Chapter 13 - Disorders Of RBC Flashcards
What are the RBC?
The erythrocytes or mature RBC are the most common type of blood cell, bring 500-1000 times more numerous than other blood cells. The erythrocyte is a non i leafed, thin biconcave disk. This unique shape contributes in two ways to the oxygen transport function of the erythrocyte. The biconcaave shape provides a larger surface area for oxygen diffusion than would a spherical cell of the same volume, and the thinness of the cell membrane enables oxygen to diffuse rapidly between the exterior and the interior of the cell. Is the flexibility of the red cell membrane. They are maintained by a complex network of fibrous proteins, especially one called spectrin. It forms an attachment with another protein, called ankyrin, That resides on the inner surface of the membrane and is anchored to an integral protein that spans the membrane. This unique arrangement of proteins imparts elasticity and stability to the RBC membrane and allows it to deform easily as it moves through narrow spaces in the vascular network.
The function of the RBC facilitated by the hemoglobin molecule, is to transport oxygen to the tissues. Because oxygen is poorly soluble in plasma, about 95-98% is carried bound to hemoglobin. The molecule is composed of two pairs of structurally different alpha and beta polypeptide chains. Each of the chains consists of a globin (protein) portion and a heme unit, which surrounds an atom of iron that binds oxygen. Thus each molecule can carry four molecules of oxygen. It is a natural pigment; because of its iron content, it appears reddish when oxygen is attached and bluish cast when deoxygenated. Production of each chain is controlled by the individual structural genes with five different gene loci.
Two major types of normal hemoglobin - adult and fetal. Adult has a pair of a chains and a pair of b chains. Fetal (3-9 months) has a pair of gamma y chains substituted for the a chains. So fetal has a higher affinity for oxygen. HbF is replaced within 6 months of birth.
What is hemoglobin synthesis?
The rate at which hemoglobin is synthesized depends on the availability of iron for heme synthesis. A lack of iron results in relatively small amounts of hemoglobin in the RBC. Body iron is found in several compartment. 65% of iron is in the form of hemoglobin, with small amounts found in the myoglobin of muscle, the cytochromes, and iron containing enzymes. The reaming 15-30% is stored for later use, mainly in the liver but also in the reticuloendothelial cells of the bone marrow. Iron in the hemoglobin compartment is recycled. When RBC age and are destroyed in the spleen, the iron from their hemoglobin is released into the circulation and returned to the bone marrow for incorporation into new RBC or to the liver and other tissues for storage. Dietary sources help to maintain iron stores. Iron, principally derived from meat, is absorbed in the small intestine, especially the duodenum. When body iron stores are diminished or erythropoietin is stimulated, absorption is inc. In iron overload, excretion of iron is accelerated. Normally, some iron is sequestered in the intestinal epithelial cells and is lost in the feces as these cells slough off. The iron that is absorbed enters the circulation, where it immediately combines with a B globulin, apotransferrin to form transferrin, which is then transported in the plasma. From the plasma, iron can be deposited in tissue cells such as the liver, where it is stored as ferritin, a protein iron complex that is easily transferable back to the circulation. Serum ferritin levels can be measured in the lab to provide an index of body iron stores.
What is Red cell production?
erthropoiesis refers to the production of RBC. After birth, red cells are produced in the reed bone marrow. Until 5 years of age, almost all bones produce red cells to meet the growth needs of a child, after which bone marrow activity gradually declines. After 20 years of age, red cell production takes place mainly in the membranous bones of the vertebrae, sternum, ribs and pelvis. With this reduction the red bone marrow is replaced with fatty yellow bone marrow. The RBC are derived from precursor cells called proerythroblasts, which are formed continuously from pluripotent stem cells in the bone marrow. They move through a series of divisions, each producing a smaller cell as they continue to develop into mature RBC. Hemoglobin synthesis begins at the early erythroblast stage and continues until the cell becomes a mature erythrocyte. During its transformation from normal last to reticulocyte, RBC accumulates hemoglobin as the nucleus condenses and is finally lost. The period from stem cell to emergence of the reticulocyte in the circulation normally takes approx one week and maturation of reticulocyte to erythrocyte takes about 24-48 hours. During this process, the red cell loses its mitochondria and ribosomes, along with its ability to produce hemoglobin and engage in oxidative metabolism. Most maturing red cells enter the blood as reticulocytes.
