A Review of Anemia in Hemodialysis Patients

Introduction

The intention of this paper is to explore causal factors and consequences of anemia as it relates to renal failure; to examine agents used to combat anemia for those who suffer from renal failure and undergo hemodialysis and how administration of the essential trace element iron is utilized in current treatments. The structure of this paper will consist of five segments beginning with a brief review of anemia, followed by a short discussion of iron deficiency anemia. Then the relationship between renal failure, anemia and iron deficiency will be explored. Finally, current measures used in combating anemia in hemodialysis patients such as recombinant human erythropoietin will be examined.

Anemia

Anemia is a pathological deficiency in the number of red blood cells (erythrocytes), usually measured in unit volume concentration of hemoglobin. Hemoglobin is an iron-containing protein that enables the transport of oxygen from the lungs to all of the body's muscles and organs. Oxygen provides the body with the energy needed to perform normal activities. The structure of hemoglobin consists of a globin portion which is made up of polypeptide chains (two б-chains and two в-chains) and four heme groups. Each heme molecule contains one iron ion ligand in its center which allows for the binding of oxygen (Gropper, p. 427, 2005). Anemia occurs when the number of red blood cells or the hemoglobin within the cells fall below normal ranges (normal hemoglobin for men is 14 -18 g/dl and normal hemoglobin for women is 12-16g/dl [Understanding Anemia, 2005]). When hemoglobin levels fall below ll-12 g/dl, the transport of oxygen becomes compromised, hence leaving the body without the energy needed to function properly. If left untreated, the consequences of anemia lead to substantial morbidity and mortality.

There are several types of anemia which include the following:

Anemia - B12 deficiency

Anemia - folate deficiency

Anemia - iron deficiency

Anemia due to chronic disease

Hemolytic anemia

Hemolytic anemia - G-6-PD deficiency

Idiopathic aplastic anemia

Idiopathic autoimmune hemolytic anemia

Immune hemolytic anemia

Immune hemolytic anemia - drug-induced

Megaloblastic anemia

Pernicious anemia

Secondary aplastic anemia

Sickle cell anemia

As the above list indicates, there is a wide range of potential causes of anemia such as blood loss, nutritional deficits, various diseases, reactions to medications and problems with bone marrow (Brose, M., 2004). For the purpose of this paper we shall examine the occurrence of anemia as a result of renal failure and the consequences of iron deficiency.

Iron deficiency, Anemia and Renal Failure

Iron deficiency is a worldwide common nutritional problem causing iron-deficiency anemia in more than 500 million people. Iron deficiency is associated with low birth weight,..."defects in cognitive and psychomotor development in children and impaired work capacity for adults" (Gupta, et al, 1999). Since iron is a central component of hemoglobin, deficiencies in iron inhibit hemoglobin synthesis. The amount of iron present in the body varies with sex, age, and body size. Normal adults have between 2 - 5 g of iron present in the body; 4 g for average adult males; 2 g for average adult females. A majority of iron is found in hemoglobin (65%) with roughly 25% in storage as ferritin and hemosiderin primarily stored in bone marrow. The main iron transport protein is transferrin. Each molecule of transferrin can bind two iron (Ferric) atoms.

Anemia is a significant obstacle for hemodialysis patients with chronic renal failure and understanding the underlying cause of anemia and iron deficiency is imperative for appropriate treatment.

The kidneys play a pivotal role in the production of red blood cells. Erythropoiesis (red cell production) takes place in bone marrow. For this process to begin the kidney cells must release the hormone erythropoietin (EPO), a glycoprotein that is a growth factor for red blood cell stem cells. The release occurs when oxygen content in blood is low. The hormone travels to bone marrow and stimulates red blood cell precursors to divide and terminally differentiate into reticulocytes (immature red blood cells) which then develop into mature cells over a period of 24 - to - 48 hours (Rolfes, Pinna & Whitney, 2005). As renal failure progresses, adequate EPO is not produced by kidney cells and red blood cell production is compromised.

The most commonly used therapy to combat anemia for hemodialysis patients is the use of a recombinant human erythropoietin (rHuEPO) (Berns, Elzein, Lynn, Fishbane, Meisels & DeOreo, 2003), epoetin alfa and while this therapy improves physiologic quality of life, raises hemotocrit and hemoglobin concentrations, 25 - 37% of patients still fail to achieve normal hemoglobin levels (Folkert,