Hemodialysis

Hemodialysis (or Haemodialysis) is the most common method used to treat advanced and permanent kidney failure. It is one of three renal replacement therapies, the other two being renal transplant and peritoneal dialysis. It consists of a process that uses a man-made membrane (dialyzer) to rid the body of wastes, restore the proper balance of different components of the blood, and eliminate extra fluid from the body. Although the process has been simplified throughout the years, hemodialysis is still a complicated and inconvenient therapy that requires a coordinated effort from various healthcare professionals.

Fig. 1. Illustration of a dialyzer. Source: WikiMedia Commons.

Why Hemodialysis Is Done

Healthy kidneys clean the blood by removing excess fluid, minerals, and wastes. They also make hormones that keep bonesstrong and blood healthy. When the kidneys fail either from chronic kidney disease or acute kidney injury they lose their ability to properly maintain the body’s homeostasis (internal equilibrium) by failing to:

• Rid the body of wastes, such as urea, from the blood.
• Restore the proper balance of electrolytes in the blood.
• Eliminate extra fluid from the body.

As a consequence of this failure harmful wastes build up in the body, blood pressure may rise, and the body may retain excess fluid and not make enough red blood cells. When this happens, patients need treatment to replace the function of the failed kidneys.

How Hemodialysis Works

In hemodialysis, blood is allowed to flow, a few ounces at a time, through a special filter that removes wastes and extra fluids. The clean blood is then returned to the body. Removing the harmful wastes and extra salt and fluids helps control blood pressure and keep the proper balance of chemicals like potassium and sodium in the body (Fig. 1).

Different parts of the Dialysis Unit include the following:

Dialysis machine

The dialysis machine is about the size of a dishwasher. This machine has three main jobs:

• pump blood and monitor flow for safety.
• clean wastes from the blood.
• watch blood pressure and the rate of fluid removal from the patient's body.

Dialyzer

The dialyzer is a large canister containing thousands of small fibers through which the blood is passed. Dialysis solution, the cleansing fluid, is pumped around these fibers. The fibers allow wastes and extra fluids to pass from the blood into the solution, which carries them away. Some dialysis centers may use the same dialyzer more than once for treatments. Reuse is considered safe as long as the dialyzer is cleaned before each use. The dialyzer is tested each time to make sure it’s still working, and it should never be used for more than one person. Before each session, patients should be sure that the dialyzer is labeled with his or her name and check to see that it has been cleaned, disinfected, and tested.

Dialysis solution

Dialysis solution, also known as dialysate, is the fluid in the dialyzer that helps remove wastes and extra fluid from the blood. It contains chemicals that make it act like a sponge. Doctors will prescribe a specific dialysis solution for each individual treatments. This formula can be adjusted based on how well the patient handles the treatments and on blood tests.

Needles

Fig. 2. Illustration of an arm with arterial and venous needles. Source: WikiMedia Commons.

Most dialysis centers use two needles—one to carry blood to the dialyzer and one to return the cleansed blood to your body. Some specialized needles are designed with two openings for two-way flow of blood, but these needles are less efficient and require longer sessions. Needles for high-flux or high-efficiency dialysis need to be a little larger than those used with regular dialyzers (Fig. 2).

Preparation

One of the biggest adjustments patients must make when starting hemodialysis treatments is following a strict schedule. Most patients go to a dialysis center three times a week for three to five or more hours each visit. For example, some may be on a Monday-Wednesday-Friday schedule or a Tuesday-Thursday-Saturday schedule. They may be asked to choose a morning, afternoon, or evening shift, depending on availability and capacity at the dialysis unit. In some parts of Europe, patients go to dialysis for longer hours and on a daily basis. Research has shown that slow dialysis done daily is likely better than three times a week dialysis. In USA, this can be achieved via home dialysis.

Several centers around the country teach people how to perform their own hemodialysis treatments at home. A family member or friend who will be the helper must also take the training, which usually takes at least four to six weeks. Home dialysis gives more flexibility in the dialysis schedule. With home hemodialysis, the time for each session and the number of sessions per week may vary, but the patient must maintain a regular schedule by giving him or herself dialysis treatments as often as they would receive them in a dialysis unit.

Adjusting to changes

Even in the best situations, adjusting to the effects of kidney failure and the time spent on dialysis can be difficult. Aside from the “lost time,” they may have less energy. They may need to make changes in their work or home life, giving up some activities and responsibilities. Keeping the same schedule as when their kidneys were working can be very difficult now that their kidneys have failed. Accepting this new reality can be very hard on the patient and their family. A counselor or social worker can help answer questions and help with coping.

Many patients feel depressed when starting dialysis, or after several months of treatment. This should be closely monitored and if signs of depression are observed a social worker, nurse, or doctor should be advised. This is a common problem that can often be treated effectively.

