Plasma and cerebrospinal fluid population pharmacokinetics of vancomycin in postoperative neurosurgical patients after combined intravenous and intraventricular administration

Combined intravenous and intraventricular administration of vancomycin into the cerebrospinal fluid (CSF) has been increasingly utilized for neurosurgical patients, but little is known about the population pharmacokinetics of vancomycin in the plasma and CSF. The aim of our study was to identify significant factors associated with plasma and CSF vancomycin concentrations to guide clinicians with vancomycin dosing. Patients with an indwelling ventricular drainage catheter who received intravenous and intraventricular vancomycin were enrolled in this study. Blood and CSF samples were collected at scheduled times and vancomycin concentrations determined. A three-compartmental model (central, peripheral and CSF compartments) was proposed to describe the in vivo behavior of vancomycin. CSF outflow resulted in vancomycin loss, and the clearance of CSF compartment (CLCSF) was used to describe this loss. The nonlinear mixed-effects modeling method was applied to structure the population model, and the stepwise incorporation of seven covariates into the final model was attempted. Simulation was performed with the goal of CSF concentrations reaching or exceeding the minimum inhibitory concentration during therapy. Serum creatinine clearance had a significant influence on clearance of the central compartment. CLCSF had a positive correlation with drainage amount and a negative correlation with elapsed time. Model validation (bootstrap and visual predictive check) demonstrated the stability and performance of the proposed population model. A simple-to-use dosage regimen table was created based on the simulation results. The proposed final model may be used to guide clinicians with vancomycin dosing in this specific patient population.