Anemia in Kidney Disease & EPO too
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Published: September 23, 2009
Anemia for the normal population is defined as having less than the normal quantity of red blood cells within the blood. Each individual red cell contains within it the substance hemoglobin. This substance carries oxygen within the cell and releases it in organs where it is needed most. Oxygen is derived from the lung and the process of taking up oxygen into the red cell from the lung is known as oxygenation. Patients with chronic kidney disease are usually anemic for various reasons some of which are specific to kidney disease.
Anemia in CKD
photo credit: Andrew Mason
Patients with anemia have symptoms such as weakness and general lethargy, poor appetite, decreased capacity to exercise and usually describe themselves as generally unwell. The hormone responsible for the production of red blood cells is erythropoietin or epo. It is produced by the kidney, it then travels to the bone marrow where it stimulates the cells there to change into red blood cells and enter the circulation.
Patients with kidney disease may have anemia because the damaged kidney is unable to produce epo. The presence of toxins which accumulate in kidney disease also have a negative impact on the bone marrow to produce cells. Because of the depressed appetite present in patients with kidney disease there may be inadequate intake of the nutrients required to form the building blocks for the production of red blood cells. Patients with kidney disease are also deficient in iron due to slow leaks of iron from the gut due to the build up of toxins within the blood. When on dialysis there is blood lost in the dialysis tubing that further compounds this iron deficiency. Because of decreased levels of vitamin D there maybe elevated levels of another hormone known as PTH which can lead to damage of the bone marrow and decreased ability to produce red blood cells.
Treatment of anemia in kidney disease therefore relies on first determining the cause of the anemia. In addition to the usual causes detailed above, patients may also have anemia due to the preexisting diseases that cause anemia of which there are many. The evaluation to determine the cause never assumes that the anemia is only due to kidney disease.
If it is established that anemia is entirely due to kidney disease then treatment may commence by replacing the nutrients required for generation of red blood cells, iron and vitamins usually. Provision of adequate dialysis where necessary and the administration injectable of synthetic epo.
Epo is administered in such a manner as to maintain your blood count in the region of 11 to 12 grams of hemoglobin (Hb). Any higher and there is a risk of adverse events such as stroke or heart attack any lower and the benefits in terms of well being may be less than ideal.
Recently studies have suggested that there may be benefits of higher doses of epo. The authors of one study found that targeting a higher Hb around 12 g/dl was more beneficial than targeting conventional Hb in terms of reduction of the size of the heart and quality of life. Enlargement of the heart is a very serious complication of hypertension and anemia which can lead to early death in patients on dialysis. The fact that epo at higher doses may reduce the occurrence of this is exciting. In fact epo has recently been found to have a possible regulatory role in the function of the heart where studies have shown that administration of epo has direct effects on the muscle cells of the heart improving their function this study suggests that erythropoietin may have a direct positive effect on the heart and brain unrelated to correction of the anemia by reducing cell death and by increasing new blood vessel growth, both of which could prevent tissue damage. This could have profound therapeutic implications not only in heart failure but in the future treatment of myocardial infarction, coronary heart disease, strokes, and renal failure. These effects are independent of the effect of epo on the bone marrow.
However the current guidelines are based on very well done studies which have demonstrated increased mortality in patients with hemoglobin levels of greater than 12 g/dl. Other authors however are of the opinion that the increased mortality may not be due to the actual level of the hemoglobin but the dose of epo and iron required to get you there. These same authors are usually of the opinion that slowly increasing the levels of Hb over a longer period of time may be beneficial.
Erythropoietin currently is the best therapy available for anemia of chronic kidney disease. The exact dose and rate of increase in hemoglobin is likely to be revealed in upcoming studies.
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About Roger: Dr. Roger Smith is a nephrologist currently employed to the government of Jamaica. He is the Nephrologist in charge of Spanish Town Dialysis Unit. His interests are lupus nephritis and other glomerulopathies. He was previously a lecturer in Nephrology at the University of the West Indies in the Department of Internal Medicine and Coordinator of the Urogenital Module before moving into private and government practice. |