The vascular access

Fig. 3. Arm with an arteriovenous fistula. Source: WikiMedia Commons.

Fig. 4. Illustration of a looped graft. Source: WikiMedia Commons.

• Arteriovenous fistula (Fig. 3) is a surgically created connection between an artery and a vein. Arteriovenous fistulas are better than central venous catheters because they are more durable and less likely to become infected. But they are also prone to complications (thrombosis, infection, aneurysm or pseudoaneurysm). A newly created fistula may take three to six months to mature and be usable; therefore, in patients with chronic renal failure, the fistula should be created early, when GFR is between 25 and 30 mL/min. The surgical procedure anastomosis the radial, brachial, or femoral artery to an adjacent vein in an end-of-the-vein to the side-of-the-artery fashion. There is a patient advocacy group promoting the use of a fistula as the access solution in hemodialysis patients.^[1]

• Arteriovenous graft (Fig. 4) has the same principle as the fistula with the difference that an artificial vessel is used to join the artery and the vein (usually Polytetrafluoroethylene). AV grafts tend to mature faster and become usable much sooner than AV fistulas, but as they are artificial they tend to narrow and become infected more often. Another positive aspect is that they can be made to any size, thus, they can potentially be used in any part of the body (e.g. neck or thighs). The dialysis done by the graft or a fistula is better than the central venous catheter.

• A central venous catheter is a thin tube inserted into a large internal vein and is used if an arteriovenous fistula has not yet been created, or is not ready for use, or if creation of an arteriovenous fistula is impossible. The primary disadvantages of central vein catheters are a relatively narrow caliber that does not allow for blood flow high enough to achieve optimal clearance, and a high risk of catheter site infection and thrombosis (blood clots). Catheters with a subcutaneous tunnel and fabric cuff have a longer life span (50% functional at one year) and may be useful for patients in whom creation of an arteriovenous fistula is impossible.

Conditions Related to Kidney Failure and Their Treatments

Kidneys do much more than remove wastes and extra fluid. They also make hormones and balance chemicals in the body. When kidneys stop working, several problems arise, such as anemia and conditions that affect bones, nerves, and skin. Some of the more common conditions caused by kidney failure are extreme tiredness, bone and joint problems, itching, and “restless legs”. ^[2]

Anemia and erythropoietin (EPO)

Anemia is common in people with kidney disease because the kidneys produce the hormone erythropoietin, or EPO, which stimulates the bone marrow to produce red blood cells. Diseased kidneys often don’'t make enough EPO, and so the bone marrow makes fewer red blood cells. EPO is available commercially and is commonly given to patients on dialysis to reverse anemia.

Renal osteodystrophy

The term “renal” describes things related to the kidneys. Renal osteodystrophy, or bone disease of kidney failure, affects 90% of dialysis patients. It causes bones to become thin and weak or formed incorrectly and affects both children and adults. Symptoms can be seen in growing children with kidney disease even before they start dialysis. Older patients and women who have gone through menopause are at greater risk for this disease.

Itching (pruritus)

Many people treated with hemodialysis complain of itchy skin, which is often worse during or just after treatment. Itching is common even in people who don’t have kidney disease; in kidney failure, however, itching can be made worse by wastes in the bloodstream that current dialyzer membranes are unable to remove from the blood.

The problem can also be related to high levels of parathyroid hormone (PTH). Some people have found relief after having their parathyroid glands removed. The four parathyroid glands sit on the outer surface of the thyroid gland, which is located over the windpipe in the base of the neck, just above the collarbone. The parathyroid glands help control the levels of calcium and phosphorus in the blood.

But a cure for itching that works for everyone has not been found. Phosphate binders seem to help some people. These medications act like sponges to soak up, or bind, phosphorus while it is in the stomach. Others find relief after exposure to ultraviolet light. Still others improve with EPO shots. A few antihistamines (Benadryl, Atarax, Vistaril) have been found to help. Also, capsaicin cream applied to the skin may relieve itching by deadening nerve impulses. There has been some promising results with the use of gabapentin.^[3] For people who are on dialysis, taking care of dry skin is important. Applying creams with lanolin or camphor may help.

Sleep disorders

Patients on dialysis often have insomnia, and some people have a specific problem called sleep apnea syndrome, in which they have loud snoring, breaks in snoring, and apnea. Episodes of apnea are actually breaks in breathing during sleep. Over time, these sleep disturbances can lead to “day-night reversal” (insomnia at night, sleepiness during the day), headache, depression, and decreased alertness. The apnea may be related to the effects of advanced kidney failure on the control of breathing. Treatments that work with people who have sleep apnea, whether they have kidney failure or not, include losing weight, changing sleeping position, and wearing a mask that gently pumps air continuously into the nose (nasal continuous positive airway pressure, or CPAP).^[4]

Many people on dialysis have trouble sleeping at night because of aching, uncomfortable, jittery, or “restless” legs, called restless leg syndrome. There may be a strong impulse to kick or thrash the legs. Kicking may occur during sleep and disturb a bed partner throughout the night. The causes of restless legs may include nerve damage or chemical imbalances in the body.

