dialysis

General

Dialysis is one apparatus Method for treating certain diseases or symptoms in which the Kidneys of the body cannot do its work adequately or not at all or the patient no longer has a kidney.

In principle, in all the variants used, the patient's entire blood is passed through a kind of filter, freed from pollutants and excess water and then returned to the body in a purified state - hence the popular synonym for dialysis: blood washing. In most cases it is therefore a renal replacement therapy due to terminal kidney failure. The first dialysis on sick people, which corresponds to today's principle, was carried out in Gießen in 1924. The technology became accessible to a wider audience from around 1945 and has been subject to constant development since then with a growing number of areas of application. Nowadays, dialysis is the mainstay in the treatment of kidney replacement therapy, so that in 2010 there were around 70,000 patients in Germany permanently requiring dialysis, and the trend is rising.

Functions of the kidney

The kidney, of which every person usually has two, is one of the most important organs in the body, without which a person would not be able to live. Not only does it regulate the body's water balance through urine excretion. In addition, it filters pollutants from the blood that the body cannot break down and plays a decisive role in maintaining the electrolyte composition of the blood, i.e. the dissolved salts and ions. In addition, hormones such as Epo (Erythropoietin), which is important for blood production and should be known to most from cycling, and the PH value regulated. The pH is a measure of the ratio of chemical acids and Bases in the blood, which must be kept constant within narrow limits. The kidneys also play a decisive role in regulating blood pressure. This shows the importance of this organ and thus dialysis as an important therapeutic option.

Areas of application

When using dialytic therapy, one must between acute Complaints and chronic Distinguish diseases. In the area of ​​acute events, dialysis is suitable for the rapid restoration of vital functions. The main areas of application here are that acute, sudden kidney failure or severe, non-medicated, and acute overhydration poisoning. However, dialysis is of greatest relevance as the most important instrument of the Renal replacement therapy. This is always used when the kidneys themselves can no longer perform the tasks assigned to them or can no longer perform them adequately. On the one hand, this happens when the kidneys are no longer present, e.g. as part of a Tumor therapywhere both kidneys had to be removed. Second, however, the vast majority of dialysis patients have one chronic renal failurei.e. kidneys working too poorly. In both cases, the above tasks will be carried out by Dialysis machine accepted. In rare cases, dialysis is also given to one Liver disease for use.

functionality

Generally becomes a extracorporeal, dialysis from outside the body from a intracorporealto distinguish dialysis running inside the body. Most of the cases are extracorporeal treatments. Here the patient is connected to the external dialysis machine, which then does the blood washing.

There are several technical principles for washing the blood. What all methods have in common is that access to the patient's blood must first be created. This is done via catheters (a type of thin tube) (acute) or dialysis shunts (chronic). The catheter frequently used in acute dialysis is the Shaldon catheter, which provides access to large peripheral veins on the neck or in the groin and thus enables blood to flow to and from the dialysis machine. If a patient is dependent on dialysis for a longer period of time or for a long time, it makes sense to create a permanent access in the form of an arterio-venous shunt. Usually located on the forearm, one of the two forearm arteries is connected directly to the neighboring vein in a small surgical operation so that arterial blood flows in this vein (so-called Cimino fistula). This type of shunt can be recognized by the fact that the vein in the affected area has a large widening and is so easy to puncture. You can feel the blood flow in the shunt with your bare hand, and sometimes you can hear a hissing noise.

Two accesses are then made to this shunt: one leads blood to the dialysis machine, the other takes the cleaned blood and feeds it back into the body. The steps to clean the blood then take place in the connected dialysis machine. In addition, the modern dialysis machine has several filters, e.g. prevent gas bubbles from forming in the blood, which can lead to complications. It is also possible to administer medication during dialysis via additional injection points. The heart of the device, which is usually about the size of a small chest of drawers, is always a semipermeable membrane. This means that a membrane is built in that has many microscopic pores and is therefore semi-permeable: water, ions and smaller particles such as the unwanted pollutants can pass through the membrane. The pores are too small for larger particles dissolved in the blood and they remain in the blood. Above all, this includes blood cells (red, white blood cells and platelets) or vital proteins that you don't want to filter out.

Two mechanisms directly on the membrane are important, which are used to purify the blood and thus determine the possible variants for carrying out dialysis: hemodialysis and hemofiltration (Greek: haima = blood). Hemodialysis is based on the principle of osmosis. It describes the behavior of particles dissolved in water, in this case in blood, to distribute themselves evenly on a semipermeable membrane along differences in concentration on both sides of the membrane. To make use of this effect in practice, you need a specific solution for successful dialysis, the dialysate, which is located on one side of the membrane.

