Hemodialysis, Hemofiltration And Hemodiafiltration

Table of contents:

Hemodialysis, Hemofiltration And Hemodiafiltration
Hemodialysis, Hemofiltration And Hemodiafiltration

Video: Hemodialysis, Hemofiltration And Hemodiafiltration

Отличия серверных жестких дисков от десктопных
Video: Modes of Therapy - CRRT Explained! 2023, January

Hemodialysis, Hemofiltration & Hemodiafiltration

Hemodialysis and hemodiafiltration are the “classic” forms of dialysis and, in addition to kidney transplantation, the most frequently used renal replacement therapy. The blood is freed of waste products outside the body in a special dialysis machine and then flows back into the circulation in a purified form. In addition, it is also possible to add substances during the treatment. These usually take place in special dialysis centers.


  • Continue reading
  • more on the subject
  • Advice, downloads & tools
  • How is hemodialysis performed?
  • What is a dialysis shunt?
  • What do hemofiltration and hemodiafiltration mean?
  • What does hemodialysis mean in everyday life?
  • What complications can arise?

Other forms of renal replacement therapy are hemofiltration, which is related to hemodialysis, and peritoneal dialysis. Which treatment is used must be decided individually for each patient.

How is hemodialysis performed?

Hemodialysis and hemodiafiltration are the most common forms of dialysis. The blood is filtered using a dialysis machine that works like an artificial kidney. The patient's blood circulation is connected to this device via a hose system: the blood is fed into it, cleaned with the help of a special filter (dialyzer) and then returned to the circulation.

The filtering of the blood through the dialyzer works in part on a principle similar to that of the kidney. The blood flows through numerous capillaries that are surrounded by a special dialysis fluid (dialysate). The walls of these capillaries are constructed like semipermeable (partially permeable) filters, that is, they are permeable for some substances (e.g. for water, electrolytes and other small-molecule substances), but not for others (e.g. for blood cells or other larger substances that enter the blood should be preserved).

A material exchange or transport takes place between the blood and the dialysis fluid. There are two driving forces responsible for this:

  • On the one hand, there is a difference in the concentration of certain substances between the two liquids. Substances that are to be filtered out of the blood are not contained in the dialysis fluid or are contained in smaller quantities; these substances “migrate” out of the blood according to the principle of diffusion. Conversely, the concentration of substances that are to be added to the blood (eg nutrients) is higher in the dialysis fluid; these substances therefore “migrate” into the blood.
  • The second driving force is a negative pressure in the dialysate circuit, which means that substances can also be removed from the blood with the liquid (substance transport by convection).

Waste products are filtered out of the blood, the concentration of water and electrolytes is balanced and other substances (such as sodium, potassium, glucose or bicarbonate) are added to the blood as required so that the blood sugar and the acid-base balance are not unbalanced bring to. The composition of the dialysis fluid can be adjusted individually. The purified blood then flows back into the patient's circulation via a tube. During each session, the entire blood volume is pumped through the dialysis machine about 15 times.

The hemodialysis treatments usually take place three times a week (chronic intermittent hemodialysis) in special dialysis centers and each last around three to five hours. Hemodialysis can also take place at home under certain conditions. The patient must be trained in detail in special training courses.

What is a dialysis shunt?

Access to the blood vessels must be established for every dialysis treatment. A normal vein would not tolerate such frequent piercing; it would become inflamed and hardened. In addition, the blood flow in the veins is too low to ensure adequate blood flow through the dialysis machine (approximately 300 ml of blood are removed and cleaned per minute). Although blood pressure is much higher in the arteries, they are harder to reach because they are deeper under the skin. In addition, they cannot be punctured several times a week, as this would lead to the vessels becoming blocked.

For these reasons, the patients receive a so-called dialysis shunt before a well-planned start of dialysis treatment. This means that a connection between a vein and an artery is created as part of a small surgical procedure. This causes the blood to flow through this vein at a higher pressure and cause it to expand. It gets thicker and thicker over time and is then clearly visible and palpable under the skin. The expansion also thickens the wall of the vein. Overall, the shunt ensures that the vein is easy to find and that it can withstand frequent punctures over a long period of time. Initially, the puncture can be a bit painful (like taking a blood sample), but over time the puncture site becomes less sensitive to pain.

In most cases, the shunt is placed on the forearm. The procedure can usually be carried out under local anesthesia. It should take place six to eight weeks before the first dialysis treatment.

A central venous catheter (CVC) can alternatively be inserted for patients who do not want a shunt system or for whom certain factors speak against this procedure. Even in acute dialysis, a CVC is usually chosen as the access. It is less suitable for long-term dialysis treatments, partly because of the higher risk of infection.