Moderate exercise during the day may help, but exercising a few hours before bedtime can make it worse. People with restless leg syndrome should reduce or avoid caffeine, alcohol, and tobacco, and some people find relief with massages or warm baths. A class of drugs called benzodiazepines, often used to treat insomnia or anxiety, may help as well. These prescription drugs include Klonopin, Librium, Valium, and Halcion. A newer and sometimes more effective therapy is levodopa (Sinemet), a drug used to treat Parkinson’ disease.

Sleep disorders may seem unimportant, but they can impair a person's quality of life. Patients are encouraged to raise these problems with their nurse, doctor, or social worker.

Amyloidosis

Dialysis-related amyloidosis (DRA) is common in people who have been on dialysis for more than 5 years. DRA develops when proteins in the blood deposit on jointsand tendons, causing pain, stiffness, and fluid in the joints, as is the case with arthritis. Working kidneys filter out these proteins, but dialysis filters are not as effective.

Diet

Eating the right foods can help improve patients' dialysis and health. Most dialysis clinics have a dietitian to help plan meals. Following the dietitian’s advice closely will help get the most from the hemodialysis treatments. Here are a few general guidelines.

• Fluids. The dietitian will help determine how much fluid to drink each day. Extra fluid can raise blood pressure, make the heart work harder, and increase the stress of dialysis treatments. Many foods—such as soup, ice cream, and fruits—contain plenty of water. The dietitian will help with tips on controlling thirst.

• Potassium. The mineral potassium is found in many foods, especially fruitsand vegetables. Potassium affects how steadily the heart beats, so eating foods with too much of it can be very dangerous to the heart. To control blood potassium levels, it is recommended that foods like oranges, bananas, tomatoes, potatoes, and dried fruits be avoided. An easy way to remove some of the potassium from potatoes and other vegetables is by peeling and soaking them in a large container of water for several hours, then cooking them in fresh water.

• Phosphorus. The mineral phosphorus can weaken bones and make the skin itch. Control of phosphorus may be even more important than calcium itself in preventing bone disease and related complications. Foods like milk and cheese, dried beans, peas, colas, nuts, and peanut butter are high in phosphorus and should be avoided. There will probably be a need to take a phosphate binder with food to control the phosphorus in the blood between dialysis sessions.

• Salt (sodium chloride). Most canned foods and frozen dinners contain high amounts of sodium. Too much of it can increase thirst causing people to drink more fluid. The heart then has to work harder to pump the fluid through the body. Over time, this can cause high blood pressure and congestive heart failure. It is recommended that people on hemodialysis eat fresh foods that are naturally low in sodium and use only products labeled “low sodium".

• Protein. Most people on dialysis are encouraged to eat as much high-quality protein as they can. Protein helps maintain muscle and repair tissue. Protein, however, breaks down into a waste product, urea (blood urea nitrogen, or BUN), in the body. Some sources of protein, called high-quality proteins, produce less waste than others. High-quality proteins come from meat, fish, poultry, and eggs. Getting protein from these sources can reduce the amount of urea in the blood.

• Calories. Calories provide the body with energy. Some people on dialysis need to gain weight. They may need to find ways to add calories to their diet. Vegetable oils, such as olive, canola, and safflower oils, are good sources of calories and do not contribute to high cholesterol. Hard candy, sugar, honey, jam, and jelly also provide calories and energy. Patients with diabetes, however, should be very careful about eating sweets. A dietitian's guidance is especially important for people with diabetes who are on hemodialysis.

• Supplements. Vitamins and minerals may be missing from the diets of people on hemodialysis because they have to avoid so many foods. Dialysis also removes some vitamins from the body. The nephrologist may prescribe a vitamin and mineral supplement designed specifically for people with kidney failure. The prescribed supplement is taken after treatment on the hemodialysis days. Over the counter vitamins are discouraged since they may contain vitamins or minerals that are harmful to the dialyzed patient.

Clinical Trials

Several clinical research trials studying hemodialysis are ongoing. More information can be found here.

