Clinical Terms to the Blood

:lated anisocytosis (an-i"so-si-to'sis) Abnormal variation in the size of erythrocytes.

antihemophilic plasma (an"ti-he"mo-fil'ik plaz'mah) Normal blood plasma that has been processed to preserve an antihemophilic factor. citrated whole blood (sit'rat-ed hol blud) Normal blood to which a solution of acid citrate has been added to prevent coagulation.

dried plasma (drîd plaz'mah) Normal blood plasma that has been vacuum dried to prevent the growth of microorganisms. hemorrhagic telangiectasia (hem"o-raj'ik tel-an"je-ek-ta'ze-ah) Inherited tendency to bleed from localized lesions of the capillaries.

heparinized whole blood (hep'er-i-nîzed" hol blud) Normal blood to which a solution of heparin has been added to prevent coagulation.

macrocytosis (mak"ro-si-to'sis) Abnormally large erythrocytes.

microcytosis (mi"kro-si-to'sis) Abnormally small erythrocytes. neutrophilia (nu"tro-fil'e-ah) Increase in the number of circulating neutrophils. packed red cells Concentrated suspension of red blood cells from which the plasma has been removed. pancytopenia (pan"si-to-pe'ne-ah) Abnormal depression of all the cellular components of blood. poikilocytosis (poi"ki-lo-si-to'sis) Irregularly shaped erythrocytes.

purpura (per'pu-rah) Spontaneous bleeding into the tissues and through the mucous membranes. septicemia (sep"ti-se'me-ah) Presence of disease-causing microorganisms or their toxins in the blood. spherocytosis (sfer"o-si-to'sis) Hemolytic anemia caused by defective proteins supporting the cell membranes of red blood cells. The cells are abnormally spherical. thalassemia (thal"ah-se'me-ah) Group of hereditary hemolytic anemias resulting from very thin, fragile erythrocytes. Globin chains are missing.

Replacing Blood

The medical need to replace blood is great. Trauma victims, surgical patients, and those suffering from chronic conditions that deplete specific blood components all require blood. The World Health Organization estimates that global demand for blood exceeds 100 million units a year.

For most uses, people in need of blood receive transfusions of donated blood. The field of blood substitutes develops chemicals that have some of blood's properties for temporary use until a blood transfusion is possible.


Whole blood was used for transfusions in the past. Today, whole blood is often separated into its component parts, and only those needed are used.

A patient with anemia or an acute blood loss might receive concentrated (packed) red blood cells; a person with too few platelets might be given platelets; a person with cancer whose treatment has depleted the white blood cell count might be given a white blood cell preparation. Similarly, blood plasma might be used to replace lost blood volume or to provide clotting factors.

Before donor blood is used to obtain blood components, it is tested for particular viruses, including those that cause hepatitis B and AIDS. Then the blood components must be stored properly. For example, packed red blood cells can be stored for several years if they are frozen, but can be stored for only about a month if they are not frozen. After thawing, however, such cells must be used within about a day. Platelet preparations must be used within five days, and white blood cell concentrates must be used immediately.

Blood Substitutes

Efforts to replace blood have sought to fill in the missing fluid volume, or replicate the oxygen-carrying function. The search for blood substitutes intensified after the two world wars, when injured soldiers desperately needed transfusions, and again when the AIDS pandemic made transfusions dangerous unless blood is properly screened.

To date, there is no true blood substitute, although several pharmaceutical companies and research labs are working on it. One line of research is developing an artificial red blood cell substitute. A red blood cell substitute must meet several requirements: It must carry oxygen and give it up to tissues, be non-toxic, be storable, function until the body can take over, and not elicit an immune response.

Red blood cell substitutes are of two basic types. Perfluorocarbons are synthetic chemicals that carry dissolved oxygen. These were developed in the 1960s, and a famous photo shows a mouse apparently drowning in a beaker of the chemical—even though it is breathing while submerged. In 1990, the first red blood cell substitute was approved for use to maintain localized blood flow during certain surgical procedures. The product consists of two fluorine compounds, a mild detergent, and lipid from egg yolk.

The second type of red blood cell substitute dismantles red blood cells and isolates the oxygen-carrying hemoglobin molecules, which are then linked in various ways. The starting material is usually cow blood, or old stored human blood. A cow hemoglobin preparation saved the life of a young woman whose immune system was attacking her own blood, maintaining her circulation for several days until the illness subsided. In times past, healers used a variety of odder remedies to replace blood, including wine, ale, milk, plant resins, urine, and opium!

Typing and crossmatching blood takes precious time. Another approach to blood substitutes "cloaks" red blood cells so that they can be given to any individual, making crossmatching unnecessary. In this technique, polyethylene glycol, a chemical used as an antifreeze, forms a fuzzy coat on the cells, which masks the ABO antigens. Therefore, a recipient with an incompatible blood type does not reject these cells. Such cloaked red blood cells are being developed for use in combat, to treat chronic anemias, and for the veterinary market, which has no dog or cat blood banks. ■

Shier-Butler-Lewis: I IV. Transport I 14. Blood I I © The McGraw-Hill

Human Anatomy and Companies, 2001

Physiology, Ninth Edition

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