Dialysis

Dialysis (Greek διάλυσις dialysis, resolution ') is a blood purification method as a replacement method is used in renal failure. Dialysis is the most important addition to the kidney renal replacement therapy in chronic renal failure and one of the treatment options for acute renal failure.

Under dialysis is here understood to mean a mass transfer across a membrane, wherein a dialysis solution is applied on one side of blood / plasma, and on the other side of the membrane.

The world's first " blood washing " through semi-permeable membranes in humans was carried out in 1924 by Georg Haas in casting. The breakthrough came, however, only Willem Kolff 1945 in Kampen (Netherlands) with his drum dialyzer with cellophane tubing as a dialysis membrane. This membrane allowed a controlled blood purification of defined quantities. A technically superior parallel development of Nils Alwall in Lund (Sweden) in 1946 permitted the washout of edema fluid from the lungs and tissues (ultrafiltration ).

More about the technology of dialysis see dialyzer.

Dialysis method

It can be distinguished extracorporeal ( outside the body ) and intracorporeal taking place ( within the body ) method. The most common method is extracorporeal hemodialysis, hemodiafiltration and hemofiltration in addition be applied. The non- extracorporeal methods is peritoneal dialysis. Both methods are in Germany in chronic renal failure in the ratio of 20: 1 was carried out. The extracorporeal procedures include the hemoperfusion ( in certain acute poisoning ) and apheresis procedures were, however, no renal replacement therapy, but the treatment of other medical conditions ( eg, liver replacement therapy ) may be used. As a detailed knowledge of the potential side effects are necessary for carrying out the method, these are mostly used by nephrologists or intensivists.

Hemodialysis

Here, according to the principle of the concentration equalization small molecular substances of two liquids which are separated by a semipermeable membrane ( osmosis). Separated from the filter membrane is on the one hand blood with nephrotoxins, electrolytes such as potassium and phosphate and urinary metabolites (such as urea, uric acid). On the other side of the membrane there is a germ-free, recycled solution ( dialysate), whose water was prepared by reverse osmosis for online preparation containing no waste products and has a geared to the individual needs of the patient proportion of electrolytes. The semi-permeable filter membrane (dialysis membrane) between blood and dialysis solution has pores that small molecules such as water, electrolytes and harnpflichtige substances to pass through, but hold back large molecules such as proteins and blood cells.

Prerequisite for the implementation of hemodialysis is a sufficient circulation stability, a sufficient volume of blood and a good ( arterial, venous ) access to the patient. The latter is achieved by the operating system of a arterio-venous shunts (former external Scribner - shunt, today usually internal Cimino shunt) to the lower or upper arm. For problematic own vessels while also vascular grafts ( Goretex ) are used. In very rare cases, the shunt on the thigh or between the subclavian artery and the subclavian vein is ( because of the location and necklace or neckline Hunt called ), applied with or without the use of artificial vessels. Another possibility is the introduction of a dialysis catheter into a suitably sized Körpervene for acute dialysis ( Shaldon catheter, usually on the neck ( internal jugular vein ) or the supraclavicular fossa ( subclavian vein ) rarely have the bar ( femoral vein ) ), lasting only for multi-morbid patients with very poor vascular situation or severe heart failure ( Demers atrial catheter or Hickman catheter).

During treatment is pumped through the patient access device from the patient's blood in the dialyzer (filter) past the dialysis membrane and cleaned back to the patient. Toxins ( metabolic breakdown products ) and low molecular weight substances ( membrane-permeable substances ) are conveyed from the blood by concentration gradients (diffusion) through the membrane to the other side of the filter in the dialysis solution ( dialysate) and thereby removed. The dialyzer is constantly fresh dialysate flows through ( about 500 ml / min). The hemodialysis treatment is usually about 4-5 hours ( overnight dialysis to 8 hours) per treatment and at least three times a week carried out (depending on body weight, residual renal function, cardiac output ). Patients who perform home hemodialysis, avoid the problematic longer treatment interval on weekends and dialyze more frequently, usually every other day or daily.

