Measurement and Calculation of the Extracorporeal Elimination of Vancomycin During Continuous Venovenous Hemodiafiltration and Continuous Venovenous Hemofiltration in Critically Ill Patients

Six surgical intensive care patients with continuous renal replacement therapy and therapy with vancomycin entered the prospective clinical study. The first day the patients were treated with continuous venovenous hemodiafiltration (CVVHDF) and the second day with continuous venovenous hemofiltration (CVVH). Three patients received 500 mg and three patients received 1000 mg of vancomycin every 12 hours. Monoclonal fluorescence polarization immunoassay (AxSYM) of vancomycin levels was performed from serum and dialysate/ultrafiltrate (during CVVHDF) or ultrafiltrate (during CVVH). Blood flow was 90 ml/hr, substitution 1 L/hr predilution, dialysate flow 1 L/hr (CVVHDF). The extracorporeal elimination of vancomycin during CVVHDF and CVVH is nearly linear but shows wide interindividual variation. The extracorporeal clearance of vancomycin was 24.2 ± 3.1 ml/min during CVVHDF (total clearance 60.4 ±18.1 ml/min) and 14.5 ± 2.4 ml/min during CVVH (total clearance 50.2 ± 14.9 ml/min). Intraindividual comparison revealed a significantly higher elimination of vancomycin by CVVHDF (p < 0.028). Peak serum vancomycin levels in patients receiving vancomycin 1g/day were 24.7 ± 5.3 μg/ml (CVVH) and 23.1 ± 5.2 μg/ml (CVVHDF), and with 2 g/day were 33.5 ± 2.7 μg/ml (CVVH) and 27.3 ±4.1 μg/ml (CVVHDF). The daily excreted amount of vancomycin during CVVHDF (r2 = 0.950, p = 0.01) and CVVH (r2 = 0.947, p = 0.01) can be calculated from a vancomycin level in the ultrafiltrate/dialysate outlet (CVVHDF) or the ultrafiltrate (CVVH) 8 hours after dosing. The 8-hour concentration of vancomycin in the ultrafiltrate from CVVH (or ultrafiltrate/dialysate from CVVHDF) during continuous renal replacement therapy serves as a basis for predicting extracorporeal elimination within 24 hours for the individual patient. Since critically ill patients show wide interindividual and intraindividual differences in the volume of distribution, clearance, and elimination half-life of vancomycin during therapy, the estimation of serum levels remains a necessity.