The patient's blood is drawn from the other side. The composition of the dialysate is precisely tailored to the needs of the patient and thus enables an easily controllable exchange of substances between blood and dialysate along the membrane.

An example: If there is too much potassium in the patient's blood, a dialysate with a low potassium concentration is selected so that the excess potassium ions migrate through the membrane out of the blood until a desired value is reached. In this way it is possible to regulate all substances that can pass through the membrane up or down. Excess water, which leads to edema, can also be withdrawn from the body in this way. In contrast to this, hemofiltration is basically the same structure inside the device, but here a difference in concentration is not responsible for the exchange of substances. Instead, a pump creates a slight negative pressure on the semipermeable membrane, so that water and dissolved substances are continuously withdrawn.

Both methods offer the option of optimizing the dialysis result by adding the desired substances or fluids from the dialysis machine to the blood. A combination of both principles is also used in practice and is known as hemodiafiltration. Up to this point, the typical, far more frequently used principle of extracorporeal dialysis has been described. When intracorporeal dialysis is rarely used, a tube is implanted under the patient's abdominal wall and flushed with solutions. Here, however, the body's own peritoneum, which lies against the inside of the abdominal wall, serves as a membrane. One speaks of peritoneal dialysis.

execution

From when a patient has inadequate kidney function and thus requires dialysis is based on the clinical picture of the patient along with certain Laboratory values certainly. This is a value well related to kidney function Creatinine. Nevertheless, increasing this value is not enough to definitely justify the start of dialysis. As a more important and meaningful kidney value, the glomerular filtration rate (GFR) used. It is a measure of how well the kidneys can filter the blood and thus clean it. The normal GFR value for young adults is 100-120 ml / min.

This value naturally steadily decreases with age. However, from approx. 10-15 ml / min the chronic kidney weakness is so severe that permanent dialysis can no longer be avoided. In addition, acute incidents in the context of an emergency such as the acute kidney failure or Poisoning Displays for dialysis. In the practical implementation of permanent dialysis, i.e. with classic dialysis patients, there are two options: outpatient dialysis or home dialysis. Outpatient dialysis patients are given a dialysis plan at the beginning of the therapy, which sets the dialysis dates per week.

A popular and useful scheme would be the dialysis schedule Monday-Wednesday-Friday, for example. To do this, the patient has to go to a suitable location at least three times a week. Hospitals can perform dialysis on an outpatient basis, but there are many places too Dialysis centerswho specialize in the treatment of this group of patients. Here, the latest development is increasingly being offered night dialysis, during which the patient can sleep. The aim is to influence the everyday life of those affected as little as possible. A dialysis session lasts on average about 5-6 hours. General parameters such as blood pressure, body weight and laboratory values ​​are recorded before each dialysis session. Then the shunt is pierced with two cannulas and the blood is cleaned. Then the patients return home.

A dialysis patient often notices significant fluctuations in their mood between cycles. Most people feel much better immediately after dialysis than shortly before, as undesirable substances have accumulated again after 1-2 days. The only way to get away from permanent dialysis is this Kidney transplant. Without this, dialysis is a lifelong therapy. In the case of acute or emergency dialysis, one or a few sessions are usually sufficient, since the kidney itself is still intact and only one poison or one cause had to be eliminated.

Complications

All in all, dialysis is a safe medical procedure with few complications. The most vulnerable component in dialysis therapy is the Shunt. As with all invasive interventions, there is a certain basic risk that a infection spreads what the worst case scenario sepsis can be. However, this risk is extremely small. More often it happens that the shunt is closed by the onset of coagulation: it forms in thrombus. In this case, the thrombus can be surgically removed by a surgeon. In the worst case, a new shunt must be placed elsewhere.Many dialysis patients have other underlying diseases, some of which can lead to secondary problems. So is in overhydrated patients with impaired Cardiac function ensure that the pumping power is adequate.

Because of the chronic Kidney disease It is particularly important to control the amount of water consumed during the day. The rule of thumb for the amount of water to be drunk per day applies to residual urine excretion plus 500ml. In addition, nutrition also plays a not insignificant role. Low protein meals are recommended because the body makes up many components of the proteins amino acids, converted into potentially toxic substances that the kidneys can no longer excrete. Here he plays nitrogen a crucial role from which the Neurons damaging ammonia arises. Even foods that contain a lot of potassium - bananas, kale, wheat germ - should not be consumed or only in moderation. A constant level of potassium in the blood is extremely important for normal heart work. So too high as well as too low potassium values ​​can cause the spontaneous occurrence of faulty heart actions to be responsible.

Overall, it can be said that dialysis is a low-complication and equally important measure that secures the life of a large number of patients with terminal kidney failure worldwide or bridges the time until a kidney transplant without unduly restricting the quality of life.