By Dr. Robert Lynn
The kidneys are involved in so many different bodily functions that it is impossible for dialysis to replace everything a healthy kidney can do. By staying on the kidney diet (also known as a renal or dialysis diet) plus following fluid restrictions can help the dialysis treatments do a good job in removing wastes and keeping the body's water weight normal.
Besides going for dialysis treatments and following the dialysis diet, there are medicines that help maintain a higher quality of health for a longer possible time. This article talks about some of the medical problems that may occur when the kidneys no longer function and which medicines your doctor may prescribe.
Patients who actively participate in their medical care — including understanding their medicines — usually come out ahead when it comes to feeling their best.
Anemia occurs when a person has a low red blood cell count. Anemia causes:
Most people with chronic kidney disease (CKD), and nearly all patients with end stage renal disease (ESRD) who are on dialysis, have anemia, since the kidneys make and secrete the hormone erythropoietin. This hormone is responsible for keeping a normal red blood cell count.
Since 1989 erythropoietin has been available by injection. Most patients with anemia due to chronic kidney disease who are not yet on dialysis will receive it as an injection — directly under the skin. Most patients with renal failure on hemodialysis will get the hormone during each treatment by intravenous injection into the return dialysis tubing. Most peritoneal dialysis (PD) patients will get erythropoietin by injection directly under the skin.
Normally, red blood cells make up about 36-44% of the blood; the remainder is a combination of white blood cells, platelets and the liquid called plasma in which these cells live. Before erythropoietin was available, most dialysis patients had a red blood cell count of only 20-26%. Frequently, blood transfusions were needed to keep the count even at that level. Now with proper management patients with chronic kidney disease on dialysis have normal red blood cell counts. The erythropoietin hormone given to patients goes under the names of: Procrit®, Epogen®, ARANESP® or epoietin alpha.
In order for erythropoietin to work well, iron needs to be present to make red blood cells. Without iron fewer red blood cells are made, and are smaller in size and not able to carry as much oxygen. Small amounts of red blood cells — with their iron — are lost during a hemodialysis session. If the iron is not replaced, eventually dialysis patients lack enough iron and erythropoietin and do not function as well.
Because of this, most dialysis patients need to receive iron.
Oral iron can be used, but frequently is not effective, because many people find it causes stomach pains and constipation. Sometimes the iron losses are too great to be replaced by oral iron.
Many dialysis units now give small amounts of intravenous iron during hemodialysis.
Regular blood tests will tell your doctor if you need iron therapy. There are three different types of intravenous iron and they go under the names of InFeD®, Ferrlecit® and Venofer®. Because InFeD® can cause severe (although very rare) allergic reactions, most dialysis units today will use either Ferrlecit® or Venofer® for iron replacement.
With careful iron management and the use of erythropoietin, over 90% of patients can enjoy energy levels that come from having a normal red blood cell count.
People with chronic kidney disease and those on dialysis can experience loss of bone minerals, including calcium and phosphorus. The calcium and phosphorus can also mix together, get hard and build up (forming calcifications) in the small blood vessels of the feet, intestines and heart. This condition can lead to amputations, abdominal pain, gangrene of the intestines and heart failure. The cause of bone disease and calcifications come about due to the mix of dietary calcium, phosphorus, vitamin D and a hormone called PTH (parathyroid hormone). PTH is secreted by four small glands located on the surface of the thyroid gland in the neck.
Active vitamin D controls the balance of calcium, phosphorus and PTH. With renal failure the vitamin D the body gets from sunlight and food is inactive. When PTH levels rise, there is inflammation in the bones, plus calcium and phosphorus are lost out of the bones. Because of kidney failure, the kidneys can no longer get rid of the extra phosphorus that’s in the blood. Dialysis removes only a little bit of phosphorus. High phosphorus levels plus calcium become solid in small blood vessels. Preventing or reversing this process can be done through diet and medicines such as phosphorus binders.
Even when patients limit foods that are high in phosphorus, they would still have a high phosphorus level if they didn’t take their phosphorus binders. The binders prevent the body from absorbing the phosphorus from the foods eaten.
Calcium-containing binders are effective in preventing phosphorus absorption by combining with the phosphorus in the intestinal tract. Calcium acetate, also called PhosLo®, is one commonly used phosphorus binder. There are many others, usually containing calcium carbonate. Even Tums®, which is a form of calcium carbonate, can be effective. Because most patients will require 3 to 6 pills/capsules with every meal, calcium absorption from these medicines can be significant enough to cause concern.
Some of the calcium from these binders is absorbed into the bloodstream and might deposit in small blood vessels, causing organ damage. Two other medicines, Renagel® (sevelamer) and Renvela (sevelamer carbonate) have been used as a phosphate binders. These medicines mix with phosphorus in the intestinal tract, but do not contain calcium.
All three medicines are effective in lowering phosphorus levels, but they need to be taken with every meal and with snacks. An even newer medicine, Fosrenol® (lanthanum carbonate) has been approved for use. Like the other medicines, it binds phosphorus in the intestinal tract and needs to be taken with every meal. Unlike the other two medicines it is designed to be a chewable tablet.