Research

Researchers are exploring whether shorter daily hemodialysis sessions, or longer sessions performed overnight while the patient sleeps, are more effective in removing wastes. Newer dialysis machines make these alternatives more practical with home dialysis. But the Federal Government has not yet established a policy to pay for more than three hemodialysis sessions a week.^[5]

• The End-Stage Renal Disease Program promotes research to reduce medical problems from bone, blood, nervous system, metabolic, gastrointestinal, cardiovascular, and endocrine abnormalities in kidney failure and to improve the effectiveness of dialysis and transplantation. The research focuses on evaluating different hemodialysis schedules and on finding the most useful information for measuring dialysis adequacy. The program also seeks to increase kidney graft and patient survival and to maximize quality of life.
• The HEMO Study, completed in 2002, tested the theory that a higher dialysis dose and/or high-flux membranes would reduce patient mortality (death) and morbidity (medical problems). Doctors at 15 medical centers recruited more than 1,800 hemodialysis patients and randomly assigned them to high or standard dialysis doses and high- or low-flux filters. The study found no increase in the health or survival of patients who had a higher dialysis dose, who dialyzed with high-flux filters, or who did both.
• The U.S. Renal Data System (USRDS) collects, analyzes, and distributes information about the use of dialysis and transplantation to treat kidney failure in the United States. The USRDS is funded directly by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) in conjunction with the Centers for Medicare & Medicaid Services. The USRDS publishes an Annual Data Report, which identifies the total population of people being treated for kidney failure; reports on incidence, prevalence, death rates, and trends over time; and develops data on the effects of various treatment approaches. The report also helps identify problems and opportunities for more focused special studies of renal research issues.
• The Hemodialysis Vascular Access Clinical Trials Consortium is conducting a series of multicenter, clinical trials of drug therapies to reduce the failure and complication rate of arteriovenous (AV) grafts and fistulas in hemodialysis. These studies are randomized and placebo controlled, which means the studies meet the highest standard for scientific accuracy. AV grafts and fistulas prepare the arteries and veins for regular dialysis.

History

An early hemodialysis, or "vividiffusion," unit. Source: National Library of Medicine, 1913.

Although experiments with dialysis are said to have occurred thousands of years ago, dialysis as we know it has its roots in the 20th century.

Kolff's hemodialysis unit, the first to be used on a human. Source: National Library of Medicine, 1944.

During the 1950s Willem Kolff, while working at Mt. Sinai Hospital in New York, gave a set of blueprints for his kidney machine to George Thorn at the Peter Bent Brigham Hospital in Boston. This led to the manufacture of the next generation of Kolff’s dialyzer, a stainless steel Kolff-Brigham kidney, which paved the way for the first kidney transplant in 1954.

Up until that time, dialysis had been seen as a solution only for patients with acute kidney problems. Those with end stage renal disease (ERSD), still had no definite solution. Dr. Belding Scribner came up with the idea of connecting patients to the dialyzer using plastic tubes, one inserted into an artery and one into a vein. After treatment, the circulatory access would be kept open by connecting the two tubes outside the body using a small U-shaped device which would shunt the blood from the tube in the artery back to the tube in the vein. This was to be known as the Scribner Shunt and although it is no longer used, it was the precursor to a definitive solution for permanent circulatory access for hemodialysis.

Dr. Scribner was also the founder of the first outpatient dialysis facility, the Seattle Artificial Kidney Center, later renamed the Northwest Kidney Centers. This created a serious issue in the arena of hemodialysis: who would have access to the machines, as the demand was far greater than the capacity of the center. Scribner deferred these decisions to an anonymous committee, which could be viewed as one of the first bioethics committees.

References

1. ↑ AV Fistula First Website: Fistula First Initiative
2. ↑ Merlino G, Piani A, Dolso P, et al. Sleep disorders in patients with end-stage renal disease undergoing dialysis therapy. Nephrol Dial Transplant. 2006 Jan;21(1):184-90. Abstract | Full Text | PDF
3. ↑ Naini AE, Harandi AA, Khanbabapour S, et al. Gabapentin: a promising drug for the treatment of uremic pruritus. Saudi J Kidney Dis Transpl. 2007 Sep;18(3):378-81. Abstract | Full Text | PDF
4. ↑ Iseki K, Tohyama K, Matsumoto T, Nakamura H. High Prevalence of chronic kidney disease among patients with sleep related breathing disorder (SRBD). Hypertens Res. 2008 Feb;31(2):249-55. Abstract | PDF
5. ↑ Suri RS,Garg AX,Chertow GM, et al.Frequent Hemodialysis Network (FHN) randomized trials: Study design. Kidney International (2007) 71, 349–359. Abstract | Full Text | PDF

External Links

American Association of Kidney Patients

American Kidney Fund

Kidney School

National Kidney Foundation, Inc.

Medicare Coverage of Kidney Dialysis and Kidney Transplant Services PDF(717 KB)

Department of Health and Human Services (DHHS): You Can Live: Your Guide for Living with Kidney Failure PDF (871 KB)