Extracorporeal life support (ECLS) is a reliable method to support pediatric patients with reversible cardiorespiratory failure associated with congenital heart disease, respiratory insufficiency, or after cardiac surgery. In 2010, our institution adopted an infant/pediatric extracorporeal membrane oxygenation (ECMO) circuit that contains a magnetically levitated centrifugal pump, polymethylpentene oxygenator, and shorter tubing length (ECMO II circuit). Our prior circuit contained a nonocclusive roller pump, polypropylene oxygenator, venous compliance chamber, and hemoconcentrator (ECMO I circuit). A retrospective chart review comparing ECMO I and ECMO II daily plasma-free hemoglobin (PFH) values was conducted. We hypothesized that the PFH is similar between the two ECMO circuit groups. We reviewed medical records of children 3 years of age or younger weighing less than 13 kg who required ECLS between January 2008 and February 2012. PFH levels from 18 ECMO II patients were compared with levels in a retrospective group of an equal number of well-matched ECMO I circuit patients. There was no significant difference between ECMO I and ECMO II circuit groups regarding mean time on ECMO, age in days, and weight. There was also no significant difference in the group mean levels of PFH between ECMO I and ECMO II circuits. There was a significant increase in PFH with hours on ECMO (p < .01) within and between both circuit groups (p < .01) and a significantly greater increase in PFH with ECMO hours (p = .0091) in the ECMO I circuit group. Although there was no significant difference in average PFH with the change in ECMO II circuit technology, advancements such as the magnetically levitated blood pump and polymethylpentene gas exchange device has been associated with significantly fewer mechanical component change-outs (p = .0156) and less clots and fibrin build-up in the circuits (p = .0548).