(975) Levofloxacin Drug Monitoring in Continuous Venovenous Hemodiafiltration for Legionella Pneumonia

Introduction: Critically ill patients may require continuous renal replacement therapy (CRRT) due to acute kidney injury. RRT introduces various challenges on antimicrobial delivery, potentially requiring dose adjustments to reach therapeutic drug concentrations. Current pharmacokinetic (PK)/pharmacodynamic (PD) data evaluating the use of levofloxacin in critically ill patients receiving CRRT suggests that conventional dosing fails to achieve PD targets.

Description: A 79 year-old male with past medical history including ischemic cardiomyopathy and chronic kidney disease was admitted with one-week of dyspnea. Computed tomography of the chest revealed multifocal bilateral consolidations consistent with pneumonia; thus, the patient was started on empiric CAP treatment with piperacillin-tazobactam and azithromycin. The patient developed acute respiratory distress syndrome requiring intubation. Bronchoscopy with bronchoalveolar lavage resulted with positive Legionella PCR. Azithromycin was changed to levofloxacin 750 mg IV every 48 hours given lack of clinical improvement. The next day, the patient was started on continuous venovenous hemodiafiltration (CVVHDF) with a total effluent fluid rate of 3 L/hr and the levofloxacin dose was increased to 750 mg every 24 hours. Azithromycin 500 mg IV every 24 hours was re-initiated after four days of levofloxacin given concern for clinical failure with levofloxacin monotherapy in patients on CRRT. Respiratory cultures from the day after admission grew Legionella pneumophilia one week later. Levofloxacin peak and trough levels were ordered surrounding the fifth dose, representing steady state given minimal interruptions to CRRT. Serum levels obtained 2.5 hours and 24 hours post-dose resulted at 11.54 mcg/mL and 4.22 mcg/mL; the peak level falls within goal range for indication of 8-12 mcg/mL. Levofloxacin monotherapy continued following cessation of CRRT. The patient ultimately required tracheostomy for persistent ARDS and expired due to other medical issues.

Discussion: This is the first reported case of target PD attainment with conventional levofloxacin dosing on CRRT. This case highlights the importance of therapeutic drug monitoring and displays the interpatient variability often seen in critically ill patients.