The transition from veno-arterial extracorporeal membrane oxygenation (VA-ECMO) to cardiopulmonary bypass (CPB) presents unique logistical and physiological challenges in pediatric cardiac surgery. In their 2025 publication in the Journal of ExtraCorporeal Technology, Zalfa, Duncan, and Kerins describe an innovative single-circuit technique that enables seamless conversion from ECMO to CPB by incorporating a cardiotomy reservoir into the existing ECMO system . This strategy is particularly relevant for neonates and infants with congenital heart disease who require surgical intervention while already supported on ECMO.
ECMO has long served as a lifesaving modality for pediatric patients experiencing cardiac or respiratory failure. In congenital heart disease, VA-ECMO may function as a bridge to recovery, transplantation, or definitive surgical repair. However, when operative correction becomes necessary, ECMO alone lacks key features required for safe and effective cardiac surgery. Unlike CPB, ECMO circuits do not typically include a cardiotomy reservoir or suction capability, both of which are critical for aspirating shed blood, decompressing the heart, and managing volume shifts during deep hypothermic circulatory arrest (DHCA).
Traditionally, transitioning from ECMO to CPB involves switching to an entirely separate bypass circuit. While effective, this approach introduces additional prime volume—often approximately 250 mL in pediatric circuits—which can equal or exceed a neonate’s circulating blood volume. The result is significant hemodilution, increased exposure to donor blood products, and amplified inflammatory response due to contact with foreign surfaces. These risks are not trivial; transfusion exposure has been associated with infection, prolonged ventilation, and increased morbidity.
To address these concerns, the authors developed a method that preserves the original ECMO circuit while adding a cardiotomy reservoir component intraoperatively. Their ECMO setup utilized a Maquet BioLine coated circuit with an AMG PMP Infant Oxygenator mounted on a Sorin S5 heart-lung machine. Once the decision for surgery was made, a separate cardiotomy reservoir assembly was prepared using a Terumo Capiox FX05 oxygenator (with the oxygenator removed), tubing connectors, and a recirculation line. The reservoir was primed with fresh whole blood (FWB) or reconstituted whole blood (RWB), along with heparin and sodium bicarbonate.
In the operating room, after a formal time-out and sterile preparation, the ECMO circuit was briefly interrupted—typically for 10 to 20 seconds. The venous limb was clamped and divided, and the cardiotomy reservoir was spliced into the circuit using wet-to-wet connections. Once secured, clamps were released and forward flow reestablished, effectively converting the ECMO system into a functional CPB circuit. A heater-cooler was integrated for temperature management, and standard bypass procedures were conducted thereafter.
The study included seven pediatric patients undergoing eight ECMO-to-CPB conversions. The mean age was 88 days, with a median weight of 3.4 kg and mean body surface area of 0.23 m². Diagnoses included Tetralogy of Fallot, Truncus Arteriosus, Total Anomalous Pulmonary Venous Connection (TAPVC), and Aortic Arch Hypoplasia with Atrioventricular Canal. All patients were successfully decannulated from ECMO or CPB support.
Operative outcomes were notable. Mean pre-CPB hematocrit was 37.9%, with a nadir of 31.1% during CPB and recovery to 40.1% post-bypass. Mean blood product utilization was 238 mL. Median CPB time was 97 minutes, with three procedures requiring aortic cross-clamping and DHCA. Despite the complexity of these cases—including extended bypass times up to 336 minutes—the technique was implemented without reported circuit failure or major technical complication.
A major contributing factor to the success of this approach was the institutional use of FWB or RWB for priming. Fresh whole blood provides balanced components—red blood cells, plasma, and platelets—while RWB mimics this composition. By using these products routinely, the team avoided additional hemofiltration or component therapy adjustments during the transition. Furthermore, unused primed blood could be salvaged for postoperative reinfusion, minimizing waste and donor exposure.
Importantly, the design allows flexibility. If conversion back to ECMO is required, the recirculation line enables rapid reconfiguration without full circuit replacement. However, the authors emphasize that this method should not be used if there is suspicion of circuit thrombosis or oxygenator dysfunction. Vigilant monitoring remains essential.
The study is limited by its small sample size and lack of a control group undergoing standard circuit exchange. As such, while feasibility and short-term success are demonstrated, comparative effectiveness in reducing transfusion requirements or inflammatory markers remains to be proven. Larger, multicenter studies would be required to establish superiority over conventional methods.
Nonetheless, this single-circuit ECMO-to-CPB transition represents an elegant solution to a complex clinical challenge. By minimizing prime volume, preserving circulating blood, reducing foreign surface exposure, and maintaining full CPB functionality, this approach aligns with modern principles of blood conservation and pediatric perfusion safety.
For pediatric cardiac surgeons, perfusionists, and ECMO specialists, this technique offers a practical and potentially safer method for managing congenital heart patients requiring operative intervention while on extracorporeal support.
