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Altered Erythrocyte Function

Terms in this set (52)

Composition of Blood
92% water and 8% solutes
6 quarts (5.5L)
Plasma
- 50-55% of blood volume
- Aqueous liquid with organic and inorganic (electrolytes)
Serum
- Plasma that has been allowed to clot to remove fibrinogen (may interfere with diagnostic tests)
Polycythemia
Increase in RBCs
Overproduction of RBCs
Blood becomes viscous --> HTN
Heart works harder to pump
Anemia
Is a reduction in the total number of erythrocytes in the circulating blood or in the quality or quantity of hemoglobin.
- Impaired erythrocyte production
- Acute or chronic blood loss
- Increased erythrocyte destruction
- Combination of the above
*Reduced O2 carrying capacity
Anisocysis
RBCs are present in various sizes.
Poikilocytosis
- RBCs are present in various shapes.
- Sickle cell anemia
Clinical Manifestations of Anemia
Reduced oxygen-carrying capacity: Hypoxia
Syncope, angina, compensatory tachycardia, and organ dysfunction
Classic anemia symptoms
- Fatigue, weakness, dyspnea, elevated heart rate, & pallor
Treatment of Anemia
Transfusions, dietary correction, and administration of supplemental vitamins or iron
Correction of the underlying condition
Macrocytic-Normochromic Anemia
Are also termed megaloblastic anemias.
RBCs are unusually large.
Deoxyribonucleic acid (DNA) synthesis is defective.
- Due to deficiencies in vitamin B12 or folate.
Ribonucleic acid (RNA) processes occur at a normal rate.
- Results in unequal growth of the nucleus and cytoplasm.
Vitamin B12 and folate
Co-enzymes for nuclear maturation and the DNA synthesis pathway
Pernicious anemia
Is the most common macrocytic anemia.
Is caused by a vitamin B12 deficiency.
Lacks intrinsic factor from the gastric parietal cells.
May be a congenital or autoimmune disorder.
- Autoantibodies against intrinsic factor
Is often unrecognizable in elderly d/t its subtlety, slow onset and presentation.
Intrinsic factor
Required for Vitamin B12 absorption
Condition that increase risk of Pernicious anemia
Past infection with Helicobacter pylori
Gastrectomy
Proton-pump inhibitors
- decrease acid production from perietal cells
Pernicious anemia
Clinical manifestations:
Weakness, fatigue
Paresthesias of the feet and fingers, difficulty walking
Loss of appetite, abdominal pains, weight loss
Sore tongue that is smooth and beefy red, secondary to atrophic glossitis
"Lemon yellow" (sallow) skin as a result of a combination of pallor and icterus (build up of bilirubin)
Neurologic symptoms from nerve demyelination
Not reversible, even with treatment
Evaluation of Pernicious Anemia
Methylmalonic acid and homocysteine levels are elevated early in the disease.
Gastric biopsy: Is a procedure that removes stomach tissue for diagnostic evaluation.
Treatment of Pernicious anemia
Parenteral or high oral doses of vitamin B12 are administered.
If left untreated, death will result.
Life-long treatment is required.
Folate (folic acid deficiency anemia)
Type of macrocytic-Normochromic anemia
Absorption of folate occurs in the upper small intestine; is not dependent on any other facilitating factors.
Is common in alcoholics and individuals with chronic malnourishment.
Is associated with neural tube defects of the fetus.
Folate
Essential vitamin for RNA and DNA synthesis.
Folate deficiency anemia
Clinical manifestations:
Severe cheilosis: Scales and fissures of the lips and corners of the mouth
Stomatitis: Mouth inflammation
Painful ulcerations of the buccal mucosa and tongue: Characteristic of burning mouth syndrome
Dysphagia (difficulty swallowing), flatulence, and watery diarrhea
Neurologic symptoms: Usually not seen
Folate deficiency anemia
Treatment
Oral dose of folate is administered daily until normal blood levels are obtained.
Life-long treatment is not necessary.
Microcytic-Hypochromic Anemias
Are characterized by RBCs that are abnormally small and contain reduced amounts of hemoglobin.