What do hemofiltration and hemodiafiltration mean?

The hemofiltration represents a special form of hemodialysis. Also there's blood is passed in a special dialysis machine and filtered there. However, there is no dialysate and thus the transport of substances by diffusion, but that by convection is maximized. The blood water (serum) is pressed through a relatively large-pored filter (filtration), drawing waste products and other components of the blood with it. Since larger amounts of fluid have to be removed here to enable detoxification, they are returned to the body in the form of electrolyte solutions.

With hemofiltration, a relatively large amount of water can be removed from the body quickly and in a targeted manner and the blood volume can be controlled. Larger substances that only diffuse slowly are removed more effectively than with hemodialysis, while low-molecular-weight urinary substances are less effective.

Hemofiltration usually has to be applied continuously for 24 hours. It is only used in inpatient hospitals or in intensive care units. Areas of application include acute kidney failure after shock.

The hemodiafiltration is a combination of hemodialysis and hemofiltration. It makes use of the advantages of both methods; this allows both smaller and larger urinary molecules to be removed more effectively. The cleaning and detoxification effect is significantly higher than with the respective individual processes. Hemodiafiltration is a common treatment for chronic kidney failure. As with hemodialysis, the sessions take place three times a week in specialized centers.

What does hemodialysis mean in everyday life?

Which type of dialysis is most suitable is decided individually. In addition to the medical aspects, the changes in daily life that the treatments bring with them play a major role for those affected.

The hemodialysis treatments usually take place three times a week in special dialysis centers and each take around three to five hours. Depending on where you live, you may need to travel a long way - this is very time-consuming for those affected. In some cases, hemodialysis can be done at home. The prerequisite for this is that the patient has the appropriate support (e.g. from the partner) and that the necessary hygienic and technical requirements can be met.

In addition to the three treatment days, hemodialysis four days a week are treatment-free, which many consider an advantage over peritoneal dialysis. Overall, patients have to take on relatively little personal responsibility during hemodialysis and are subject to more frequent professional controls.

What complications can arise?

In general, any form of renal replacement therapy can lead to disturbances in the acid-base balance or to fluid and electrolyte shifts if these are not appropriately balanced. Regular medical checks are therefore necessary in every case. In addition to the general state of health, certain laboratory values ​​(e.g. creatinine, potassium, sodium, phosphorus) as well as blood pressure and body weight (including as a measure of the body's water content) must be checked regularly. Depending on the findings, the composition and the amount of dialysis fluid can be adjusted accordingly.

Possible complications of hemodialysis are:

  • Increased bleeding tendency: With hemodialysis there is a risk that the blood will clot in the shunt or inside the dialysis machine. Therefore, a blood-thinning drug is added during the treatments (anticoagulation); The standard is heparin. Depending on the underlying disease, kidney patients may also need permanent blood thinning. The risk of bleeding, especially in the gastrointestinal tract, after accidents, etc. is increased in these cases. For people who are particularly at risk of bleeding, the blood thinning can alternatively only take place in the hose system, without this becoming effective in the body.
  • Circulatory problems associated with dizziness, tiredness or muscle cramps; The cause is often the relatively rapid withdrawal of fluid from the circulation and the associated drop in blood pressure.
  • Cardiac arrhythmias (especially rapid heartbeat, palpitations); The cause is often a rapid change in the potassium balance. If the potassium level is in the normal range immediately before treatment, there is a risk that hypokalaemia (a decrease in the potassium level in the blood) will develop in the course of treatment. The concentration of electrolytes in the blood should therefore be checked at regular intervals before dialysis.
  • Chest pain or heart trouble. To compensate for the drainage and maintain blood pressure, the heart needs to work harder during treatments. For patients with pre-existing heart disease (e.g. coronary artery disease, heart failure) this can mean a worsening of their situation.
  • Hemolysis, which is the destruction of red blood cells. The cause can be kinks in the hose system, which damage the erythrocytes. The consequences are, among other things, EKG changes, abdominal pain, nausea, vomiting. However, thanks to modern dialysis technology, this complication is rarely observed.
  • Intolerance reactions. This leads to incompatibilities to components or substances within the dialyzer, which manifest themselves in the form of nausea and shortness of breath, chest and stomach pain, among other things.
  • Complications in the area of ​​the dialysis shunt, such as bleeding or infections at the puncture site as well as narrowing or blockage of the dialysis shunt (e.g. due to thrombus formation or vascular changes).

Popular by topic