Clinical Scenario
A 68-year-old male with poorly controlled type 2 diabetes and peripheral vascular disease is admitted to the ICU following emergency debridement of a necrotizing soft tissue infection involving his left lower limb. He presents with septic shock: hypotension requiring norepinephrine, high-grade fever, and altered mental status. Blood cultures grow Staphylococcus aureus, and broad-spectrum antibiotics including vancomycin are initiated.
Over the next 24 hours, the patient develops oliguric acute kidney injury, classified as KDIGO Stage III, with rising creatinine and fluid overload which eventually lead to requirement of invasive mechanical ventilation. Renal replacement therapy is initiated using Coupled Plasma Filtration Adsorption (CPFA) to address both renal dysfunction and the overwhelming inflammatory response (see Figure 1).
Figure 1. Coupled Plasma Filtration Adsorption (courtesy: https://mozarcmedical.com)
Despite standard vancomycin dosing (15 mg/kg IV q12h), his trough levels remain persistently subtherapeutic at 7 µg/mL (target: 15–20 µg/mL). Repeat cultures remain positive, and clinical signs of infection persist.
Which of the following mechanisms most likely explains this finding?
