How Dialysis Machines Work
Dialysis is used in patients with rapidly developing loss of kidney function, called acute kidney injury, or slowly worsening kidney function, called Stage 5 chronic kidney disease, also known as end-stage renal disease and end-stage kidney disease). You often see that term abbreviated as ESRD.
Dialysis is also used as a temporary measure in either acute kidney injury or in patients who are awaiting a kidney transplant. The first successful dialysis in a human was performed in 1943 by Dr. Willem Johan Kolff, a Dutch physician. The early trials of dialysis were not very successful. However, Dr. Kolff continued to improve his equipment, and by the early 1950’s dialysis was successful in treating patients with acute kidney injury. However, dialysis could not be used to treat patients with chronic (permanent) kidney failure until 1962, when the first permanent vascular access was invented by Dr. Belding Scribner. Up to that time, dialysis required repeated surgical procedures to connect a patient’s blood vessels to the dialysis machine. Dr. Scribner’s access allowed patients to be connected and disconnected from dialysis easily, and repeatedly. This paved the way to using dialysis, on a long-term basis, for patients with chronic, irreversible kidney failure (End-Stage Renal Disease). Dr. Scribner and his colleagues also developed a portable dialysis machine, which allowed patients to receive treatments at home. In the early days of dialysis (the late 1960’s), approximately 40% of patients received hemodialysis at home. The other 60% were typically receiving the treatment in the
hospital, often in the critical care area. Another nephrologist, Dr. Constantine (Gus) Hampers, pioneered the development of outpatient dialysis clinics. Until the end of the 1960’s, dialysis was often performed in the critical care area of hospitals. Dr. Hampers and his colleagues developed policies and procedures that allowed dialysis to be performed safely in an outpatient clinic. This was the birth of the modern-day dialysis clinic. Many improvements have been made to the dialysis equipment over the past 50 years. The equipment now has many features that make dialysis a very safe and effective procedure that can be performed in a clinic, or at home.
How does hemodialysis work?
Hemodialysis is a treatment that replaces the work of your own kidneys to clear wastes and extra fluid from your blood. This is done using a special filter called a dialyzer. Your blood travels through plastic tubing to the dialyzer, where it is cleaned and then returned to your body.
To get your blood into the dialyzer, the doctor needs to make an access, or entrance, into your blood vessels. This is done with minor surgery, usually to your arm. At the beginning of each treatment, two needles are placed into your access. These needles are connected to the plastic tubing that carries your blood to the dialyzer.
Only a small amount of blood remains outside of your body at any given time. The dialysis machine pumps your blood through the dialysis system and controls the treatment time, temperature, fluid removal and pressure.
This basic process is the same for home hemodialysis, except that you and a care partner are trained to do your treatment at home.
Hemodialysis Vascular Access
Hemodialysis, which requires the rapid circulation of blood from the patient through the dialysis filter, requires access to the patient’s circulation. Blood is circulated through the dialysis filter at a rate of 250 ml/minute to 500 ml/minute. (500 ml/minute is the equivalent of approximately 1 pint per minute!). A patient’s peripheral vein does not have enough blood flow to support hemodialysis. A vein usually gives up blood at a rate of less than 20 ml/minute, in contrast to the minimum dialysis requirement of 250 ml/minute. The hemodialysis vascular access is created to accommodate the blood flow requirements of hemodialysis.
There are three general forms of hemodialysis vascular access. They are (i) AV Fistula; (ii) AV Graft; (iii) Dialysis Catheter. AV (Arterio-Venous) Vascular Access: The preferred form of vascular in most patients is called an ‘AV Fistula’. Another form is called an ‘AV Graft’. ‘AV’ is the abbreviation for Arterio-Venous’. With the AV Fistula, or the AV Graft, a patient’s artery is connected to a vein, usually in the arm, but sometimes in the thigh. This connection creates a vessel (under the skin) that has very rapid blood flow, which can supply blood to the dialysis machine at the rapid rate which is required to perform dialysis.
