Blood transfusion Blood transfusion Blood transfusion is generally the process of receiving blood or blood products into one's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but modern medical practice commonly uses only components of the blood, such as red blood cells, white blood cells, plasma, clotting factors, and platelets. Red blood cells contain hemoglobin and increase iron levels by improving the amount of oxygen found in the body. White blood cells, are not commonly used during transfusion but are related to the immune system and to fight infections.
Blood volume Blood volume Blood volume is the volume of blood (both red blood cells and plasma) in the circulatory system of any individual. A typical adult has a blood volume of approximately 5 liters, with females and males having approximately the same blood volume. Blood volume is regulated by the kidneys. Blood volume (BV) can be calculated given the hematocrit (HC; the fraction of blood that is red blood cells) and plasma volume (PV), with the hematocrit being regulated via the blood oxygen content regulator: Blood volume measurement may be used in people with congestive heart failure, chronic hypertension, renal failure