Causes:
Disorders of iron metabolism
Disorders of porphyrin and heme synthesis
Disorders of globin synthesis
Iron-deficiency anemia
Microcytic-Hypochromic anemia
Most common type of anemia worldwide
Highest risk: Older adults, women, infants, and those living in poverty
Associated with cognitive impairment in children
Evaluation:
- Serum ferritin
Iron-deficiency anemia
Causes:
Inadequate dietary intake
Excessive blood loss
Chronic parasite infestations
Metabolic or functional iron deficiency
Menorrhagia (excessive bleeding during menstruation) Use of medications that cause gastrointestinal bleeding (aspirin, nonsteroidal antiinflammatory drugs [NSAIDs])
Surgical procedures that decrease stomach acidity, intestinal transit time, and absorption (e.g., gastric bypass)
Insufficient dietary intake of iron
Eating disorders, such as pica (craving and eating nonnutritional substances such as dirt, chalk, and paper)
Iron-deficiency anemia
Clinical manifestations:
Fatigue, weakness, shortness of breath
Pale earlobes, palms and conjunctivae
Brittle, thin, coarsely ridged, and spoon-shaped (concave or koilonychia) nails
Red, sore, painful tongue
Angular stomatitis: Dryness and soreness in the corners of the mouth
Become symptomatic: When hemoglobin (Hgb) 7 to 8 g/dl
Iron-deficiency anemia
Treatment:
Identify and eliminate sources of blood loss
Iron replacement therapy: Iron dextran
Sodium ferric gluconate complex in sucrose (Ferrlecit) and iron sucrose injection (Venofer)
Duration of therapy: Usually 6 to 12 months after the bleeding has stopped but may continue for as long as 24 months
Sideroblastic Anemia
Microcytic-Hypochromic anemia
Makes up a group of disorders characterized by anemia.
Is caused by a defect in mitochondrial heme synthesis.
Altered mitochondrial metabolism causes ineffective iron uptake and results in dysfunctional hemoglobin synthesis.
Acquired vs. hereditary
Myelodysplastic syndrome
Reversible form is associated with alcoholism.
Sideroblasts
Erythroblasts that contain iron granules that have not been synthesized into hemoglobin.
Sideroblastic anemia
Ringed sideroblasts in the bone marrow are diagnostic for which type of anemia?
Sideroblastic anemia
Clinical manifestations:
Iron overload (hemochromatosis)
Enlarged spleen (splenomegaly) and liver (hepatomegaly)
Sideroblastic anemia
Evaluation:
Bone marrow examination: Diagnostic
Dimorphism: Normocytic and normochromic cells concomitantly observed with microcytic-hypochromic cells
Sideroblastic anemia
Treatment:
Identify causative agents (drugs or toxins)
Transfusion
Iron-depletion therapy
Phlebotomy
Prolonged administration of erythropoietin
Hereditary: Pyridoxine (B6) therapy; life-long maintenance therapy at a lowered dose
Congenital: Stem cell transplantation
Myelodysplastic syndrome: Recombinant human erythropoietin
Normocytic-Normochromic Anemia
Are characterized by RBCs that are relatively normal in size and hemoglobin content but insufficient in number.
No common cause, pathologic mechanisms, or morphologic characteristics exist.
Less prevalent
Aplastic anemia
Normocytic-Normochromic Anemia
Pancytopenia
- Reduction or absence of all three types of blood cells
Most anemias of this kind are autoimmune disorders; some are due to chemical exposure (benzene, arsenic, chemotherapy drugs)
Pure RBC aplasia
- Only RBCs are affected
Fanconi anemia
- Rare genetic anemia from defects in DNA repair
Aplastic anemia
Pathophysiology:
Hypocellular bone marrow that has been replaced with fat
Aplastic anemia
Clinical manifestations
Hypoxemia, pallor (occasionally with a brownish pigmentation of the skin)
Weakness along with fever and dyspnea with rapidly developing signs of hemorrhaging if platelets are affected
Aplastic anemia
Evaluation: Bone marrow biopsy
Aplastic anemia
Treatment:
Bone marrow transplantation
Peripheral blood stem cell transplantation
- May receive radiation or chemotherapy before procedure
Immunosuppression
- Antithymocyte globulin with cyclosporin
- Corticosteroidal medications
Identification of high-risk individuals
If not treated or identified, death occurs
Posthemorrhagic anemia
Normocytic-Normochromic Anemia
Acute blood loss from the vascular space
Clinical manifestations
- Depends on the severity of the blood loss
Treatment
- Intravenous administration of saline, dextran, albumin, or plasma
