Blue baby syndrome
Blue baby syndrome can refer to a number of conditions that affect oxygen transportation in the blood, resulting in blueness of the skin in babies. Historically, the term "blue baby syndrome" has referred to babies with one of two conditions:
- Cyanotic heart disease, which is a category of congenital heart defect that results in low levels of oxygen in the blood. This can be caused by either reduced blood flow to the lungs or mixing of oxygenated and deoxygenated blood.
- Methemoglobinemia, which is a disease defined by high levels of methemoglobin in the blood. Increased levels of methemoglobin prevent oxygen from being released into the tissues and result in hypoxemia.
Causes
Cyanotic heart disease
Specific types of congenital heart defects that cause blood to pass directly from the right side of the heart to the left side result in cyanosis. In these defects, some of the blood that is pumped to the body has not been oxygenated by the lungs and therefore will appear more blue. Infants with these types of heart defects may have a constant bluish tint to their skin, or they may have temporary episodes of cyanosis. The degree of cyanosis is dependent on how much deoxygenated blood is mixed with oxygenated blood before being pumped to the body.The five most common cyanotic heart defects that may result in Blue Baby Syndrome include the following:
| Pathology | Brief Description | Epidemiology | Diagram |
| 1. Persistent truncus arteriosus | Instead of two separate major blood vessels leaving the heart, there is one common outgoing vessel. | 3-5/100,000 births | |
| 2. Transposition of the great vessels | The positions of the pulmonary artery and the aorta are switched, with the aorta connecting to the right ventricle and the pulmonary artery connecting to the left ventricle. | 1-5/10,000 births | |
| 3. Tricuspid atresia | The heart valve connecting the right atrium to the right ventricle does not form properly, disrupting blood flow in the heart. | 1-9/100,000 births | |
| 4. Tetralogy of Fallot | A heart defect with 4 features including a narrow pulmonary artery, a thick right ventricle, an aorta that connects to both the right and left ventricles, and a hole in the ventricular wall. | 1-5/10,000 births | |
| 5. Anomalous pulmonary venous connection | The pulmonary veins returning oxygenated blood from the lungs do not connect properly to the heart. | 6-12/100,000 births |
Methemoglobinemia
Blue baby syndrome can also be caused by methemoglobinemia, either due to a hereditary or acquired condition. Congenital methemoglobinemia is typically caused by an inherited deficiency in the enzyme NADH-cytochrome b5 reductase, which is responsible for reducing methemoglobin in the blood. Methemoglobinemia can be acquired in infancy from a number of exposures, including certain drugs or nitrates in drinking water. Nitrates from polluted drinking water form compounds in the body that change haemoglobin to methemoglobin, decreasing the ability of blood to carry oxygen. In infants, the condition can be fatal. The sources of nitrate can include fertilizers used in agricultural lands, waste dumps or pit latrines. For example, cases of blue baby syndrome have been reported in villages in Romania and Bulgaria, and were thought to be caused by groundwater polluted by nitrate leaching from pit latrines. Nitrate levels are subject to monitoring to comply with drinking water quality standards in the United States and other countries. The link between blue baby syndrome and nitrates in drinking water is widely accepted, but some studies indicate that other contaminants, or dietary nitrate sources, may also play a role in the syndrome.Other causes
Other problems in neonates, such as respiratory distress syndrome, can also produce temporary cyanosis. Like methemoglobinemia, these are not structural lesions and are not regarded by most doctors as true "cyanotic lesions."Diagnosis
Symptoms of blue baby syndrome are often subtle. Cyanosis can be noted in babies around the lips, tongue, and sublingual area, where the skin is thinnest. If cyanosis is suspected, pulse oximetry can used to measure oxygen saturation in the blood. While severe cyanosis can be easily noticed, an oxygen saturation as low as 80% causes only mild clinical cyanosis that is difficult to see.Babies with cyanosis due to congenital heart disease usually present with symptoms hours to days after birth. In addition to cyanosis, they often show signs of tachypnea, a heart murmur, and decreased peripheral pulses. If congenital heart disease is suspected in a newborn, doctors will likely perform several tests to evaluate the heart, including a chest x-ray, echocardiogram, and electrocardiogram.
Babies with cyanosis due to methemoglobinemia also usually present with cyanosis in the neonatal period, but pulse oximetry may be falsely elevated and does not always reveal low blood oxygen saturation. A co-oximeter can be used to detect levels of methemoglobin in the blood if methemoglobinemia is suspected.