Dialysis Catheter Vascular Access:
A Dialysis Catheter is also known as a Central Line, Central Venous Catheter (CVC), Tunneled Catheter, Vascath, or Permcath. This is a plastic tube that has 2 openings (known as ‘lumens’); one is an opening (arterial port) for blood to flow out of the body and another opening (venous port) is for blood to return into the body after it flows through the dialysis machine
A hemodialysis catheter can be inserted into veins in the groin, chest, or neck; however, these catheters are usually inserted in the chest or neck. There are two general forms of a dialysis catheter; one form is temporary, the other is more permanent. The temporary catheter is usually called a Vascath or Central Line. The more permanent form is usually called a Permcath or Tunneled Catheter. The Permcath (Tunneled) Catheter is surgically inserted and is less prone to infection or inadvertent removal than the Vascath or Central Line.
Advantages of an AV Access: An AV access is preferred because the AV Access is less likely to become infected than a Dialysis Catheter. Usually the AV Access has higher blood flow than a Dialysis Catheter, which improves the efficiency of the dialysis. Dialysis Catheters tend to lose their efficiency over time and often require replacement. Patients often begin hemodialysis with a Dialysis Catheter because it takes weeks to months for an AV Graft or AV Fistula to mature after it is surgically created. Ideally, the AV Graft or AV Fistula is created before the patient needs to start hemodialysis. Unfortunately, many patients don’t realize they will be on dialysis before it is needed, and that does not leave time for the placement and maturation of an AV access. The Dialysis Catheter can be placed and used immediately, which allows immediate initiation of dialysis for patients who need urgently require dialysis, but don’t have an AV access. There are some patients in whom a Dialysis Catheter may become the permanent form of hemodialysis vascular access because they have other medical problems that preclude the creation of an AV access. The choice of access requires collaboration between the nephrologist, the surgeon, and the patient, and is individualized to each patient.
A lot of improvements are planned for the care of patients with chronic kidney disease (CKD) and End-Stage Kidney Disease (ESKD/ESRD). Regulatory Support:
In July 2019, President Trump issued the “Executive Order on Advancing American Kidney Health”. In the Executive Order, the President states:“It is the policy of the United States to:
- (a) prevent kidney failure whenever possible through better diagnosis, treatment, and incentives for preventive care;
- (b) increase patient choice through affordable alternative treatments for ESRD by encouraging higher value care, educating patients on treatment alternatives, and encouraging the development of artificial kidneys; and
- (c) increase access to kidney transplants by modernizing the organ recovery and transplantation systems and updating outmoded and counterproductive regulations.”
The Executive Order instructed the Secretary of the Department of Health and Human Services (which runs the Medicare and Medicaid programs) to: “….Select a payment model to evaluate the effects of creating payment incentives for greater use of home dialysis and kidney transplants for Medicare beneficiaries on dialysis.”
“….produce a strategy for encouraging innovation in new therapies through the Kidney Innovation Accelerator (KidneyX), a public-private partnership between the Department and the American Society of Nephrology.”
“…streamline and expedite the process of kidney (transplant) matching and delivery to reduce the discard rate.” and to
“….propose a regulation to remove financial barriers to living organ donation.”
Various rules, regulations, and pilot programs have been, and continue to be developed by CMS (Medicare and Medicaid), to implement the President’s Executive Order.
One thrust of the Executive Order is the promotion of home dialysis. Most nephrologists believe that home dialysis is more desirable than in-center dialysis. Despite this belief, only 10% of the dialysis patients in the United States receive dialysis at home. Home modalities include home hemodialysis by a family member and/or the patient, staff-assisted home hemodialysis, and peritoneal dialysis. Several technology options have emerged over the past 10 years, and more are coming. The changes include hemodialysis machines that are less complicated to operate, improved peritoneal dialysis cyclers, including one that can report the nightly treatment results over the Internet, home monitoring devices like electronic scales and blood pressure cuffs that can report daily results to the home dialysis team, and devices designed to reduce the rate of infections related to the use of peritoneal and hemodialysis catheters.
Modality Education: Many patients are not made aware that home dialysis is available. This can be overcome with ‘Modality Education’. Modality education is the process of explaining the various options available for treating ESKD. Ideally, a patient will receive this education before starting dialysis, but it is never too late to inform and remind patients of the various modalities, even after starting dialysis.