Also known as the “blue baby operation,” the Blalock-Taussig procedure is a surgery in which a detour (shunt) is created from a branch of the aorta to the pulmonary artery. The surgery is performed on an infant or child who is born with a congenital heart defect that results in diminished blood flow to the lungs, which in turn causes a lack of oxygen-rich blood circulating through the body. A child born with this kind of defect is sometime referred to as a blue baby because of the bluish tint to the skin, lips and other body parts.

The Blalock-Taussig procedure allows blood to flow from the aorta to the pulmonary artery and to the lungs, where it can be enriched with fresh oxygen. As a result, the level of oxygen in the child’s blood flowing to the body is improved and the child may show less of a blue tint (cyanosis) in various areas of the body, or may even show a fully natural skin tone. The procedure may also improve other symptoms, including fatigue and weakness, which can result from the defect. In addition, the child may demonstrate some improvement in growth and weight gain.

There are a number of heart defects that may require a Blalock-Taussig procedure. For example, the following heart defects interfere with the natural flow of blood from the lower-right chamber of the heart (the right ventricle) through the pulmonary artery and to the lungs, resulting in blood flow that seriously lacks oxygen:

• Tetralogy of Fallot. A condition that involves the “tetralogy” or combination of the following four elements: ventricular septal defect, enlargement (hypertrophy) of the right ventricle, narrowing (stenosis) of the pulmonic valve and a displaced/deviated aorta. These four heart defects lead to reduced blood flow to the lungs, a serious lack of oxygen-rich blood and cyanosis.
  
  
• Pulmonary atresia. A condition in which an infant is born with a completely closed pulmonic valve (the valve between the right ventricle and the pulmonary artery) or is missing a portion of the main pulmonary artery. As a result, blood cannot travel from the right ventricle through the pulmonary artery and to the lungs, resulting in a lack of oxygen-rich blood and cyanosis.
  
  
• Pulmonary stenosis. A condition in which the pulmonic valve is abnormally narrow, interfering with the flow of blood from the right ventricle through the pulmonary artery and to the lungs, resulting in oxygen-deprived blood and cyanosis.
  
  
• Tricuspid atresia. A condition in which an infant is born with a completely closed tricuspid valve (the valve between the right atrium and the right ventricle) and, usually, an undersized or absent right ventricle. As a result, blood cannot travel from the right atrium to the right ventricle, which would have pumped the blood through the pulmonary artery and to the lungs.
  
  
• Tricuspid stenosis. A condition in which the tricuspid valve is narrowed, interfering with the flow of blood from the right atrium to the right ventricle, which would have pumped the blood through the pulmonary artery and to the lungs.
  
  
• Hypoplastic left heart syndrome (HLHS). A condition in which the left side of the heart, including the left ventricle, aortic valve and aorta, is severely underdeveloped. As a result, the left ventricle is unable to pump enough oxygen-rich blood to the body, leading to cyanosis.

The Blalock-Taussig procedure is palliative, meaning that it helps relieve immediate symptoms, rather than reparative, meaning that the problem is repaired. Other surgeries to correct the heart defect itself will usually be performed when the child is stronger.