Objective Continuous renal replacement therapy (CRRT) in patients receiving venovenous extracorporeal membrane oxygenation (VV ECMO) can be accessed via separate venous access (SVA) or directly “in-line” within the ECMO circuit. The objective of this study is to compare the efficacy and safety of SVA versus in-line configuration in patients requiring CRRT and VV ECMO.

Design A retrospective review of 16 subjects receiving CRRT while on VV ECMO support.

Setting Adult ICU at a tertiary academic medical institution.

Patients Critically ill adult subjects with severe respiratory failure undergoing percutaneous VV ECMO and CRRT.

Interventions CRRT with venous access via separate temporary hemodialysis catheter versus direct access in-line with the VV ECMO circuit.

Measurements and Results Subject demographics, ECMO cannulation configuration, duration of CRRT, oxygenator and CRRT filter lifespan, number of interruptions, and dialysis blood flow rate were recorded. Five patients received CRRT via SVA and 11 patients via in-line configuration. There was a higher mean number of days on CRRT in the in-line group (7 vs 12 days, p = 0.32). There was no significant difference in oxygenator lifespan (days) (17.1 vs 14.72, p = 0.597), CRRT filter lifespan (days) (1.68 vs 2.15 p = 0.136), or interruptions per 100 CRRT days (10 vs 11.73, p = 0.834) in SVA vs in-line groups. Percentage days with therapeutic anticoagulation (65 vs 68, p =0.859) and initial dialysis blood flow rate (300 vs 310.91 mL/min, p = 0.258) were similar between configurations. SVA was associated with frequent access site manipulation (60% of patients) and catheter site bleeding (40% of patients).

Conclusions CRRT can be delivered via SVA or in-line configuration in patients requiring VV ECMO with similar efficacy. Separate venous access for CRRT may be associated with higher rates of access associated bleeding and need for access manipulation when compared to in-line configuration.