erythropoiesis is governed for the most part by tissue oxygen needs. Any condition that causes a dec in the amount of oxygen that is transported in the blood ordinarily produces an inc in the rate of red cell production. The dec oxygen content is sensed by the kidneys, which then produce a hormone called erythropoietin. About 90% is produced by the kidneys, with the remaining 10% by the liver. It acts primarily in latter stages of erythropoiesis to stimulate the production of proerythroblasts from stem cells in the bone marrow. In kidney failure, hypoxia has little to no effect on RBC production.
What are the red cell life span and destruction?
RBC live approx, 4 months or 120 days. Even though mature red cells do not have a nucleus, mitochondria, or enroll as if reticulum, they have cytoplasmic enzymes that are capable of metabolizing glucose and forming small amounts of ATP. These enzymes also help to perserve the pliability of the cell membrane, maintain transmembrane transport of ions, keep the iron of the cells hemoglobin in the reduced ferrous form that binds oxygen, and prevent oxidation of the proteins. Even so the metabolic activity in the cell fed as the red cell ages, and the cell membrane become more and more fragile, causing it to rupture as it passes through tight places in the circulation. Many self destruct in the spleen as they squeeze through spaces between the trabeculae of the red pulp, which are only about 3 mm wide, in comparison with the 8mm width of the red cell The rate of red cell destruction 1% per day) normally is equal to the rate of red cell production
The destruction of RBC is facilitates by a group of large phagocytic macrophages found in the spleen, liver, bone marrow and lymph nodes. These cells recognize old and defective red cells and then ingest and destroy them in a series of enzymatic reactions. During these reactions, the amino acids from the globulin chains and iron from the heme units are salvaged and reused. The bulk of the heme units is converted to bilirubin, the pigment of bile, which is insoluble in plasma and attaches to plasma proteins for transport. It is removed from the blood by the liver and conjugated with glucuronide to render it water soluble so that is can be excreted in the bile. Serum levels of conjugated and unconjugated bilirubin can be measured in the lab and are reported as direct and indirect. If the rate of reed cell destruction and consequent bilirubin production exceed the liver’s ability to remove it from the blood, unconjugataed bilirubin accumulates in the blood. this results in yellow discolouration of the skin called jaundice.
When RBC destruction takes place in the circulation as in hemolytic anemia the hemoglobin remains in the plasma where it binds to the hemoglobin binding protein calle haptoglobin.
What are the lab tests?
RBc can be studied by means of a sample of blood. The RBC count measures the total number of RBC in a micro litre uL of blood. The % of reticulocytes provides an index of rate of RBC production. The hemoglobin or 100 millilitres Ml of blood measures the hemoglobin content of the blood. Major components of blood are the red cell mass and plasma volume. The hematocrit measure the red cell mass in 100 mL plasma volume.
The mean corpuscular volume MCV reflects the volume or size of the red cells. It falls in microcytic anemia and rises in macrocytic anemia.
What is anemia?
Is defined as an abnormally low number of circulating RBC or level of hemoglobin or both, resulting in diminished oxygen carrying capacity. The effects can be grouped into three categories; 1 manifestations of impaired oxygen transport and the resulting compensatory mechanisms 2. Reduction in red cell indices and hemoglobin levels, 3 signs and symptoms with the pathologic process that is causing the anemia.
It depends on severity, the rapidity of its development, underlying pathologic mechanisms, person’s age and health status. If slow the body compensates for the dec inosygen carrying capacity of the blood inc in plasma volume, cardiac output, and respiratory rate.
