Radical-7 (Masimo corporation, Irvine, CA) is a device that operates using the principle of co-oximetry . Radical-7 had been validated in various clinical purposes. Measurement of blood hemoglobin is an important application for Radical-7 device. Non-invasive hemoglobin (Sp-Hb) measurement has been frequently validated in adults; as well as in pediatric patients; however, its accuracy in children with congenital heart disease was not investigated. Congenital heart disease infants usually undergo major operations and frequently need transfusion of blood. Moreover, these patients have special circulatory physiology that might impact the device accuracy. It had been recently reported that the performance of co-oximetry in congenital heart disease children is poor in measurement of oxygen saturation specially at oxygen saturation under 75%; however, its accuracy in measurement of hemoglobin was not investigated yet. In this study, the investigators will evaluate the accuracy of Sp-Hb compared to traditional Lab-Hb in children with congenital heart disease. the investigators will also compare the accuracy of Sp-Hb in cyanotic children to acyanotic children.