Red Blood Cell Disorders

Function of the Red Blood
Transportation of oxygen to the tissues
Hemoglobin binds some carbon dioxide and carries it from the tissues to the lungs
The hemoglobin molecule is composed of two pairs of structurally different polypeptide chains
Each of the four polypeptide chains consists of a globin (protein) portion and heme unit, which surrounds an atom of iron that binds oxygen
The Function of the Red Blood (cont.)
Each molecule of hemoglobin can carry four molecules of oxygen.
The production of each type of globin chain is controlled by individual structural genes with five different gene loci
Mutations can occur anywhere in these five loci
Erythropoiesis
Red cells are produced in the red bone marrow after birth
Until age 5 years, almost all bones produce red cells to meet growth needs; after 5 years, bone marrow activity gradually declines
After 20 years, red cell production takes place mainly in the membranous bones of the vertebrae, sternum, ribs, and pelvis
With this reduction in activity, the red bone marrow is replaced with fatty yellow bone marrow

Red Blood Cell Destruction
The red blood cell has a life span of approximately 120 days
It is broken down in the spleen
The degradation products (iron and amino acids) are recycled
The heme molecule is converted to bilirubin and transported to the liver
It is removed and rendered water soluble for elimination in the bile
Laboratory Tests for Red Blood Cells
Red blood cell count (RBC)
Measures the total number of red blood cells in 1 mm3 of blood.
Percentage of reticulocytes (normally approximately 1%)
Provides an index of the rate of red cell production.
Laboratory Tests for Red Blood Cells (cont.)
Hemoglobin (grams per 100 mL of blood)
Measures the hemoglobin content of the blood.
Hematocrit
Measures the volume of red cell mass in 100 mL of plasma volume

Anemia
Definition
An abnormally low number of circulating red blood cells or level of hemoglobin, or both
Results in diminished oxygen-carrying capacity
Causes
Excessive loss or destruction of red blood cells
Deficient red blood cell production because of a lack of nutritional elements or bone marrow failure
Manifestations of Anemia
Impaired oxygen transport with the resulting compensatory mechanisms
Reduction in red cell indices and hemoglobin levels
Signs and symptoms associated with the pathologic process that is causing the anemia
Hemolytic Anemias
Inherited disorders of the red cell membrane
Hemoglobinopathies
Sickle cell anemia
Thalassemias
Inherited enzyme defects
Acquired hemolytic anemias
Anemias of Deficient Red Cell Production
Iron deficiency anemia
Megaloblastic anemias
Cobalamin deficiency anemia
Folic acid deficiency anemia
Aphasic anemic
Chronic disease anemia
Red Blood Cell Components Used in Transfusion Therapy
Whole blood
Red blood cells
Leukocyte-reduced blood cells
Washed red blood cells
Frozen red blood cells
Transfusion Therapy
Provides the means for replacement of red blood cells and other blood components
Four major ABO blood types are determined by the presence of absence of two red cell antigens: A and B
The presence of D antigen determines the Rh-positive type
The absence of the D antigen determines the Rh-negative type

Signs and Symptoms of Transfusion Reactions
Sensation of heat along the vein where the blood is being infused
Flushing of the face
Urticaria, headache, pain in the lumbar area
Chills, fever, constricting pain in the chest
Cramping pain in the abdomen
Nausea, vomiting
Tachycardia, hypotension, and dyspnea
Polycythemia
Definition
A condition in which the red blood cell mass is increased
Types
Relative polycythemia: results from a loss of vascular fluid and is corrected by replacing the fluid
Polycythemia (cont.)
Primary polycythemia: a proliferative disease of the bone marrow with an absolute increase in total red blood cell mass accompanied by elevated white cell and platelet counts
Secondary polycythemia: results from increased erythropoietin levels caused by hypoxic conditions such as chronic heart and lung disease

Diagnosis of Anemia in the Elderly
Complete physical examination
Complete blood count
Peripheral blood smear and a reticulocyte count and index
Studies to rule out comorbid conditions such as malignancy, gastrointestinal conditions that cause bleeding, and pernicious anemia