Relationship between plasma polymyxin B concentrations and acute kidney injury in critically ill elderly patients: Findings from a prospective study.

Abstract

Objective: The objective of this study was to determine the relationship between the plasma polymyxin B concentration and renal function in elderly patients.

Methods: This prospective, case-control, observational study included elderly patients who received polymyxin B therapy and were divided into an acute kidney injury (AKI) group and a non-AKI group based on their renal function. We monitored the pharmacokinetics and pharmacodynamics of polymyxin B, including the minimum plasma concentration (C_min), mean blood drug concentration at steady state (C_ss,avg), and area under the concentration-time curve across 24 h at steady state (AUC_ss,24h) in both study groups. The plasma polymyxin concentration was determined using high-performance liquid chromatography-tandem mass spectrometry.

Results: The loading doses, C_min, C_ss,avg, and AUC_ss,24h were significantly higher in the AKI group than in the non-AKI group (p < 0.05). Receiver-operating characteristic curve analysis showed that the optimal cutoff values for predicting AKI were 2.94 mg/L for C_min, 4.14 mg/L for C_ss,avg, and 99.35 mg·h/L for AUC_ss,24h, with corresponding sensitivities and specificities ranging from 78.57% to 82.14%.

Conclusion: Monitoring plasma polymyxin B concentrations is essential in elderly patients. Keeping the C_min below 2.94 mg/L, the C_ss,avg below 4.14 mg/L, and the AUC_ss,24h below 99.35 mg h/L may help prevent AKI in this population.