This study investigates the fluid volume transfused to pediatric ECMO patients via pressure monitoring circuits, an area currently lacking published data or guidelines. Using in vitro experiments with Edwards True Wave transducers and pressure bags, the study measured fluid volumes from passive and active flushing methods. Results showed that maintaining patency with a pressurized IV bag can transfuse approximately 319.6 mL daily, close to a neonate’s total blood volume. Automated syringe pumps, however, significantly reduce this volume to 24 mL per day. The findings suggest the need for further research to establish best practices.