Dialysis

The goal for dialysis is to remove toxins and waste products from the blood, to maintain normal electrolyte levels, and to manage the amount of fluid in the body.

Definition of dialysis

Dialysis is a medical procedure that removes waste products of metabolism from the bloodstream when the kidneys are unable to perform that function.

The kidneys are important organs. They filter the blood and clear waste. Kidneys control the fluid levels in the body, blood pressure, electrolyte levels, pH (acidity levels in the body). The kidneys are also part of the system that produces red blood cells.

The kidney is made up of millions of nephrons that filter the blood. Each nephron consists of a glomerulus that filters blood, and a tubule that returns needed chemicals to the blood and gets rid of waste.

Kidney function is measured by two blood tests, creatinine and glomerular filtration rate.

• Creatinine (Cr) is a chemical waste product from muscle as it generates energy. The kidneys filter out creatinine into the urine for it to leave the body. Normal creatinine blood levels for males is 0.6-1.2 mg/dL and for females 0.5-1.0 mg/dL. The different values are due to the lower average muscle mass for females.
• Estimated glomerular filtration (eGFR) rate is calculated based on creatinine value, age, and sex. Measured GFR is rarely done because of its complexity. Normal eGFR for a person in their early 20s is about 115 mL/min/1.73m2 . The normal value falls gradually with age to 90.

Kidney failure can occur suddenly as an acute kidney injury perhaps as a consequence of trauma, major infection or poisoning, or there may be chronic kidney failure that develops gradually over time as a complication of diabetes, high blood pressure, or other chronic medical conditions affecting the kidney.

Uremia is the term that describes (urea + emia=in the blood) kidney failure. Urea and other toxins are damaging to many tissues and organs in the body, but especially the neurologic system. Symptoms may include confusion, lethargy, nausea, vomiting, and fatigue.

In acute kidney injury, dialysis is used as a temporary, urgent measure to clear waste products from the blood. The underlying reason for the kidney injury is treated and the hope is that kidney function will return to normal as the body heals.

In chronic kidney failure, the patient’s risk of declining kidney function is often identified well before the need for dialysis. Treatment is directed to slow the decline of the kidney failure to delay the use dialysis as long as possible. There are five stages of kidney failure based upon eGFR results. Stage 1 eGFR is 90 or greater. Stage 5 eGFR is less than 15. People with stage 5 kidney failure (also known as end stage kidney disease) are candidates for dialysis.

The goal for dialysis in both acute kidney injury and end stage kidney failure is the same; to remove toxins and waste products from the blood, to maintain normal electrolyte levels, and to manage the amount of fluid in the body. The difference is the expected length of time that the patient remains on dialysis. The acute kidney injury patient may be on dialysis for only a few weeks, while the chronic kidney failure patient would expect lifelong dialysis or until a kidney transplant is performed.

Hemodialysis uses a machine, called a dialyzer, to remove blood from the body, circulate it through a filter to remove waste products, and then return the clean blood to the body.

Before hemodialysis can begin, an AV fistula or graft needs to be created so there can be access to the bloodstream. A surgeon connects an artery and vein together in the arm to form a durable access point that can withstand multiple dialysis episodes a week. It will take 6-12 weeks for a fistula, or 2-4 weeks for a graft to mature or heal, before it can be used for dialysis.

Hemodialysis can be done at an outpatient center or at home. At a center, patients get hemodialysis 3 times a week, and the session on the dialyzer usually takes 3-5 hours. At home, the sessions usually happen 6 or 7 times a week but for only 2 hours at a time.

Peritoneal dialysis does not use a machine to filter waste from the blood. Instead, tubes are placed into the abdomen and the peritoneum (the lining of the abdominal cavity) is used as the filter. Fluid (dialysate) containing water is run into the abdomen and as blood naturally circulates through the peritoneum, the waste products leech from the bloodstream into the dialysate. After a few hours, the fluid is drained and with it the body’s chemical waste.

A few weeks before peritoneal dialysis begins, a surgeon will place a soft tube (catheter) through the abdominal wall into the abdomen itself.

Peritoneal dialysis is usually done daily.

• Automated peritoneal dialysis is usually done at night using a machine that empties and fills the dialysate bag 3-5 times per night.
• Continuous ambulatory peritoneal dialysis (CAPD) is usually done during the day. The patient uses gravity to empty the dialysate fluid into the abdominal cavity where it is left for 4-6 hours before being drained, again with gravity’s help. It takes about 10 minutes to empty and fill the bag. The procedure is called ambulatory because the patient can walk around and function while the fluid is in the abdomen.

Continuous renal replacement therapy is used specifically for critically ill patients in an intensive care unit. These patients who develop acute kidney injury are often unable to tolerate the amount of fluid given during a regular dialysis run over 3-5 hours. Instead, the dialysis runs continuously at a very low fluid rate. This is a temporary procedure that can only be done in an ICU.

Hemodialysis is not painful. However, during the time on the dialyzer, there are fluid shifts occurring in the body and patients may develop muscle cramps, or feelings of lightheadedness and weakness.

Peritoneal dialysis is also not painful, but with the fluid filling the abdomen, patients can feel bloated. The patient may also feel the catheter if it pushes up against the abdominal wall during fluid filling or emptying.

A patient can stay on dialysis for the duration of their life expectancy. Depending upon circumstances, some people have been on dialysis for more than 30 years.

Can kidneys start working again after dialysis?

In acute kidney injury, the hope is that as the body recovers from its injury or illness, the kidneys too will recover, and dialysis may not be needed.

In chronic kidney disease, when kidney function has finally reached stage 5 failure (end-stage-kidney-disease), it is unlikely that kidney function will return.

Can you eventually get off dialysis?

In patients with end-stage-kidney-disease, dialysis is likely lifelong. Kidney transplant offers the potential opportunity to no longer need dialysis.

Common side effects of dialysis are also some of the complaints seen in patients with kidney failure. These include the following:

• Muscle cramps,
• Weakness, lightheadedness, and fatigue
• Nausea
• Low blood pressure (hypotension)
• Bleeding
• Itching (pruritis)
• In hemodialysis, there is a risk that the AV fistula or graft could clot and close.
• With peritoneal dialysis, there is the additional risk of infection in the abdominal cavity (peritonitis) and hernia formation

The average life expectancy for a patient on dialysis is 5-10 years.

The most common causes of death are cardiovascular disease and infection.

Patients who are older than 70 when they begin dialysis have a shorter life expectancy. For those age 70-74, life expectancy on dialysis is 3.5 years. This is compared to patients who do not need dialysis whose life expectancy is 12 years.

Life expectancy depends upon the underlying medical conditions, the age of the patient, and how compliant the patient is with the medical care advised.