A Comparison of Separate Access versus In-Line Configuration for Continuous Renal Replacement Therapy in VV ECMO

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. Question Do separate venous access and in-line configuration for continuous renal replacement therapy (CRRT) in patients requiring VV ECMO have different safety and feasibility profiles? Findings: This retrospective review showed 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) between separate venous access and in-line configuration groups. While there was no significant difference in mortality (40% vs 72.73%, p = 0.299), separate venous access was associated with frequent access site manipulation (60% of patients) and catheter site bleeding (40% of patients). Meaning CRRT in patient requiring VV ECMO can be achieved via separate venous access or in-line configuration with similar safety and feasibility specifically regarding oxygenator and filter function. Summary Statement Continuous renal replacement therapy can be delivered via separate venous access or in-line configuration in patients requiring VV ECMO. Both dialysis access configurations display similar efficacy as described by oxygenator and CRRT filter lifespan, number of CRRT interruptions, and dialysis blood flow rates. 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The author(s) received no specific funding for this work. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The retrospective review was approved by Cooper University Hospital Institutional Review Board (IRB# 21-145) on 7/29/2021 under the title “Evaluation of CKRT Configurations During VV-ECMO.” Procedures were followed in accordance with ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975. Informed consent was waived. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Not Applicable Data cannot be shared publicly because of private information. Data are available from the Institutional Data Access / Ethics Committee (contact via email) for researchers who meet the criteria for access to confidential data. * Abbreviations: BFR : blood flow rate BMI : Body mass index CRRT : continuous renal replacement therapy ECMO : extracorporeal membrane oxygenation IQR : interquartile range St dev : standard deviation