The redistribution of the blood from cutaneous tissue or the lack of hemoglobin causes pallor of th skin, mucous membranes, conjunctivae and nail beds. Tachycardia and palpitations may occur with inc in cardiac output. Anemia’s caused by premature destruction of red cells are associated with hyperbilirubin, jaundice. Ineffective hematopoietic are associated with inappropriately high levels of iron overload absorption from the gut , which can lead to iron overload and eventual damage to endocrine organs and the heart.
Lab tests are useful in determining the severity and cause of anemia
What is blood loss anemia?
It depends on the rate of hemorrhage and whether the bleeding loss is internal or external. With rapid blood loss, circulatory collapse may occur. With slowly developing blood loss, the amount of red cell mass lost may reach 50% without the occurrence of signs and symptoms.
The effects of acute blood loss are mainly due to loss of intravascular volume, which can lead to cardiovascular collapse and shock. The hypoxia that results from blood loss stimulates proliferation of committed erythroid stem cells in the bone marrow. It takes about 5 days for the progeny of hematopoietic stem cells to differentiate fully, Takes about 3-4 weeks to return to normal levels.
What is hemolytic anemias? What are the inherited disorders of the red cell membrane? What is sickle cell disease?
Hemolytic anemia are characterized by the premature destruction of red cells, the retention of iron and the other products of hemoglobin destruction, and a compensatory inc in erythropoiesis. Almost all types are distinguished by normal grid and normochromic red cells. Because of the shortened life span, the bone marrow usually is hyperactive, resulting in an inc number of reticulocytes in the circulating blood. The pt experiences easy fatigability, dyspnea, and other signs of impaired oxygen transport. Are commonly classified according to the red cell defect; intrinsic to the cell or due to some external factor.
Destruction of red cells can occur within the vascular compartment or within the phagocytic cells of the reticuloendothelial system. Intravascular hemolysis is less common and occurs as a result of mechanical injury caused by defective cardiac valves, complement fixation in transfusion reactions, or exogenous toxic factors. Regardless of cause, intravascular a hemolysis leads to hemoglobinemia, hemoglobinuria, and hemosiderinuria. The conversion of the heme pigment to bilirubin can result in unconjugated hyperbilirubinemia and jaundice. Massive intravascular hemolysis can lead to acute tubular necrosis. Extra vascular is the most common, takes place largely within the phagocytic cells of the spleen and liver.
Hereditary spherocytosis, in which the loss of membrane surface area relative to cytoplasmic contents causes the cell to become a tight sphere instead of a concave disk, is the most common. Which is transmitted as an autosomal dominant trait in 75% cases, is caused by disorders of the spectrin and ankyrin membrane protein that lead to a loss of membrane surface. Although the spherical cell retains its ability to transport oxygen, it is poorly deformable and susceptible to destruction as it passes through the venous sinuses of the splenic circulation. Signs typically include mild hemolytic anemia, jaundice, splenomegaly, and bilirubin gallstones. A lifethreatening aplastic crisis may occur when a sudden disruption of red cell production causes a rapid drop in the hemoglobin level. It is usually treated with a splenectomy and blood transfusions.
Sickle cell - is an inherited disorder in which abnormal hemoglobin leads to chronic hemolytic anemia, pain and organ failure. 8% of African aamericans or 30% where malaria is endemic. The abnormal structure of HbS results from a point mutation in the B chain of the hemoglobin molecule, with an abnormal substitution of a single amino acid, valine for glutamic acid. Heterozygous, 40% of hemoglobin in homozygous 80-95% hemoglobin is HbS. Variations in proportion exist, and the concentration of HbS correlates with the risk of suckling. HbS polymerizes when deoxygenated, creating a semisolid gel that makes the erythrocyte rigid, distorts its shape, and causes structural damage to the red cell membrane. It may return to its shape with oxygenation in the lungs. After repeated episodes of deoxygenation, the cell remain permanently sickles.
