In this episode, I’ll discuss an article about the impact of total body weight on rate of acute kidney injury in patients treated with piperacillin–tazobactam and vancomycin
Lead author: W. Cliff Rutter
Published in American Journal of Health System Pharmacy August 2019
Many studies have demonstrated a link between the combination of piperacillin–tazobactam and vancomycin and increased rates of acute kidney injury (AKI). Previous studies have also demonstrated an association between increased body size and AKI rates with vancomycin and other antimicrobials. The authors of this study sought to evaluate a large sample of patients to determine whether obesity is associated with acute kidney injury (AKI) among patients receiving combination therapy with piperacillin–tazobactam and vancomycin.
The study was a retrospective, single-center cohort of patients who received combination therapy for at least 48 hours with vancomycin and piperacillin-tazobactam. Notable exclusion criteria were: patients with chronic kidney disease, baseline creatinine clearance of less than 30 mL/min, or cystic fibrosis. In addition, patients were not included in the analysis if height or weight data was missing.
The cohort was composed of over 8000 patients. Total bodyweight of 91 kg or more was the variable most predictive of AKI. Patients in this weight category were also statistically significantly more likely than lower-weight patients to have diabetes (39% versus 21%), hypertension (64% versus 47%), or heart failure (15% versus 13%).
Not surprisingly, the group of patients with a lower body weight received significantly less vancomycin. The median daily dose for patients under 91 kg was 2g and the median daily dose in the higher weight group was 3g.
The rate of AKI was higher in the group of patients that weighed 91 kg or more by an absolute difference of 6% and a relative difference of 33%. This difference was statistically significant with an adjusted odds ratio of 1.46.
The authors concluded:
Increased total body weight increased the rate of AKI among patients concurrently treated with piperacillin–tazobactam and vancomycin independent of clinically important confounders, with an important breakpoint occurring at 91 kg.
Even though this was a single-center study, its large size and broad population help strengthen its generalizability. Just under 1600 patients in this cohort developed AKI, which is far beyond that of other studies.
There was a smaller percentage (15%) of patients in this study compared to others that were cared for in the ICU. The authors surmise this is why the rate of AKI was only about 20% in this study whereas previous studies had a rate of about 30% with concomitant vancomycin and piperacillin–tazobactam use.
In patients that weigh 91 kg or greater, it would seem the combination of vancomycin and piperacillin-tazobactam should only be used if the benefit outweighs the risk. In most cases that do not include multiple allergies or drug resistances, alternative antibiotics are available to avoid this combination.
To get access to my free download area with 20 different resources to help hospital pharmacists in their practice go to pharmacyjoe.com/free.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.