Selection of Prophylactic Antimicrobial Agent May Affect Incidence of Infection in Small Bowel and Colorectal Surgery

Abstract

Antibiotic prophylaxis guidelines suggest single-dose regimens are adequate, but comparisons of multiple agents are lacking. We compared post-operative infection rates retrospectively among six common prophylactic agents given as a single dose to colorectal surgery patients. A commercial database supplied demographics, All-Patient Refined Diagnosis-Related Groups (APR DRGs), International Classification of Disease (ICD)-9 codes, and drug utilization information for patients discharged from 303 hospitals from January 2007-December 2008 whose charts had been sampled for reporting Surgical Care Improvement Project (SCIP) measures. The patients (n=4,634) had the same APR DRG, no baseline infection, and prophylaxis discontinued within 24 h of surgery. Development of infection was determined by ICD-9 code. "Single dose" was defined as ≤3 g of ampicillin-sulbactam (AMP); ≤2 g of cefotetan (CFT), cefoxitin (FOX), or ertapenem (ERT); or metronidazole and ≤2 g of cefazolin (CFZ) or ≤750 mg of levofloxacin (LVX) given on the day of the procedure. Multivariable logistic regression evaluated factors associated with infection, including agent choice. Frequency of use and rate of infection (3.7% overall) were FOX 1,752 (4.9%), ERT 1,166 (2.7%), CFZ 549 (2.7%), AMP 447 (3.6%), LVX 402 (3.2%), and CFT 318 (3.5%). The unadjusted infection rate differed by agent (p=0.037). Multiple regression analysis found infection to be associated significantly with increasing APR DRG severity, longer procedures, younger age, and male gender (p<0.01 for each except p=0.02 for age), as well as agent choice. Among agents (vs. FOX as reference), ERT was associated with a lower infection rate (odds ratio 0.53; 95% confidence interval 0.34-0.82; p<0.01); the odds ratio for all other agents contained the value 1.0. Agent selection among prophylactic antibiotics is one of many factors associated with infection development in colorectal surgery patients.