Thus in a patient with severe anemia. the relative amount of reduced hemoglobin in the venous blood may be very large when considered in relation to the total amount of hemoglobin in the blood. However since the concentration of the latter is markedly reduced the absolute quantit of reduced hemoglobin may still be small and therefore patients with severe anemia and even marked arterial desaturation(稀释 )do not display cyanosisThus, in a patient with severe anemia, the relative amount of reduced hemoglobin in the venous blood may be very large when considered in relation to the total amount of hemoglobin in the blood. However, since the concentration of the latter is markedly reduced, the absolute quantity of reduced hemoglobin may still be small, and therefore patients with severe anemia and even marked arterial desaturation(稀释 )do not display cyanosis