A Single-Center Evaluation of Extended Infusion Piperacillin/Tazobactam for Empiric Treatment in the Intensive Care Unit.

Background: Piperacillin/tazobactam (PTZ) extended infusion (EI) is often used empirically in the intensive care unit (ICU). Gram-negative (GN) organisms with PTZ minimum inhibitory concentrations (MICs) >16/4 µg/mL are considered intermediate or resistant. Objective: The objective of this study was to evaluate MICs of GN isolates from the ICU to determine whether the hospital protocol for PTZ 3.375 g EI over 4 hours administered every 8 hours is an appropriate empiric regimen for ICU patients and to evaluate patient-specific risk factors associated with elevated MICs. Methods: All ICU patients admitted during 2017 with a confirmed GN organism from a non-urinary source were included for retrospective chart review. Patients with cystic fibrosis or cultures obtained >48 hours prior to ICU admission were excluded. Demographics, GN organism, culture source, risk factors for resistance, susceptibility profile, comorbidities, and creatinine clearance were collected. Appropriateness was defined as PTZ MIC ≤16/4 µg/mL in >80% of isolates. Results: Two hundred and thirty-one patients were included. The average patient was 56 years old. The majority of patients were white (64.1%) and male (69.7%). Pseudomonas aeruginosa (41%) was the most common organism isolated. Overall, 28% of GN isolates had MICs >16/4 µg/mL. Dialysis (P = .01), intravenous antibiotics within 90 days (P < .001), and presence of wounds/trauma (P = .01) were associated with elevated MICs. Conclusion: Current PTZ EI 3.375 g dosing regimens may not provide adequate empiric coverage for some GN organisms in ICU patients, especially for those who have previously received intravenous antibiotics, are on dialysis, or have wounds/trauma.