ANEMIAS IN RENAL DISEASE
The degree of anemia in patients with end-stage renal disease varies greatly, but in general patients do not become significantly anemic until the serum creatinine level exceeds 3 mg/100 mL. The symp-toms of anemia are often the most disturbing of the patient’s symp-toms. The hematocrit usually falls to between 20% and 30%, although in rare cases it may fall to less than 15%. The RBCs appear normal on the peripheral smear.
This anemia is caused by both a mild shortening of RBC life span and a deficiency of erythropoietin (necessary for erythropoiesis). As renal function decreases, erythropoietin, which is pro-duced by the kidney, also decreases. Because erythropoietin is also produced outside the kidney, some erythropoiesis does continue, even in patients whose kidneys have been removed. However, the amount is small and the degree of erythropoiesis is inadequate.
Patients undergoing long-term hemodialysis lose blood into the dialyzer and therefore may become iron deficient. Folic acid deficiency develops because this vitamin passes into the dialysate. Therefore, patients who receive hemodialysis and who are ane-mic should be evaluated for iron and folate deficiency and treated appropriately.
The availability of recombinant erythropoietin (epoetin alfa [Epogen, Procrit]) has dramatically altered the management of ane-mia in end-stage renal disease by decreasing the need for RBC transfusion, with its associated risks. Erythropoietin, in combina-tion with oral iron supplements, can raise and maintain hematocrit levels to between 33% and 38%. This treatment has been success-ful with dialysis patients. Many patients report decreased fatigue, increased energy, increased feelings of well-being, improved exer-cise tolerance, better tolerance of dialysis treatments, and improved quality of life. Hypertension is the most serious side effect in this patient population when the hematocrit rapidly increases to a high level. Therefore, the hematocrit should be checked frequently when a patient with renal disease begins erythropoietin therapy. The dose of erythropoietin (epoetin alfa) should be titrated to the hematocrit. In some patients, the elevated hematocrit and associ-ated hypertension may necessitate antihypertensive therapy.