Effectiveness of Vancomycin Dosing Guided by Therapeutic Drug Monitoring in Adult Patients Receiving Extracorporeal Membrane Oxygenation

The clinical situation for patients receiving extracorporeal membrane oxygenation (ECMO) is complex, and drug dosing is complicated by significant pharmacokinetic alterations. We sought to describe the frequency of achievement of therapeutic vancomycin concentrations in critically ill patients receiving ECMO with therapeutic drug monitoring (TDM). In this retrospective observational study, we included all critically ill patients receiving TDM for vancomycin while on ECMO. The primary outcome was the proportion of plasma vancomycin concentrations in the therapeutic range (15 to 20 mg/liter). Factors associated with not achieving therapeutic concentrations were investigated, including ECMO duration and use of renal replacement therapies. Vancomycin TDM was performed for 77 of 116 (66%) patients on ECMO. Median (interquartile range) duration of ECMO support was 7 days (4 to 16 days). The proportion of measurements in the therapeutic range (15 to 20 mg/liter) was 24%, while 46% were subtherapeutic (<15 mg/liter) and 30% were supratherapeutic (>20 mg/liter). The proportion of measures in the therapeutic range was significantly higher on ECMO days for 6 to 13 (incidence rate ratio [IRR], 2.4; 95% confidence interval [CI], 1.2 to 4.6; P = 0.01). Supratherapeutic concentrations were more frequently observed in patients on renal replacement therapy (RRT) (IRR, 2.0; 95% CI, 1.3 to 3.1; P = 0.002). The vancomycin concentrations in patients did not vary with age, gender, or type of ECMO support. Patients receiving vancomycin had suboptimal concentrations early in the course of ECMO. Patients not receiving RRT and those with mild to moderate acute kidney injury (AKI) were at a risk of underdosing, while those with established AKI on RRT were likelier to experience supratherapeutic concentrations.