Evaluation of the Cyanotic Child

Posted by e-Medical PPT Friday, July 2, 2010
Cyanosis is a bluish or purplish tinge to the skin and mucous membranes.Approximately 5 g/dL of deoxygenated hemoglobin in the capillaries generates the dark blue color which will be appreciated clinically as cyanosis. For this reason, patients who are anemic may be hypoxemic without showing any cyanosis.
A patient whose hemoglobin content is 15 g/dL (hematocrit approximately 45%) would not generate 5 g/dL of deoxygenated hemoglobin in the capillaries until his/her SaO2 level reached about 85%.
When hemoglobin content is 9 g/dL (hematocrit approximately 27%), the threshold SaO2 level for manifesting cyanosis is lowered to about 73% (PaO2 38 mm Hg). At this level of hypoxemia, the patient would certainly have other manifestations of hypoxemia (eg, respiratory symptoms, mental status changes) apart from cyanosis.
Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation in the lungs or greater oxygen extraction due to slowing down of blood circulation in the skin's blood vessels.Peripheral cyanosis is the blue tinge in fingers or extremities, due to inadequate circulation. The blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral cyanosis, but peripheral cyanosis can be observed without there being heart or lung failures.

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