Modern transfusion medicine recommends that it is preferable to give patients only the specific portions of blood they require. This is achieved by the use of component therapy. Therefore, whole blood is rarely used in current practice, except for exchange transfusions for neonates. A unit of whole blood contains 435 to 500 mL of blood plus a preservative-anticoagulant solution. CPDA-1 (citrate phosphate dextrose adenine) is the additive in current use. With proper collection and storage of the blood at 2° to 6°C, in the presence of this additive, whole blood has a shelf life of 35 days. The shelf life is defined as viability of at least 70 percent of the red blood cells 24 h after infusion. Whole blood is not entirely "whole" at the time of administration because during storage, beginning 24 h after collection, there is a loss of platelets and some coagulation factors. By 72 h after collection, there are virtually no viable platelets and negligible factor VIII activity in "whole" blood. Experts suggest that fewer than 10 percent of all patients requiring transfusions actually require all the components of whole blood. Whole blood has the advantage of simultaneously providing volume and oxygen-carrying capacity. This is also accomplished by the use of packed red blood cells and crystalloid solution, and this is the preferred procedure. Disadvantages to the use of whole blood transfusion are that it is rarely available in the United States; clotting factors are present in low levels; whole blood often contains elevated levels of potassium, hydrogen ion, and ammonia; the patient is exposed to a large number of antigens; and volume overload can occur before the needed components are replenished.
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