Two major consequences of RBC suckling - chronic hemolytic anemia and blood vessel occlusion. Overall lifespan of RBC with sickle cell is 20 days. Vessel occlusion disrupts blood flow, causing tissue ischemia and pain crisis. Factors associated with cold, stress, physical exertion, infection and illnesses that cause hypoxia, dehydration or acidosis.
Clinical course - the two. Most common basic musics pain crisis and acute chest syndrome. It results from tissue hypoxia due to vessel occlusion and can occur suddenly in almost any part of the body. Sties are abdomen, chest, bones, and joints. Many are affected simultaneously. Acute chest syndrome is atypical pneumonia resulting from pulmonary infarction. Characterized by pulmonary infiltrates, shortness of breath, fever, chest pain, and cough. Can cause chronic respiratory insufficiency and is the leading cause of death.
Diagnosis and treatment - Screening of babies heel blood test to see for sickle cell. Usually diagnosed in infancy. Prophylactic treatment with penicillin to prevent pneumococcal infection. Maintaining full immunizations, for H flu and hepatitis B. And pneumococcal vaccine. Hydroxyurea, an inhibitor of DNA synthesis has been shown to reduce pain crises and prevent the complications of sickle cell disease. It produces an inc of HbF in red cells by dec the terminal differentiation of erythroid stem cells into HbS acts as an anti imflammatory agent by inhibiting the production of WBC and is oxidized by heme groups to produce nitric oxide, a potent vasodilator and inhibitor of platelet aggregation. 40% of pt dont respond to the drug. Bone marrow or stem cell transplantation has the potential for cure but carries the risk of graft versus host disease
What is thalassemias b and a?
Are a heterogeneous group of inherited disorders caused by mutation that dec the rate of synthesis of a or b globin chains. B thalassemias are caused by deficient synthesis of the B chain and a thalassemias by deficient synthesis of the a chain. The defect is inherited as a Mendelian trait, and a person may be heterozygous or homozygous for the trait. Like sickle cell disease, the thalassemias occur with a high degree of frequency in certain populations. B is Mediterranean from southern Italy and greece, where as a is among asians. Both are more common in Africans and African Americans. Two factors - a deficiency in hemoglobin due to the dec synthesis of the affected chain, coupled with excess production of the unaffected chain. The reduced hemoglobin synthesis results in a hypo chronic, microcytic anemia, whereas the accumulation of the unaffected chain interferes with normal red cell maturation and contributes to membrane changes that lead to hemolysis and anemia.
B-thalassemias result from a point maturation in the B globin gene that directs B chain synthesis. Sequencing of the B thalassemias genes has revealed more than 100 different Mustafa ion, the majority of which consist of single base changes. The presence of one normal gene in heterozygous persons usually results in sufficient normal hemoglobin synthesis to prevent severe anemia. Homozygous have severe, transfusion dependent anemia Thats is evident at 6 months of age. Two conditions inadequate HbA formation due to reduced B globin chain synthesis, and red cell hemolysis resulting from an unbalanced rate of B globin and a globin synthesis. The excess a globin chains form insoluble aggregates that precipitate within red cells and produce severe membrane damage that causes extra vascular hemolysis. Erythroblasts in bones marrow have the same fate. No only anemia but severe suffer from coagulation abnormalities. Thrombotic events appear to be related. Severe marked anemia produced by ineffective hematopoiesis and hemolysis leads to inc erythropoietin secretion and hyperplasia in the bone marrow and sites of extramedullary hematopoiesis. Major issues with all body organs and bone. Regular blood transfusion improve growth and development and prevent most of the complications and iron chelation therapy can reduce the iron overload and extend life expectancy. Stem cell transplantation is a potential cure for low risk
A thalassemias - are caused by a gene deletion that results in defective a chain synthesis, Synthesis of the a globin chains of hemoglobin in controlled by four genes; hence a thalassemia shows great variation in severity related to the number of gene deletions. Those that have two genes have and exhibit mild hemolytic anemia. Deletion of 3-4 chains leads to unstable aggregates of a chains called hemoglobin H HbH. Most severe form occurs in infants and usually results in death in hydro or shortly after birth.
what are inhereited enzyme defects? What is acquired hemolytic anemia s?
