Tan Tock Seng Hospital1
Continuous renal replacement therapy in the critically ill can alter the pharmacokinetics of vancomycin, resulting in suboptimal vancomycin concentrations and treatment outcomes. This study aims to evaluate vancomycin dosing for patients receiving continuous veno-venous hemodiafiltration (CVVHDF).
This was a retrospective review of patients admitted to intensive care units in TTSH between January 2016 to September 2016. Patients with ≥ 1 vancomycin trough concentration while undergoing CVVHDF were included. Patients who received vancomycin prior to CVVHDF or whose CVVHDF was interrupted for ≥ 6 hours within a 24-hour period were excluded. The primary and secondary outcome was the proportion of patients achieving a therapeutic vancomycin trough concentration (15-20 mg/L) within 24 hours and between 24-48 hours of vancomycin therapy respectively.
11 patients were included in the analysis. The median vancomycin loading dose was 18.9 (IQR: 15.5 – 23.6) mg/kg, and the median maintenance dose was 20.0 (IQR: 16.8-24.5) mg/kg/day. The median dose of CVVHDF was 32.1 (IQR: 30.2 – 34.4) mL/kg/hr.
Only 4 of 11 (36.4%) vancomycin trough concentrations obtained within 12 -24 hours of vancomycin initiation were within therapeutic range. Supratherapeutic concentrations (range: 21-24 mg/L) were observed in 4 patients who continued on vancomycin therapy for 24-48 hours at a median maintenance dose of 22.3 [IQR: 17.4 – 27.4] mg/kg/day.
Most vancomycin trough concentrations were suboptimal while on CVVHDF. The upper limit of the reference maintenance dose range (10mg/kg 12 hourly) may be associated with supratherapeutic vancomycin trough concentrations for patients continuing beyond 24 hours of vancomycin therapy and CVVHDF.