2. the fluid portion of the
blood, in which the formed elements (blood
cells) are suspended. Plasma is to be distinguished from
serum, which is plasma from which the
fibrinogen has been separated in the process of clotting. Called also
blood plasma. adj.,
adj plasmat´ic, plas´mic.
Of the total volume of blood, 55 per cent is made up of plasma. It is a clear, straw-colored liquid, 92 per cent water, in which are contained plasma
proteins, inorganic salts, nutrients, gases, waste materials from the cells, and various hormones, secretions, and enzymes. These substances are transported to or from the tissues of the body by the plasma.
Plasma obtained from blood donors is given to persons suffering from loss of blood or from shock to help maintain adequate blood pressure. Since plasma can be dried and stored in bottles, it can be transported almost anywhere, ready for immediate use after addition of the appropriate fluid. Plasma can be given to anyone, regardless of blood type. (See also
transfusion.)
Plasma volume is sometimes measured in order to calculate the total
blood volume. The most common method for determining plasma volume is by injection of a dye (T-1824, called Evans blue) into the circulating blood and, after the dye has been dispersed throughout the body, using the dilution of the dye to calculate the total blood volume.
plasma exchange the removal of plasma from withdrawn blood (
plasmapheresis) and retransfusion of the formed elements and type-specific
fresh frozen plasma into the donor; done for removal of circulating antibodies or abnormal plasma components.