This is common in babies and young children. It is usually confined to the area around the mouth ("muzzle area") and the hands and feet. Whilst it may occur when exposed to a cold environment (e.g. after a long time in the bath) there is often no obvious reason and it may occur on warm and sunny days. It usually lasts for a few minutes and the child is asymptomatic and unaware of any problem. The technical term for this colour change is acrocyanosis. It is probably caused by local variation in blood flow through the skin - the longer the transit time the greater the extraction of oxygen from the blood and the more intense the colour change. It is of no consequence and usually goes away as the child gets older.
This is present when the tongue itself is noted to be blue. This occurs when there is more than 5g of reduced haemoglobin per 100 ml blood. It is therefore more easily seen in those with polycythaemia and masked when anaemia is present. In general the oxygen saturation needs to be below 85% for cyanosis to be detectable to the eye. Central cyanosis may be due to cardiac, respiratory, neurological or haematological disorders. The clinical situation usually allows them to be distinguished however sometimes it can be difficult and co-existing disease may be present.
When cyanosis has been present for more than 6 months then clubbing almost invariable occurs.
The history together with the examination, chest X-ray and capillary gas usually allows the diagnosis to be made. A cardiac diagnosis is more likely if the respiratory rate is normal or only slightly increased, the pulmonary vascular markings are abnormal on the X-ray or the cardiac size or shape is abnormal. The pCO2 is usually normal or low. Murmurs are often uncommon even in significant cardiac disease. The hyperoxia test is still useful. Measure the oxygen saturation in as low an oxygen concentration as possible and then again after ten minutes of an oxygen concentration of 100%. In respiratory disease there will usually be a significant rise in the oxygen saturation (15-20% or more) and an adequate level reached (85% or more).
In infants the major cause of central cyanosis is respiratory as most cyanotic cardiac disease has already presented in the neonatal period. The exceptions are those disorders with a normal or high pulmonary blood flow e.g. Tetralogy of Fallot, Pulmonary atresia with MAPCAs, unobstructed TAPVC and single ventricle physiology.
Adolescence & Adult Period
There are a substantial number of severely cyanosed patients in this age group who have either had definitive palliative treatment for cyanotic cardiac disease (e.g. systemic-pulmonary shunts for pulmonary atresia) or have developed Eisenmenger syndrome (e.g. unoperated AV septal defects, Trisomy 21). Their chronic hypoxaemia leads to an increase in erythropoietin production and hence an isolated increase in red cell mass. For many patients therefore the increase in red cell mass is appropriate, enhances oxygen delivery to tissues and is asymptomatic.
These usually occur in tetralogy of Fallot. The mechanisms are uncertain but probably involve either an increased pulmonary vascular resistance or decreased systemic vascular resistance. This leads to an increased R-L shunt across the VSD and hence exacerbates the hypoxia, hypercarbia and acidosis further increasing the pulmonary vascular resistance and creating a downward spiralling process.A spell usually occurs for no apparent reason, often early in the morning although some may be precipitated by induction of anaesthesia, following a bath or when upset). The infant becomes pallid or cyanosed, is irritable with prolonged cry. If examined the intensity of the murmur may have decreased as less blood is ejected across the pulmonary valve.
Spells may be brief (minute or two) and self correct or may progress with the infant developing paroxysms of rapid, deep respirations, becoming grey, floppy and unresponsive. Without appropriate treatment a severe spell may be life threatening. The treatment is to
administer 100% O2
place infant in knee-chest position or compress both femoral arteries directly
give intramuscular morphine sulphate
give intravenous propranolol
If the spell continues full cardio-respiratory support may be required. Note Spells may occur even after a surgical shunt and may occur in other conditions, e.g. Pulmonary atresia with MAPCAs, Eisenmenger syndrome.
The increase in red cell mass increases blood viscosity and in some patients causes symptoms. These include headaches, light-headedness, slow mentation, visual disturbance, paraesthesia, tinnitus, fatigue, myalgia and muscle weakness. Iron deficiency is commonly associated as the additional erythropoiesis necessitates an increased iron requirement. Iron deficient red blood cells are microcytic but despite being small are less deformable than normal cells and so also increase the viscosity. Those symptomatic patients with an haematocrit < 65% are thus probably iron deficient.
Polycythaemic patients also have bleeding tendencies. Usually this is mild – bleeding gums after teeth brushing, epistaxis but may be life threatening in severe pulmonary haemorrhage (this was the fate of the 32 year old man reported by Victor Eisenmenger in 1897). The bleeding tendency appears to be a combination of reduced platelet counts (usually they have an inverse relationship to the haematocrit) and a reduction in von Willibrand factor. It may well be exacerbated by the injudicious use of antiplatelet and anticoagulant medication and self administration of NSAIDs.
The high red cell production (and hence destruction) increase uric acid production which the kidneys are unable to readily excrete as their function is depressed in polycythaemia. Gout is not uncommon in this group of patients and may be exacerbated by diuretic treatment.
Patients vary in their tolerance of a high haematocrit and may be asymptomatic even at levels > 70%. Recent evidence also suggests that neither the haematocrit nor iron stores are linked to the risk of cerebral arterial thrombo-embolism. Thrombosis can certainly occur but appears to be related to abnormal vascular beds.
The rationale for treatment is therefore purely for symptomatic relief. Phlebotomy, when indicated, should remove 250-500 ml of blood with replacement of the same volume with normal saline. The beneficial effects usually are manifest within 24 hours but only last for as long as the erythropoietin production takes to increase the red cell mass again. Frequent venesection will cause iron deficiency anaemia unless supplementation is given. Pain relief and allopurinol is usually effective in gout.