Cyanosis does not occur in severe anemia because
Because reduced Hb is purple, a low aerial O2 saturation causes cyanosis. However, this is not a reliable sign of mild desaturation because its recognition depends on so many variables, such as lighting conditions and skin pigmentation. Because it is the amount of reduced Hb that is impoant, cyanosis is often marked when polycythemia is present but is difficult to detect in anemic patients.
Hypoxia stimulates erythropoietin secretion
Oxygen carrying capacity of available Hb is increased
Critical concentration of Hb required to produce cyanosis is reduced
Oxygen Dissociation Curve shifts to right
Respiratory system