2025 Southeastern Residency Conference

Impact of Extracorporeal Membrane Oxygenation (ECMO) Circuit Age on Vancomycin Dosing Requirements in Critically Ill Patients 
 
Authors: Hope Elrod, Kathleen Jerguson, Erin Massarello 
Background: 
Extracorporeal Membrane Oxygenation (ECMO) alters drug pharmacokinetics, particularly in the early phase (<96 hours), when drug sequestration onto the circuit can lead to lower circulating concentrations. Over time, the formation of a biofilm may reduce sequestration, potentially altering dosing needs. Understanding how ECMO circuit age affects vancomycin dosing is critical for optimizing therapy in critically ill patients. This study evaluates the impact of ECMO circuit age on vancomycin dosing and therapeutic target attainment. 
Methods: 
This retrospective, observational study included critically ill patients at Wellstar Kennestone Regional Medical Center who received IV vancomycin while on ECMO from January 1, 2016, to July 31, 2024. Patients were categorized into early (<96 hours) and late (≥96 hours) ECMO groups. The primary outcome was the difference in mg/kg/day dosing required to achieve therapeutic vancomycin troughs. Secondary outcomes included the proportion of patients achieving therapeutic troughs and the impact of patient demographics, renal function, and loading dose strategies on dosing requirements. CRRT patients were excluded due to potential for additional drug sequestration. Mg/kg dosing was calculated using actual body weight unless the patient was >120% of ideal body weight, in which case adjusted body weight was used. Descriptive statistics were utilized and statistical analyses included chi-square tests, Fisher’s exact tests, and logistic regression. 
Results: 
Sixty patients were included (30 per group). Patients in the early circuit ECMO group received an actual mg/kg/day vancomycin dose of 42.95 compared to 44.21 in the late circuit group. To achieve an extrapolated therapeutic trough of 15 mcg/mL, the mg/kg/day dose was significantly higher in the early circuit compared to the late circuit group (52.58 mg/kg/day vs. 41.21 mg/kg/day, p = 0.019).  
Among patients who received a loading dose, the mg/kg/day dosing required to reach a therapeutic trough was also significantly higher in the early circuit group compared to the late circuit group (56.6 vs. 36.9 mg/kg/day, p = 0.0168). Patients who did not receive a loading dose had no significant difference in dosing requirements between early and late ECMO phases. Likewise, there were no statistically significant differences in dosing between those who received a loading dose and those who did not. 
Mortality was higher in the late ECMO group (χ² = 7.117, p = 0.0074), while differences in therapeutic trough attainment (p = 0.091) and loading vs. no-loading groups (p = 0.5731) were not significant between groups. Logistic regression found that vancomycin duration (p = 0.016) and early versus late circuit ECMO (p = 0.0019) were statistically significant factors influencing initial vancomycin trough levels. 
Conclusions:
Patients initiated on vancomycin within the first 96 hours of ECMO required significantly higher doses to achieve therapeutic levels compared to those started later. The impact was most pronounced in patients who received a loading dose, suggesting that aggressive initial dosing may be necessary in the early ECMO phase. These findings highlight the importance of close therapeutic drug monitoring and tailored dosing strategies to optimize vancomycin therapy in ECMO patients.