Cyanosis

<p>The causes of cyanosis may be quickly recalled by applying the basic science of <br>physiology. Cyanosis is due to decreased oxygenation of the blood.<br> The decrease, however, cannot be mild; there must be at least 5 g of reduced hemoglobin per 100 mL of blood if cyanosis is to appear. It should be understood from the above that cyanosis will appear with less severe anoxia in polycythemia than it will in anemia. For example, a patient with 20 g of hemoglobin needs only one fourth of his or her blood unsaturated to show cyanosis, whereas a patient with 10 g of hemoglobin needs one half of his or her blood unsaturated to do the same.</p>