The Impact of Age-dependent Haptoglobin Deficiency on Plasma Free Hemoglobin Levels During Extracorporeal Membrane Oxygenation Support

Inclusion Criteria: * ECMO group - Thirty critically-ill children (age newborn to 18 years) who are intubated and supported by ECMO. We will target enrollment of 15 subjects less than 12 months of age (with at least 10 subjects enrolled less than 6 months of age) and 15 subjects over 12 months of age. These targets are set to address the secondary aim in the context of normal adult-level haptoglobin concentrations reportedly achieved by 6-12 months of age. * Age-matched control group - Sixty critically-ill children (age newborn to 18 years) who are intubated with acute respiratory failure due to any cause and not supported by ECMO. Two control subjects will be enrolled for every 1 experimental ECMO subject. Age-matching will be performed by the following age groups: * Neonates 37-40 weeks gestation * Neonates 40-42 weeks gestation * Neonates 42-44 weeks gestation * Neonates 44-46 weeks gestation * Neonates 46-48 weeks gestation * Infants 2-4 months of age * Infants 4-6 months of age * Infants 6-12 months of age * Children 1-4 years of age * Children 4-8 years of age * Children 8-12 years of age * Children 12-18 years of age Age-matched control subjects will proceed through the 3 total blood sample collections even if endotracheal extubation occurs within the 3 days of study participation. Age-matching is intended to collect a sample population comparable to the ECMO subject population. We will not match to gender. Exclusion Criteria (both groups, ECMO and age-matched controls): * Personal or family history of thrombotic, hemorrhagic, or hemolytic disease. * Personal history of hematologic malignancy. * Premature neonates less than 37-weeks gestation and/or less than 2 kg in weight. * Infection will not be an excluding factor for either subject group.