After obtaining written informed consent from parents or guardians, infants and babies scheduled to have elective surgery under routine general anesthesia and are <6 months of age will be included in the study. After the baby receives routine general anesthesia, a small amount of blood, 0.5 ml, will be drawn from a vein when an I.V. is started for the surgery. The largest possible cannula will be placed whenever possible to decrease hemolysis. If a baby has a central line, the blood sample will be drawn from it. If a baby has an existing peripheral I.V., a blood sample will be drawn from the I.V. cannula only if blood is freely running, to avoid hemolysis.