What is the function of the kidneys?

One of the main functions of the kidneys is to remove waste and excess fluids through urine. The kidneys are also responsible for regulating our body’s salt, potassium, and acid levels. In addition, they produce hormones that help regulate blood pressure, control calcium metabolism, produce vitamin D, and produce red blood cells.

What is end-stage renal disease?

Chronic kidney disease is a progressive disease that is classified into 5 stages according to the degree of kidney function. In the last stage (stage 5), the level of kidney function is below 10%. This is where the term “terminal” comes from, referring to the fact that the kidneys stop performing their vital functions. For this reason, a person with this condition needs to undergo renal replacement therapy to survive. There are three types of renal replacement therapies: hemodialysis, peritoneal dialysis, and kidney transplantation.

What is hemodialysis?

In Portugal, hemodialysis is the most common treatment modality for adults with end-stage renal disease. This is a treatment that acts as an ‘artificial kidney’, as it allows the elimination of most waste from the body’s metabolism and excess fluids. Because each individual’s nutrition is different, there are different amounts of metabolic end products that need to be removed. Healthy kidneys also regulate the composition of components such as electrolytes, water, minerals, etc. The dialysis machine takes on these regulatory tasks in addition to eliminating toxins.

How is hemodialysis performed?

During hemodialysis, blood circulates outside the patient’s body and passes through a filter (the dialyzer). After this process, the filtered blood returns to the body. All this is possible thanks to vascular access (e.g., arteriovenous fistula or central venous catheter) and a dialysis machine that allows extracorporeal blood circulation. Hemodialysis treatments are typically performed three times a week, for approximately three to four hours per session.

How does the dialyzer work?

The dialyzer has two main parts: one for the blood and one for the dialysate (the dialysis solution that allows the blood to be cleaned). Both parts are separated from each other by millions of thin membranes that the dialyzer contains. As blood passes through these fibers, excess fluids, and toxins are eliminated. These fibers, being very thin, allow blood cells and proteins to remain in the blood. Minor toxins such as urea, creatinine, potassium, phosphorus, and extra fluids are eliminated. During each dialysis treatment, only about 250 ml of blood remains outside the body.

What is a vascular access?

Vascular access is a system created surgically to transfer and return blood that is filtered during hemodialysis. For the patient, vascular access is like their lifeline, as it is a determining factor in the completion, success, and effectiveness of the treatment. The most commonly used type of vascular access is the arteriovenous fistula. There are other types of access, namely arteriovenous grafts (or prostheses) and central venous catheters.

What are the functions of the dialysis machine during treatment?

The hemodialysis machine has several different functions, all designed to make treatment as efficient and safe as possible. In addition to pumping blood from the body to the dialyzer, the hemodialysis machine controls:
Blood flow; Blood pressure; Amount of fluid removed; Other vital signs and information that help the dialysis team ensure the patient receives the best treatment possible.

Why does the dialysis machine beep?

During treatment, the dialysis machine measures the pressures inside the blood tube and dialyzer, blood flow, temperature, and the correct dialysate mixture. When treatment begins, the dialysis team sets limits to these pressures. If the machine measures any pressure outside these limits, an audible alarm will sound. This alarm allows the dialysis team to ensure the patient is safe and can take action to resolve the issue. At the end of the treatment time, the dialysis machine also emits an audible alarm.

What complications can occur during dialysis?

Muscle cramps or hypotension episodes may occur, making treatment uncomfortable. The reason why these symptoms occur varies from person to person. However, they are very commonly associated with the removal of large volumes of fluid during dialysis. If the patient feels cramps, they should notify the dialysis team so they can help and prevent the discomfort from getting worse.
Additionally, during dialysis, there is an increased risk of contracting an infection due to the nature of the treatment. The dialysis team is trained to reduce the risk of infection, but the patient also has an important role to play. Therefore, it is advisable that all patients wash their hands when entering and leaving the dialysis room. The patient should also inform the dialysis team in advance if they think they have an infection.

What happens at the end of a dialysis session?

At the end of the dialysis session, if the patient has a central venous catheter, it will be cleaned and closed until the next treatment. If the patient has a fistula or graft, the needles will be removed and the patient must press on the puncture site for approximately 15 to 20 minutes to ensure the bleeding stops.
Your blood pressure will be checked to ensure it is safe to leave the chair. This is important because some patients may experience fainting sensations shortly after standing up following treatment. Weight will be checked and recorded, just like at the beginning of each dialysis session. This assessment is important for the team to understand whether it is safe for the patient to leave the dialysis room. If, at any time, you feel unwell, inform your nursing team before leaving the dialysis unit.