- Large volume losses: Fresh whole blood
Hemolytic anemia
Accelerated destruction of RBCs
Congenital vs. acquired
Intravascular vs. extravascular hemolysis
Paroxysmal nocturnal hemoglobinuria
Deficiency in CD55 and CD59: Cause complement-mediated intravascular lysis and release of hemoglobin
Anemia, hemoglobinuria, severe fatigue, abdominal pain, and thrombosis
Autoimmune hemolytic anemia
Autoantibodies against antigens normally on the surface of erythrocytes
Warm reactive antibody type
Cold agglutinin type
Cold hemolysin type (paroxysmal cold hemoglobinuria)
Based on the optimal temperature at which the antibody binds to the erythrocytes
Drug-induced hemolytic anemia
Form of immune hemolytic anemia that is usually the result of an allergic reaction against foreign antigens
Called the hapten model
Penicillin, cephalosporins (more than 90%), hydrocortisone
Hemolytic anemia
Clinical manifestations
May be asymptomatic
Jaundice (icterus)
Splenomegaly
Hemolytic anemia
Evaluation
Bone marrow: Abnormally increased numbers of erythrocyte stem cells (erythroid hyperplasia)
Hemolytic anemia
Treatment
Acquired: Removal of the cause or treatment of the underlying disorder
First line: Corticosteroids
Second line: Splenectomy and rituximab (monoclonal antibody)
Paroxysmal nocturnal hemoglobinuria: Eculizumab
Anemia of chronic disease
Mild-to-moderate anemia from decreased erythropoiesis
- Acquired immunodeficiency syndrome (AIDS), malaria, rheumatoid arthritis, lupus erythematosus, hepatitis, renal failure, and malignancies
Pathologic mechanisms:
Decreased erythrocyte lifespan
Suppressed production of erythropoietin
Ineffective bone marrow response to erythropoietin
Altered iron metabolism
Anemia of chronic disease
Competitive iron binding from increased lactoferrin and apoferritin
During inflammation, neutrophils release lactoferrin to bind iron and to reduce its availability for bacteria.
Apoferritin: Higher affinity for iron results, and available iron is affected in a similar manner.
Failure to increase erythropoiesis in response to decreased numbers of erythrocytes
Kidney damage, affecting erythropoietin (hormone for production of erythrocytes)
Clinical manifestation:
Same as iron-deficiency anemia
Evaluation:
Very high total body iron storage
Failure to respond to conventional iron replacement therapy
Treatment:
Alleviation of underlying disease
Relative polycythemia
Is a result of dehydration.
Fluid loss results in relative increases of RBC counts and hemoglobin and hematocrit values.
Resolves with fluid intake.
Primary absolute polycythemia
Abnormal regulation of the multipotent hematopoietic stem cells
Polycythemia vera
Secondary absolute polycythemia
Increase in erythropoietin as a normal response to chronic hypoxia
Inappropriate response to erythropoietin-secreting tumors
Most common type of polycythemia
Polycythemia vera
Chronic neoplastic, nonmalignant condition
Overproduction of RBCs (frequently with increased levels of WBCs [leukocytosis] and platelets [thrombocytosis])
Splenomegaly
Is an acquired mutation in Janus kinase 2 (JAK2).
Negates the self-regulatory activity of JAK2 that allows the erythropoietin receptor to be constitutively active, regardless of the level of erythropoietin.
Disease can convert into acute myeloid leukemia.
Spleen becomes enlarged, frequently with abdominal pain and discomfort.
As the disease progresses, blood cellularity and viscosity increases.
Intense, painful itching is intensified by heat or exposure to water (aquagenic pruritus)
Polycythemia vera
Treatment:
Phlebotomy: Withdrawal of 300 to 500 ml of blood at a time to reduce erythrocytosis and blood volume
Low-dose aspirin
Interferon-α
Hydroxyurea
Radioactive phosphorus
Hereditary Hemochromatosis
Common inherited, autosomal recessive disorder of iron metabolism
Characterized by increased gastrointestinal iron absorption with subsequent tissue iron deposition
Excess iron deposited in the liver, pancreas, heart, joints, and endocrine gland, causing tissue damage
Fatigue, malaise
Abdominal pain, arthralgias, and impotence
Hepatomegaly, abnormal liver enzymes, bronzed skin, diabetes, and cardiomegaly
Treatment: Phlebotomy; refrain from taking iron and vitamin C supplements and consuming raw shellfish; alcohol use in moderation
Family screening
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