The VPT combination was associated with both an increased AKI risk and a more rapid onset of AKI compared to the VC combination.

Despite their common use as an empirical combination therapy for the better part of a decade, there has been a recent association between combination therapy with vancomycin and piperacillin-tazobactam and high rates of acute kidney injury (AKI). The reasons for this increased association are unclear, and this analysis was designed to investigate the association. Retrospective cohort and case-control studies were performed. The primary objective was to assess if there is an association between extendedinfusion piperacillin-tazobactam in combination with vancomycin and development of AKI. The secondary objectives were to identify risk factors for AKI in patients on the combination, regardless of infusion strategy, and to evaluate the impact of AKI on clinical outcomes. T he combination of vancomycin and piperacillin-tazobactam is a commonly prescribed empirical therapy for patients with health care-associated infections, as it provides coverage against both methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (1). There have been recent reports of relatively high rates of acute kidney injury (AKI), in the range of 15 to 35%, for patients receiving a combination of vancomycin and piperacillin-tazobactam (2-5), which are higher than those reported for patients receiving vancomycin alone (2, 5) and for patients receiving vancomycin and cefepime concomitantly (3). Although vancomycin has long been recognized as a nephrotoxic agent, and piperacillin-tazobactam has been associated with interstitial nephritis, the combination of these agents has been routinely used for many years; however, reports of increased AKI risk have only recently emerged (2-5).The reason for the high rates of AKI in patients receiving vancomycin and piperacillin-tazobactam is unclear, as is the reason for the recent increase in the frequency of reports regarding an association between patients receiving this combination and AKI. Some have hypothesized that the recently reported increased risk is related to more-aggressive vancomycin dosing based on the recently published vancomycin consensus guidelines (6).In addition to the changes in vancomycin dosing, there has also been increased interest in implementing extended-duration infusions of piperacillin-tazobactam in an attempt to optimize the time that free concentrations of the drug are above the MIC of target pathogens, as this is the pharmacokinetic/pharmacodynamic predictor of efficacy. Evidence has been mounting that extended infusion of piperacillin-tazobactam can improve outcomes in patients with invasive infections (7).In 2013, there was an anecdotal increase in cases of AKI among patients receiving vancomycin at the Detroit Medical Center (DMC), Detroit, MI. This perceived increase coincided temporally with a switch of the preferred antipseudomonal agent from cefepime to piperacillin-tazobactam, as well as the implementation of extended-infusion (3-h) administration of all antipseudomonal ␤-lactams (previously administered via standard intermit-

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The impact of the 2013 NHSN CAUTI definition on CAUTI rates was analyzed. A total of 107 CAUTI episodes were identified; 60 according to NHSN 2013 definitions only and 47 according to the 2012 and 2013 definitions. Physician-diagnosed "other infections" were more common among patients who had CAUTI only according to NHSN 2013 definitions (P<.001).