Protein Distribution and Colloid Osmotic Pressure in Children With Volume and Pressure Loading Due to Congenital Heart Defects

This project will evaluate fluid balance and oedema formation in children with the same congenital heart disease (Atrial Septal Defect) who will either go through heart surgery with the use of Cardio Pulmonary Bypass and hypothermia or through interventional catheterization. The investigators will measure interstitial colloid osmotic pressure, distribution of proteins and cytokines. The study hypothesis is that "Oedema developed during heart surgery is caused by reduced colloid osmotic pressure gradient through the capillary membrane".