The red cell is vulnerable to injury by endogenous and exogenous oxidants, which are normally inactivated by the glucose containing triple tide glutathione, one of the body ‘s principal means of preventing oxidative damage. Abnormalities or glutathione metabolism resulting from impaired enzyme function reduce the ability of red cells to protect against oxidative stress. The most common inherited enzyme defect that results in hemolytic anemia is a deficiency of glucose -6phsphate dehydrogenase G6PD. The gene that determines this enzyme is located on the X chromosome, and the defect is expressed only in males and homozygous females. It makes red cells more vulnerable to oxidants. The disorder features direct oxidation of hemoglobin to methemoglobin, which cant transport oxygen and denaturing of the hemoglobin molecule to form Heinz bodies, which are precipitated in the RBC. Hemolysis usually narrow vessels of the spleen, causing hemoglobinemia, hemoglobinuria, and jaundice. Can be triggered by exposure to oxidant drugs such as anti malarial drug primaquine, quinine, the shock amuses, and nitrofurantoin. Severe G6PD can be diagnosed through the use of G6PD assay and other screening blood test.
Several acquired factors exogenous to the RBC produce hemolysis by direct membrane destruction and antibody mediated lysis. Various drugs, chemicals, toxins, venoms and infections such as malaria destroy red cell membranes. Hemolysis can also be caused by mechanical factors such as prosthetic heart valves, vasculitis, and severe burns. Obstructions in the micro circulation as in DIC, thrombotic thrombocytopenia purpura TTP, and renal disease, may traumatized the red cells by producing turbulence and changing pressure gradients.
Initiated by ingested drug, the antibodies that cause hemolysis are two types; warm reacting antibodies of the immunoglobulin G IgG class, and cold reacting antibodies of the IgM type. Warm the most common form, the antibodies react with antigens on the reed cell membrane, causing destructive changes that lead to spherocytosis, with subsequent phagocytic destruction in the spleen or reticuloendothelial system. Usually have rapid onset and may be severe and life threatening. 50% are idiopathic and 50% are related to predisposing condition such as lymphoid neoplasms, autoimmune disorders lupus, and exposure to drugs penicillin and the cephalosporins.
In cold reacting agglutinin type of hemolytic anemia, which is less common IgM antibodies bind red cells and cause agglutination and activate complement. EBV and influenza, it is benign,
The diagnosis requires the use of the Coombs test to detect the presence of antibody or complement on the surface of RBC. It uses antibodies specific for human immunoglobulins or complement to detect antibodies on RBC. It is positive in cases of autoimmune hemolytic anemia, Rh disease of the newborn, transfusion reactions and drug induced hemolysis.
What area anemia’s of deficient red cell production? What’s iron deficiency anemia?
It may result from the dec production of erythrocytes by the bone marrow. Caused by a deficiency of substances that are needed for hematopoiesis, particularly iron, vitamin b12, and folic acid.
Iron deficiency anemia - is a common worldwide cause of anemia affecting person of all ages. The anemia results from dietary deficiency, loss of iron through bleeding, or inc demands. Because iron is a component of heme, a deficiency leads to dec hemoglobin synthesis and consequent impairment of oxygen delivery. Body iron is broken down and reused but a small amount is lost in stool and needs to be replaced by dietary. Needs 05-1.5 mg daily to replace the 1 mg lost.
The main reason is blood loss, it may occur from GI bleeding, in women menstruation and pregnant women per iron requirements inc. 3 - 24 months is higher need.
It is characterize by low hemoglobin and hematocrit, dec iron stores and low serum iron and ferritin levels. The red cells are dec in number and are microcytic and hypochromic. Poikilocytosis (irregular shape) and anisocytosis (irregular size).
