Implementation of an antibiotic nomogram improves postoperative antibiotic utilization and safety in patients undergoing coronary artery bypass grafting

BACKGROUND Routine, initial, empiric vancomycin dosing by clinicians in postoperative coronary artery bypass grafting (CABG) patients was identified as a potential patient safety issue in the Cardiovascular Intensive Care Unit (CVICU) because the rate of postoperative acute renal insufficiency (ARI) and average patient Body Mass Index (BMI) > 35 kg/m2 were significantly higher in our institution than those of the Society of Thoracic Surgeons (STS) database. A vancomycin dosing nomogram was derived from the local patient population in the attempt to improve patient safety by convincing clinicians to use an evidence-based approach to vancomycin prescription. METHODS We analyzed two different treatment strategies that were applied consecutively to an intensive care unit population. CABG patients dosed empirically with vancomycin (group 1, pre-nomogram) were compared with CABG patients dosed using a vancomycin dosing nomogram (group 2, post-nomogram) derived from the hospital population using an Internet program that facilitated creation of a local nomogram. The two groups were analyzed as to age, sex, body mass index, creatinine clearance, and vancomycin dosage using logistic regression and testing for continuous and categorical variables. RESULTS Nomogram use decreased the number of patients receiving the customary dose of one gram every 12 hours in those group 2 patients with diminished CrCl as compared with those in group 1 with diminished CrCl (group 2, 2/21 vs. group 1, 14/21, p < .0001), as well as in those with a normal creatinine clearance, (group 2, 2/15 vs. group 1, 26/34, p < .0001). Therefore, nomogram use affected the customary dose of one g vancomycin every 12 hours between the two groups overall (group 1, 40/55 vs. group 2, 4/36, p < .001), whereby 32/36 (88.9%) of group 2 patients had their dosing altered when compared to what would have been formerly prescribed, p < .0001. Furthermore, nomogram use resulted in fewer doses of antibiotics per year resulting in a cost savings to the hospital with no increase in the rates of infection. CONCLUSION Implementation of the nomogram resulted in a more appropriate antibiotic utilization, regardless of creatinine clearance, that decreased costs without increasing infection rates.