You are asked to see a baby who is 24 hours old. He is the third baby of the family. Mother is of African origin and has insulin-dependent diabetes. The baby was breast-feeding well until a few hours ago and has no signs of respiratory distress. The mother is worried about the baby’s colour and think he looks "blue around the lips".
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(a) What will you look for on examination?
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It is important to establish whether this is central cyanosis by looking at the lips and tongue. If there is central cyanosis it is important to perform an urgent and thorough cardiac and respiratory examination. In the absence of any respiratory distress the cause is likely to be cardiac, especially if a murmur or abnormal pulses are present.
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(b) What simple bedside investigation can help make a diagnosis of cyanotic CHD?
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Oxygen saturation should be measured in the right arm and one of the feet. If both are < 95% and there is no respiratory distress, or there is a big drop between pre- and postductal saturation then CHD is likely. The fact that the baby has been breast-feeding well makes persistent pulmonary hypertension of the newborn (PPHN) less likely. Chest radiograph may show an unusual heart shape or oligaemic lung fields but the saturation test is quicker and more useful.
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(c) What would be your immediate management if the examination and investigations suggest CHD?
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If there are convincing signs of cyanotic CHD then the child should be admitted to the NICU urgently. Oxygen therapy is unlikely to be of benefit but is usually tried until the diagnosis is clear. Prostaglandin infusion should be commenced to keep the duct open and allow blood to cross the duct. A CXR and ECG may be useful, but the diagnostic test is an echocardiogram (cardiac ultrasound).
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(d) A routine blood test shows the haemoglobin to be 22 g/dL. Is this relevant?
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Yes. Polycythaemia can lead to a proportion of the haemoglobin being desaturated (without oxygen bound to it), making cyanosis more apparent, even in the absence of hypoxia. Polycythaemia is associated with poorly controlled maternal diabetes.
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(e) What do you think the cardiac diagnosis might be?
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There is a wide variety of lesions that could be causing this picture, including pulmonary atresia, transposition of the great arteries and tricuspid atresia. TGA is 20 times more common in infants of diabetic mothers than in the background population.
For the child to have been breast-feeding well it is likely that there was an ASD or VSD in addition, which allowed a degree of mixing of oxygenated blood within the heart. As the duct closed at 24 hours the baby would have become more cyanosed and more acidotic, due to tissue hypoxia.
