(870) Detectable Concentrations With Inhaled Tobramycin in Critically Ill Infants and Children

Introduction: In a pilot study at our institution 50% of critically-ill children without cystic fibrosis (CF) receiving inhaled tobramycin had a detectable concentration (>0.5 mcg/mL) with three patients developing acute kidney injury (AKI). The purpose of this study was to describe the incidence of detectable concentrations and clinical characteristics of critically-ill children receiving inhaled tobramycin utilizing a standardized protocol with a dose of 300 mg twice daily.

Methods: This was single-center retrospective study of critically-ill children < 18 years without CF receiving inhaled tobramycin between 7/1/2016-8/31/2021. Data collection included demographics, tobramycin regimen, and renal function. The primary objective was to determine the incidence of detectable tobramycin trough concentrations >0.5 mcg/mL. Secondary objectives included a comparison of clinical characteristics between those with and without detectable concentrations and identification of patients with AKI defined by the Kidney Diseases Improving Global Outcomes (KDIGO) criteria. Analysis was performed using SAS 9.4, with a p-value < 0.05, and a multivariate regression model was performed to identify factors for detectable concentrations and AKI.

Results: Forty-four patients (66 courses) were included. Thirty (68%) patients had detectable concentrations and 7 (16%) developed AKI. No significant differences in demographics, diagnosis, mechanical ventilation settings, and number of nephrotoxins were noted between those with and without detectable concentrations or AKI. In a multivariable regression model assessing factors associated with detectable concentrations, the only factor associated was days of mechanical ventilation [odds ratio (OR) 0.99 (95% CI: 0.99-1.0; p=0.043)]. Of the 7 patients that developed AKI, three patients had a detectable tobramycin concentration. No variables in the multivariable regression were associated with the development of AKI.

Conclusions: Detectable concentrations occurred with the majority of courses, with AKI associated with < 15% of courses. Clinicians should consider utilizing trough monitoring for all mechanically ventilated critically-ill children receiving inhaled tobramycin.