Anemia and your kidneys

Dr. Hugh McHugh

Although Nephrologists are specialists in kidney diseases and hypertension. They are often involved in treating anemia in patients with chronic kidney disease (CKD). Anemia is a decrease in the number of red blood cells in the body, and it is extremely common as kidney function declines. It is very gratifying for the Nephrologists to help our patients feel better by correcting this condition.

Blood is composed of three cell lines: white blood cells which fight off infections, platelets which help clot the blood, and red blood cells (RBCs) which are filled with hemoglobin, the molecule that carries oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. When the number of RBCs decreases, the amount of oxygen which can be transported to the tissues decreases as well, and people feel tired and weak. They may become pale, develop shortness of breath when they exert themselves, and feel lightheaded due to the lack of adequate oxygen to the heart and brain. Some people complain of trouble staying warm and difficulty concentrating. There are many causes of anemia, including inherited disorders of hemoglobin (such as sickle cell anemia), iron deficiency, vitamin B12 deficiency, blood loss of any kind (often in the stool), chronic inflammatory diseases (such as rheumatoid arthritis), and chronic kidney disease. The treatment of anemia depends on its cause.

The normal RBC lives about two months before it must be replaced by the blood-producing cells in the bone marrow. One of the main regulators of the number of RBCs in the blood is a hormone produced in the kidneys called erythropoietin (e-rith-ro-poí-e-tin). This hormone travels from the kidneys to the bone marrow when anemia is sensed, and it tells the bone marrow to make blood cells. If the kidneys are not functioning normally in their filtering abilities (chronic kidney disease), they often are not producing normal amounts of this hormone, which then results in anemia due to an underproduction of blood cells. When the glomerular filtration rate (roughly the percentage of kidney function) decreases to around 30%, the production of erythropoietin may decrease enough to cause anemia, although the level of function where this occurs is variable.

Before the development of manufactured erythropoietin, people with CKD had to live with the symptoms of anemia, not uncommonly needing blood transfusions when the anemia became severe enough. There are different formulations of erythropoietin, all of which are effective but with different time intervals required between injections. Hemodialysis patients generally get injections intravenously during dialysis 3 times a week. Peritoneal dialysis patients and those CKD patients not on dialysis receive subcutaneous injections (similar to an insulin injection) every one to four weeks depending on the type of product used. In order to make sure the injections are working and to make sure the rate of correction of anemia is not too rapid, the patient will have to go to the laboratory every 2-4 weeks for a blood test. The normal blood hemoglobin level is 14-18 g/dl for men, 12-16 for women; we aim for a level of 11-12 with erythropoietin injections. Medicare and insurances often look at the hematocrit, another measure of anemia that is roughly three times the hemoglobin level (normal 42-54%). The goal hematocrit is 33-36%. If the level of hemoglobin or hematocrit goes too high, the doctor may hold further doses of the medication until the levels drift down again over the next few weeks.

Since these medicines are quite expensive, it is important to know that Medicare and insurances pay for erythropoietin injections in CKD patients when we can document a significant anemia (generally a hemoglobin less than 11 or a hematocrit less than 33) along with decreased kidney function. If Medicare is your primary insurance, you will have to come to the doctor’s office for the injection; other health insurances may want you to give the injection to yourself at home.

From personal experience, we find that patients feel better after having their anemia improved with injections. In addition, medical studies have shown that treated dialysis patients have improved quality of life parameters, including increased energy and improved sleep. Other studies have shown improved blood flow to the brain and improved cognitive function, while another trial in men showed improvement in sexual dysfunction. When used to correct anemia in CKD patients not yet on dialysis (pre-dialysis patients), studies have shown improved energy, a decrease in heart left ventricular mass, and an improved survival of patients after they started dialysis.

Given the advantages of this well tolerated therapy, we would encourage patients with CKD to ask their doctor whether they have anemia. If anemia is present, improving the red blood count may make a significant difference in how they feel.



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