoing Roux-enY Gastric Bypass (RYGB) or Laparoscopic Sleeve Gastrectomy (LSG), aged 18-60 years old, and with a body mass index (BMI) Z35kg/m. Patients who were pregnant, had moderate renal impairment (Serum creatinine41.5mg/dl), or were allergic to penicillin were excluded from this study. Patients received one dose of cefazolin 2 grams IV push within 15 minutes prior to the skin incision. The following samples were collected at the time of initial incision and before the skin closure: 2 grams of superficial fatty tissue, 2 grams of fatty-deep peri-gastric tissue and a serum sample. Cefazolin concentrations were determined by using the high-pressure liquid chromatography (HPLC) method. Results: At the current stage of the study, data from 19 patients was available. The mean cefazolin concentration at incision in the blood, subcutaneous adipose tissue, and peri-gastric adipose tissue were 134.18 þ 47.34 ug/mL, 10.47 þ 5.92 ug/mL, and 9.76 þ 6.23 ug/mL. At the completion of the procedure (last suture), the mean concentration of cefazolin in the blood, subcutaneous adipose tissue, and peri-gastric adipose tissue were 88.95 þ 32.11 ug/mL, 6.71 þ 4.81 ug/mL, and 6.76 þ 2.21 ug/ mL for sleeve only surgeries, 95.5 þ 11.88 ug/mL, 10.51 þ 0.83 ug/mL, and 20.51 þ19.22 ug/mL for sleeve with other procedures, and 71.08 þ 13.36 ug/mL, 8.40 þ 4.98 ug/mL, and 6.78 þ 3.98 ug/mL for gastric bypass. All individual samples, either blood or adipose tissue, had a cefazolin concentration above the MIC of 1 ug/mL. Mean subcutaneous and peri-gastric adipose tissue cefazolin concentrations were approximately 10% of the blood concentration. No surgical site infections (SSIs) were reported within 30 days of surgery for all 19 patients. Conclusions: A single dose of 2 g cefazolin administered by IV push within 15 mins of incision provided a cefazolin serum concentration that exceeded the MIC for Staphylococcus aureus. Only about 10% of the cefazolin penetrated adipose tissue, but the cefazolin concentrations in adipose tissue were above the MIC for Staphylococcus aureus during sleeve gastrectomy or gastric bypass surgery. The study results show that high dose of cefazolin (34 grams IV pre-operation), or re-dosing less than 4 hours to maintain protective level of cefazolin in blood and adipose tissue during bariatric surgeries (sleeve gastrectomy, sleeve gastrectomy with other procedures, or gastric bypass) is not indicated.