A novel configuration for providing continuous renal replacement therapy via the ECMO circuit in VV ECMO without alarm adjustment

Abstract

Background It is common for patients on venovenous extracorporeal membrane oxygenation (VV ECMO) to require continuous renal replacement therapy (CRRT). This can be done using separate vascular access for the CRRT circuit, by placing the CRRT hemofilter within the ECMO circuit, or through a separate CRRT circuit connected to the ECMO circuit. When a CRRT circuit is connected to the ECMO circuit, the inflow and outflow CRRT limbs can both be placed pre-ECMO pump or the CRRT circuit can span the ECMO pump, with the CRRT inflow post-ECMO pump and the outflow pre-ECMO pump. Both configurations require the CRRT alarms to be inactivated due to high positive pressure experienced post-pump and low negative pressure pre-pump. We describe a novel technique that does not require separate venous access and still allows the CRRT alarms to be activated. Technique The CRRT inflow line is connected to the post-oxygenator de-airing port. The CRRT outflow line is connected to the pre-pump side of the ECMO circuit. Pigtails allow for these connections and act as resistors negating the large range of pressures generated by the ECMO centrifugal pump. Results We implemented this configuration in 11 patients with 100% success rate allowing for alarms to be maintained in all patients. The median number of interruptions per 100 CRRT days was 11.7. The median CRRT filter lifespan was 2.2 days, and the average blood flow was maintained at 311 mL/min. Conclusions This configuration allows for efficient use of CRRT in ECMO patients while maintaining the safety alarms on the CRRT machine.