**6. Conclusion**

The predictive equations currently in use are unacceptable to measure VO2 in ventilated children with congenital heart disease, particularly in those younger than 3 years of age, and in the early postoperative period after CPB. Direct, continuous, and precise measurement of VO2 is fundamental for accurate assessments of hemodynamics and oxygen transport in children undergoing cardiac catheterization and in the ICU after cardiac surgery. Respiratory mass spectrometry is the 'state-of-the-art' method, allowing highly sensitive and precise measurement of VO2. Measured VO2 and the Fick principle allow the calculation of each parameter of systemic hemodynamic and oxygen transport, in varied circulations in congenital heart defects, both before and after complete surgical repair or palliation. These actual measurements are not only useful in clinical management, but important for bedside physiological studies on the balance of systemic oxygen transport in children after CPB. Some routine treatments in current use are intended to improve the balance of oxygen transport, but may actually worsen it. When considering clinical management of unbalanced oxygen transport, clinicians should choose therapies that address both decreased DO2 and increased VO2. ICU management strategies need to be refined to optimize the balance of systemic oxygen transport in children with congenital heart defects undergoing cardiac surgery. The resultant improved clinical outcomes in the early postoperative period and at long term follow-up will improve the quality of life for these vulnerable children.
