Retrospective Comparative Cohort of Concomitant Piperacillin-Tazobactam and Vancomycin use in Acute Kidney Injury

Purpose: Piperacillin-tazobactam and vancomycin may be used in combination to provide empiric broad spectrum antimicrobial coverage. Piperacillin-tazobactam and vancomycin have been associated with acute kidney injury (AKI) when used independently. Physicians in our hospital system have perceived an increased incidence of AKI with this antibiotic combination, and therefore have begun avoiding their concomitant use. The primary study objective is to determine the incidence of AKI in patients who received concomitant vancomycin and piperacillin-tazobactam compared to those who received both antibiotics without experiencing changes in renal function from baseline. Methods: This is a retrospective comparative cohort study. Patients ages 18-89 years old who received vancomycin and piperacillin-tazobactam at one of the four main hospitals in our network between June 2011 and June 2013 were evaluated for inclusion. Patients with existing renal failure or AKI at admission and patients readmitted within 30 days who again received the study medications and developed AKI were excluded. Patient with an increase in serum creatinine to greater than or equal to 2 mg/dL made up the AKI group. These patients were matched to patients without AKI within 7 days of admission. Secondary objectives include identifying baseline characteristics or concomitant medications that put a patient at greater risk for development of AKI while receiving piperacillin-tazobactam and vancomycin. The time to onset and resolution of AKI and the degree of kidney injury as defined by RIFLE criteria was evaluated in these patients. Descriptive statistics were used to characterize patient demographic information. Clinical characteristics were compared utilizing independent samples t-test, chi-squared analysis or comparable tests for non-parametric data utilizing a significance value of less than 0.05. Results: There were 802 patients evaluated for inclusion, of which 18 cases were identified and matched with controls in a 1:5 ratio. Combined, cases and controls had an average length of stay of 8.15 days. Separately, cases and controls had average lengths of stay of 12.44 days and 7.29 days, respectively. The average age of patients in this study was 59.42 years, with 66 patients (61.1%) being male. Further statistical analysis is pending