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· Cyanosis in the newborn is defined as an arterial saturation <90% and a PO2 <60 torr
· To help differentiate between cardiogenic and non-cardiogenic causes initially obtain an arterial saturation on room air and obtain a subsequent measurements on 100% oxygen
· Infants w/neurogenic or pulmonary causes of cyanosis will demonstrate increases in arterial blood saturation on 100% oxygen while infants with congenital heart disease show minimal elevation
· There are 3 general sources of arterial desaturation in neonates with structural heart disease:
1.) Lesions with decreased pulmonary blood flow (tetralogy of Fallot, severe pulmonary stenosis/atresia, and tricuspid atresia)
2) Admixture lesions, in which desaturated systemic venous blood mixes with intracardiac blood, and then enters the aorta (transposition of great vessels, partial anomalous pulmonary venous drainage)
3) Lesions with increased pulmonary blood flow and pulmonary edema, in which diffusion barriers and intrapulmonary shunting prevent proper oxygenation (truncus arteriosus)
References
Flanagan MF, Taylor DC, "Cardiac Disease". In Avery GB, Fletcher MA, MacDonald MC, eds. Neonatology. Philadelphia: J.B. Lippincott. 1994:519.
Turley K. Intermediate results from the period of the Congenital Heart Surgeons Society Transposition Study 1985-1989. Ann Thorac Surg. 1995;60:505-510.