Cyanosis can be classified as central and peripheral, or acrocyanosis. Acrocyanosis is bluish discoloration of the distal extremities and is often benign and normal in the newborn period. Central cyanosis reflects deoxygenated hemoglobin in the blood and is generally detectable when there is >3 g/dL of deoxygenated hemoglobin in arterial blood or >5 g/dL in capillary blood. Frequently the “cyanotic neonate” is diagnosed upon detection of desaturation by pulse oximetry. This chapter focuses on the evaluation and treatment of cardiac causes of cyanosis or desaturation in the newborn. Approximately one out of every five heart defects are “cyanotic” lesions with an estimated prevalence of 16 out of every 10,000 live births.
To provide guidance for neonatologists, pediatricians, advanced practitioners, and nurses on evaluation and treatment of the infant with known or suspected cyanotic congenital heart disease.
The first step in assessing an infant with cyanosis is to determine the mechanism of desaturation. Cyanosis or desaturation associated with heart disease is due to a right-to-left shunt leading to mixing of deoxygenated blood from the venous circulation with the oxygenated blood of the arterial circulation. There are other potential causes of desaturation that may also require evaluation including: 1) respiratory desaturation due to lung disease with ventilation-perfusion mismatch; 2) pulmonary hypertension which causes desaturation when there is a coexisting source of intracardiac shunting (e.g., atrial septal defect, patent ductus arteriosus, or even a patent foramen ovale); 3) central desaturation due to hypoventilation usually secondary to central nervous system depression or injury; and 4) methemoglobinemia, a very rare cause of neonatal cyanosis, due to decreased affinity of hemoglobin for oxygen.
Published guidelines outline indications for fetal echocardiography including:
High-risk maternal factors (e.g., maternal diabetes mellitus, teratogen exposure)
An immediate family history of structural heart defects
Concerns identified on an obstetrics screening ultrasound
Almost half of all cardiac defects requiring surgery within the first 6 months of life (excluding patent ductus arteriosus [PDA]) in the United States are diagnosed prenatally.
Physical examination remains critical to accurately diagnose life-threatening heart disease including identification of central cyanosis and features associated with specific lesions (see below).
Pulse oximetry screening is recommended in the United States and in other nations in term neonates.