Manifestations are related to impaired oxygen transport and lack of hemoglobin. Pallor, east fatigability, dyspnea, and tachycardia may occur. Epithelial atrophy is common and results in waxy pallor, brittle hair and nails, sometimes spoon shaped deformity of the fingernails, smooth tongue, sores in the corners of the mouth and sometimes dysphasia and dec acid secretion.
Prevention of iron deficiency is a primary concern in infants and children. Avoidance of cow’s milk, iron supplementation at 4-6 months of age in breast fed infants and use of iron fortified formulas and cereals. It’s directed toward controlling chronic blood loss, inc dietary intake of iron, and administering supplement iron.
What are megaloblastic anemia’s and the two causes? Vitamin B12 deficiency anemia? What is folic acid deficiency anemia?
Megaloblastic anemia’s are caused by impaired DNA synthesis that results in enlarged reed cells due to impaired maturation and division.
Vitamin B12 - also known as cobalamin, serves as a cofactor for tow important reactions in humans. It is essential for DNA synthesis and nuclear maturation, which in turn leads to normal red cell maturation and division. Vitamin B12 is also involved in a reaction that prevents abnormal fatty acids from being incorporated into neuronal lipids. This abnormality may predispose to myelin breakdown and produce some of the neurological complications of vitamin B12 deficiency. It is found in all foods of animal origin. It is absorbed by a unique process after release from the animal protein, it is bound to the intrinsic factor, a protein secreted by the gastric parietal cells. It protects vitamin B12 from digestion. The complex travels to the ileum, where it binds to membrane receptors on the epithelial cells, Vitamin B12 is then separated from intrinsic factor and transported across the membrane into the circulation It is bound to its carrier protein, transcobalamin II, which transports it to its storage and tissue sites.
A cause is pernicious anemia is believed to result from immunologically mediated, possible autoimmune, destruction of the gastric mucosa.. It is marked by loss of parietal cells and production of antibodies that interfere with binding of vitamin B121 to intrinsic factor. Others are gastrectomy, ideal resection, inflammation or neoplasms in the terminal ileum and malabsorption syndromes in which vitamin B12 and other b vitamins compounds are poorly absorbed.
The hallmark is megaloblastic anemia. The red cells that are produced are abnormally large because of excess cytoplasmic growth and structural proteins. The cells have immature nuclei with evidence of cellular destruction and delicate membranes that are oval rather then biconcave. These oddly shaped cells have a short life span that can be measured in weeks rather then months. The loss of red cells results in moderate to severe anemia and mild jaundice. Same pallor, easy fatigability and in severe cases dyspnea.
Diagnosis is made by finding an abnormally low serum vitamin B12 level. Lifelong treatment consisting of IM injections or high oral doses of vitamin B12 reverses anemia and prevents neurological changes.
Folic acid deficiency anemia - is also required for DNA synthesis and red cell maturation, and its deficiency produces the same type of megaloblastic red cell changes that occur . Folic acid is readily absorbed from the ingestion and found in vegetables, fruits, cereals, and meats. Common causes are malnutrition or dietary lack, especially in the elderly and alcoholics. Store 2000-5000 ug with 50 ug daily needed. Malabsorption may be due to syndromes such as celiac disease or other intestinal disorders. anti epileptic meds primo one, phenytoin, phenobarbital, and diuretic triamterene. In neoplasticism disease, tumor cells compete for folate and deficiency is common. Studies have shown an association between folate deficiency and neural tube defects.
What is aplastic anemia?
Describes a disorder of pluripotential bone marrow stem cells that results in a reduction of all three hematopoietic cell lines, RBC WBC and platelets. Onset of aplastic anemia may be insidious, or it may strike with suddenness and great severity. Can occur at any age. Presents with weakness, fatigability and pallor. Petechiae and ecchymoses often occur on the skin, and bleeding from the nose, gums, vagina or GI tract may occur because of dec platelet levels. The dec in number of neutrophiles inc susceptibility to infection.