Although limiting foods with phosphorus from the diet is very important, active vitamin D is necessary in maintaining normal PTH levels and in bone health. High PTH levels cause inflammation of bones, muscles and tendons, loss of bone calcium and phosphorus and may be the reason for severe itching in some dialysis patients.
The oral form of active vitamin D may be effective in preventing high PTH levels in patients with chronic kidney disease. Currently, the three most available oral medicines are Rocaltrol® (calcitriol) and Hectorol® (doxercalciferol) and Zemplar (paricalcitol). These oral medicines work better for those with chronic kidney disease who are not yet on dialysis than they do for dialysis patients. Therefore, these medicines are usually given to dialysis patients intravenously during hemodialysis.
Two commonly used intravenous forms of active vitamin D administered at dialysis are Zemplar® (paricalcitol) and Hectorol® (doxercalciferol) . In many ways these are similar to the others, but may decrease the tendency to cause high blood calcium levels when compared to calcitriol (called Calcijex® when given intravenously).
Another class of medicines called "calcimemetics" has been developed. One called Sensipar® (cinacalcet) is given orally and is highly effective in lowering PTH levels. This medicine, available since April 2004, is just coming into general use in dialysis patients and its exact role is still being defined.
The dialysis procedure removes large amounts of water-soluble vitamins, such as vitamin C, B-complex vitamins and folic acid. While a good diet can usually keep up with these losses, many dialysis patients don’t always have an appetite. Most nephrologists feel that the use of a B-complex vitamin along with folic acid is a good protection for when patients don’t have a good appetite. Some vitamins include Nephro-Vite®, Nephrocaps® and Nephroplex®. These are commonly used, since they have been designed to replace losses specific to dialysis therapy.
Many dialysis patients have itching and dry skin. While it is important to learn why and correct the cause, the itching can frequently be treated with topical hydrating agents or topical cortisone along with oral antihistamines, such as Benadryl® (diphenhydramine), Atarax® or Vistaril® (hydroxyzine) or Zyrtec® (cetirizine).
Some patients are prone to leg cramps not only while on dialysis, but during the nighttime, as well. This can be due to the rapid fluid and electrolyte shifts in and out of muscle cells from the hemodialysis treatment. Vitamin E has been said to help many patients as a preventative measure for cramps when taken either before dialysis or at bedtime.
There are many other medications in use, which are not for dialysis itself but are related to the most common causes of kidney disease.
Patients with diabetes mellitus represent 40% of patients on dialysis. Their diabetes needs to be carefully controlled, not only with diet, but with either pills or insulin shots designed to maintain normal blood glucose.
Patients with high blood pressure (hypertension) need to be treated by establishing at an appropriate dry weight, following a low sodium diet, limiting the amount of fluid consumed and the use of high blood pressure medicines.
Since heart disease is common in dialysis patients many studies are now looking at medicines that can decrease the rate of heart disease. High homocysteine levels are commonly found in patients with heart disease and are also found in patients on dialysis. High doses of folic acid can lower homocysteine levels and high dose folic acid therapy is being evaluated as a possible preventative treatment in dialysis patients.
Likewise, the HMG co-a reductase inhibitors, more commonly known as "statins" (Lipitor®, Zocor®, Pravachol®, and others), are being studied even for patients on dialysis who don’t have high cholesterol, because these drugs seem to lower the rate of heart disease.
Patients with chronic kidney disease as well as those on dialysis need to be involved in all areas of their care. For chronic kidney disease patients who have diabetes and/or high blood pressure, they need to keep those conditions under control, watch their diet and take medicines as directed by their doctors. For patients on dialysis, an understanding of dialysis and following the dialysis diet are not enough. They must be an active member of their health care team by making sure that they understand and take the medicines they need to improve their longevity and quality of life.
Dr. Robert Lynn is a nephrologist in Bronx, New York. He received his BA and MMS degrees from Rutgers then went onto Columbia for his MD. His postgraduate training was done at Presbyterian Hospital in New York City for Internal Medicine followed by his specialty in Nephrology at Yale University School of Medicine in New Haven, Connecticut.
Dr. Lynn is certified with the American Board of Internal Medicine, the American Board of Nephrology and has a New York State License. His academic appointments include: Clinical Assistant Professor of Medicine at the University of Connecticut (1981-1983), and at the Albert Einstein College of Medicine: Assistant Professor of Medicine (1983-1989), Associate Professor of Medicine (1989-1994) and Clinical Associate Professor of Medicine (1994-Present).
Dr. Lynn has had a longstanding interest in dialysis—both hemodialysis and peritoneal dialysis—and has done research in the areas of anemia and bone disease in dialysis patients. He has been invited to lecture, and has written on chronic kidney disease for many publications.
Dr. Lynn has received many awards and was cited in New York Magazine as “Best Doctors in New York” for Nephrology in 1996 and 1998 as well as “Best Doctors in the Northeast” from 1996 to 2004. He is currently president of ESRD Network #2 (New York State).
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