Packed red blood cells Whereas in high-income countries, most blood transfusions are given to people over 65 years of age (up to 76%). In these countries transfusion are most commonly used for supportive care in heart surgery, transplant surgery, massive trauma, and therapy for solid and blood cancers. Due to changes in surgical practices, medical use of blood is now the major use of red blood cells in high-income countries. Blood transfusion is typically recommended when hemoglobin levels reach 70 g/L (7 g/dL) in those who have stable vital signs. For those with heart disease it is recommended at 80g/L (8 g/dL). RBCs are
Red blood cell being dissolved in body fluid) was an important step in the evolution of vertebrates as it allows for less viscous blood, higher concentrations of oxygen, and better diffusion of oxygen from the blood to the tissues. The size of red blood cells varies widely among vertebrate species; red blood cell width is on average about 25% larger than capillary diameter, and it has been hypothesized that this improves the oxygen transfer from red blood cells to tissues. The red blood cells of mammals are typically shaped as biconcave disks: flattened and depressed in the center, with a dumbbell-shaped cross section,