Peripheral cyanosis and central cyanosis

As we think about the differential between peripheral cyanosis and central cyanosis, again a distinguishing feature with regards to the mucous membranes is that in peripheral cyanosis the mucous membranes are pink. In contrast to cyanotic mucous membranes in central cyanosis as with congenital heart disease or pulmonary disease. The pulse oximetry can be helpful in terms of peripheral cyanosis. The pulse oximetry can be very normal, whereas in central cyanosis the saturation is abnormal. But I must warn you – because this happened to me in my clinic just last week – the examination rooms were particularly cold that day and I had two children, both of whom had had Fontan’s, and Fontan’s often have some peripheral vasomotor instability. Pulse oximetry on those children were alarming as far as their digits were concerned; 70 and 80. But they were very very cold. We put the pulse oximetry on the earlobe and they were 94 to 96. So we have to be careful with this choice of differential of central versus peripheral cyanosis. Again, usually if it is peripheral cyanosis the extremities are cool, in contrast to central cyanosis where the extremities are often very warm and well perfused. If we want to try to distinguish further, central cyanosis – pulmonary versus cardiac – then some observations can be helpful. With crying, often the babies will pink up. If it’s pulmonary, as they take deeper inspirations, overload lungs fill up. Whereas with cardiac cyanosis, often with crying that cyanosis increases. The presence of respiratory distress can sometimes be helpful in distinguishing a baby who looks comfortable but is cyanotic, is having congenital heart disease, versus those babies who are cyanotic based on respiratory disease that show some other evidence of distress.

The electrocardiogram may be helpful in that it may be abnormal in cardiac, but that is not an absolute, as we will point out as we go along with case discussion. The chest x-ray can be helpful if it’s normal. If it’s abnormal, as far as cardiomegaly or abnormal contour, then that may gear your thinking more toward cardiac cyanosis. If we look at blood gases, for example the PCO2 is often increased abnormally in pulmonary, whereas with cyanosis-related congenital heart disease the PCO2 is often normal. The hyperoxic test – giving the baby 100% oxygen or close thereto – usually with even significant pulmonary disease you get a positive response with increase in oxygen saturation and PO2. Whereas you may have little or no response to hyperoxic tests in the babies with cyanotic congenital heart disease.

As we look at an x-ray, as another point of trying to help us focus on cyanotic congenital heart disease and the specifics of congenital heart disease, we look for patterns of pulmonary flow in addition to abnormal heart contour or size. If the pulmonary flow is increased then it is likely we are dealing with one of these three congenital heart diseases; cyanotic congenital heart disease, transposition, total anomalous or truncus arteriosus. If the pulmonary vascular flow is decreased then we are more likely dealing with these anomalies; tetralogy, pulmonary atresia, tricuspid atresia, or some other forms of complex congenital heart disease with either pulmonary atresia or pulmonary stenosis.

If we focus on cyanotic congenital heart diseases and try to resolve the case presentation, if we think of the five T’s then we have included the majority of cyanotic congenital heart diseases that may be represented here in this patient; tetralogy of Fallot being the most common, representing about 10% of congenital heart disease. Transposition of great arteries representing about 5% of all congenital heart disease, tricuspid atresia representing only about 1-2% as is true also with truncus or a total anomalous pulmonary venous return. So if you guess tetralogy then you are probably going to be on the right track for the majority of patients.

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