title: Association between Pre-Operative Cefazolin Dose and Surgical Site Infection in Obese Patients.
abstract: BACKGROUND
  A fixed dose of cefazolin results in serum concentrations that decrease as body mass increases. Current national guidelines suggest a pre-operative cefazolin dose of two grams may be insufficient for patients ≥120 kg; thus a three gram dose is recommended. These recommendations, however, are based on pharmacokinetic rather than outcome data. We evaluate the efficacy of pre-operative cefazolin two gram and three gram doses as measured by the rate of surgical site infection (SSI).
  
  
  METHODS
  We conducted a retrospective review of adult patients ≥100 kg who were prescribed cefazolin as surgical prophylaxis between September 1, 2012 and May 31, 2013 at an academic medical center. Patients were excluded if cefazolin was prescribed but not administered, had a known infection at the site of surgery, or inappropriately received cefazolin prophylaxis based on surgical indication. The SSIs were identified by documentation of SSI in the medical record or findings consistent with the standard Centers for Disease Control and Prevention definition. Inpatient and outpatient records up to 90 days post-operative were reviewed for delayed SSI.
  
  
  RESULTS
  Four hundred eighty-three surgical cases were identified in which pre-operative cefazolin was prescribed. Forty-seven patients were excluded leaving a total of 436 patients for final analysis: 152 in the cefazolin two gram group and 284 in the three gram group. Baseline demographics were similar between groups with a mean follow-up duration of 77 days for both groups. Unadjusted SSI rates were 7.2% and 7.4% (odds ratio [OR] 0.98, p = 0.95), for the two gram and three gram groups, respectively. When differences in follow-up between groups were considered and logistic regression was adjusted with propensity score, there remained no difference in SSI rates (OR 0.87, 95% confidence interval 0.36-2.06, p = 0.77).
  
  
  CONCLUSIONS
  In otherwise similar obese surgical patients weighing ≥100 kg, the administration of a pre-operative cefazolin two gram dose is associated with a similar rate of SSI compared with patients who received a three gram dose.
authors.affiliation: 1 Department of Pharmacy, Froedtert & the Medical College of Wisconsin , Milwaukee, Wisconsin.|2 Department of Surgery, Division of Trauma and Critical Care, The Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: William J
authors.initials: WJ
authors.lastname: Peppard
authors.affiliation: 1 Department of Pharmacy, Froedtert & the Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: David G
authors.initials: DG
authors.lastname: Eberle
authors.affiliation: 2 Department of Surgery, Division of Trauma and Critical Care, The Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Kugler
authors.affiliation: 1 Department of Pharmacy, Froedtert & the Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Mabrey
authors.affiliation: 2 Department of Surgery, Division of Trauma and Critical Care, The Medical College of Wisconsin , Milwaukee, Wisconsin.
authors.forename: John A
authors.initials: JA
authors.lastname: Weigelt
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019072:Antibiotic Prophylaxis; D002437:Cefazolin / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D013530:Surgical Wound Infection / Q000150:complications / Q000188:drug therapy / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D000900:Anti-Bacterial Agents; D002437:Cefazolin
keywords: cefazolin; pharmacokinetics; surgical site infection