Causes include exposure to high doses of radiation, chemicals, and toxins that suppress hematopoiesis directing or through immune mechanisms. Chemo and radiation result in bone marrow depression, causes anemia, thrombocytopenia , and neutropenia. Identified toxic agents benzene, the antibiotic chloramphenicol, and the alkylate gene agents and anti metabolites used in treatment of cancer. This may be idiosyncratic reaction because it affects only certain pt. It occurs weeks after a drug is initiated, some are severe and sometimes irreversible and fatal. Most often as a complication of viral hepatitis mononucleosis and other viral illnesses, AIDS.
Therapy in young and severely affected pt includes stem cell replacement by bone marrow or peripheral blood transplantation. Graft versus host disease rejection and infection are major risks but 75% survive. Or immunosuppressive therapy with lymphocyte immune globulin which producing remission in 50%
What is anemia of chronic disease?
Often occurs as a complication of infections, inflammation or cancer. Causes are acute or chronic infections including AIDS and osteomyelitis; cancers; autoimmune disorders as rheumatoid arthritis, lupus, and inflammatory bowel disease and chronic kidney disease. Microorganisms, tumor cells and autoimmune dysregulation lead to T cell activation and production of cytokines that suppress the erythropoietin response, inhibit erythroid precursors, and cause changes in iron homeostasis. Chronic renal failure almost always results in anemia, primarily because of erythropoietin deficiency.
What is polycythemia? What is primary and what is secondary?
Represents an abnormally high total RBC count with a hematocrit greater than 50%. Categorized as relative and absolute. In relative the hematocrit rises because of a loss of plasma volume without a corresponding inc in red cells. May occur with water deprivation, excess use of diuretics or GI losses. Is corrected by inc the vascular fluid. Absolute is a rise in hematocrit due to an inc in total red cell mass and is classified as primary or secondary.
Primary polycythemia, is a neoplasticism disease of the pluripotent cells of the bone marrow characterized by an absolute inc in total RBC mass accompanied by elevators white cell and platelet counts. Most commonly in med and may occur at any age with a median age of 62. The manifestation are variable and are related to an inc in red cell count, hemoglobin level, and hematocrit with inc blood volume and viscosity. Early findings include splenomegaly and depletion of iron stores. Viscosity rises exponentially with the hematocrit and interferes with cardiac output and blood flow. Hypertension is common and there may be complaints of headache, dizziness, inability to concentrate, and some difficulty with hearing and vision because of dec cerebral blood flow. Venous stasis gives rise to a dusky red or bluish skin color, particularly in the lips fingertips and mucous membranes. The inc concentration of blood cells, and person may experience itching and pain in fingers or toes, and hyper metabolism may induce night sweats and weight loss. Thromboembolism and hemorrhage, due to hyperviscosity and platelet and neutrophil abnormal activation, are common it can be prevented by phlebotomy to reduce the hematocrit to less than 42% in women and 45% in men.
Treatment is to reduce blood viscosity. Withdrawing blood by periodically to reduce RBC volume. Low dose aspirin may control the high platelet counts and suppression of bone marrow function with meds hydroxyurea controls the elevated WC count.
Secondary results from a physiologic inc in the level of erythropoietin, commonly as a compensatory response to hypoxia. Conditions for causing hypoxia include living at high altitudes, chronic heart and lung disease and smoking. The resultant release of erythropoietin by the kidney causes the inc formation of RBC in the bone marrow. Neoplasms that secrete erythropoietin may also cause secondary polycythemia. Kidney disease as hydronephrosis or renal cysts may obstruct blood flow, cause hypoxia and lead to an inc in erythropoietin as well.
Treatment focuses on relieving hypoxia. Continuous low flow oxygen therapy can be used to correct hypoxia in COPD. This form of treatment is thought to relieve the pulmonary hypertension and polycythemia and to delay the onset of right heart failure due to lung disease.