Patients with chronic renal failure often also suffer from over-watering. The excess water is removed from the blood ( negative pressure to the dialysate ) by applying a pressure gradient. This regulates how much fluid is removed from the blood and hereby mimicked the natural diuretic function of the kidney. The liquid withdrawal, however, is limited by the fact that in the body of the liquid ( also applies for the toxins ) can not be arbitrarily fast re-diffuse into the bloodstream to compensate for fluid loss, creating a life-threatening drop in blood pressure threatened. Also, give different tissue fluid at varying tempos, so there may be a spasm of the muscles, for example, even though there is too much fluid in the body. Due to these effects, the achievable fluid removal is limited by the dialysis and patients should not therefore drink at will. On the other hand, many patients suffer due to the accumulation of uric substances in the body under constant strong thirst, low fluid intake allowed (residual excretion in 24 hours plus 500 ml ) is often perceived as stressful.

An extension of the dialysis time is mainly due to the daily home hemodialysis (HHD ) is possible and allows a more uniform treatment. Since the dialysis efficiency is highest in the first half of treatment, it is medically useful, but rarely practiced to carry out frequent but short dialysis instead of rare, longer dialysis. With the daily hemodialysis advantages of peritoneal dialysis are (dialysis every day) and conventional hemodialysis ( high efficiency ) combined. For patients who have no possibility of home hemodialysis, the night dialysis offers in the center, to extend the time of dialysis. Some patients can sleep during dialysis, sometimes after an acclimatization period, others, however, not at all. Due to the practicality and patient acceptance, partly because the health insurance basically only pay packages per patient for treatment, more frequent dialysis is not offered as three times per week for patients who have no way to HHD. Exceptions to these additional dialysis fluid overload in order to reduce the " dry weight " of the patient, or the phase of the dialysis recording, in which the patient is dialyzed daily for a week under certain circumstances.

Hemofiltration

In hemofiltration fluid is withdrawn from the blood, is used without a rinsing solution ( dialysate). Due to an applied pressure gradient over a pump ( TMP ) of the filter membrane is convectively plasma fluid out of the blood withdrawn through the membrane (ultrafiltration ). This transmembrane flow all filterable substances are also removed. This allows a slow detoxification and if necessary a rapid volume change in the patient's body. The extracted liquid is replaced by an electrolyte solution ( Substituate ). This is an automated procedure.

As spontaneous filtration is a procedure that is squeezed liquid plasma in which the natural pressure of an artery of the patient circuit ( without pump) and replaced by an electrolyte solution: Continuous arteriovenous hemofiltration ( CAVH ). This little effective and dependent on the blood pressure method was soon replaced by the pump -driven venovenous hemofiltration continuous ( CVVH ), which was in turn enhanced by the combination with dialysis for continuous veno-venous hemodiafiltration ( CVVHDF ). These methods are used in intensive care stations for the treatment of patients with acute renal failure.

Hemodiafiltration

The hemodiafiltration called an extracorporeal blood clearance technique, in which hemodialysis and hemofiltration are applied in combination. This process is especially suited for use in chronic renal failure and enables both the removal of low - and medium -molecular-weight substances under controlled replacement of the ultrafiltrate by physiological electrolyte solution ( dilute ). The replacement solution is added to the blood either before or after the dialyzer and the dialyzer removed (ultrafiltration ). This allows a higher transmembrane flux to be generated, which leads to more effective removal of toxic substances.

Hemoperfusion

The hemoperfusion is not a renal replacement therapy, but a method of treatment in cases of acute poisoning and is performed only by specially established for this purpose clinics. The blood is pumped through adsorbents (such as activated carbon or ion exchange resins ) characterized some fat-soluble or protein-bound substances (eg certain overdosed drugs, organic solvents, insecticides, fungal toxins ) can be removed from the blood. The method has been established only for a relatively small number of substances.

Peritoneal dialysis

Peritoneal dialysis (PD ) is also known under the term peritoneal dialysis. There are different PD methods, for example manual CAPD (continuously ambulatory peritoneal dialysis, continuous ambulatory peritoneal dialysis ), and the methods carried out with devices of CCPD ( Continuous Cycling PD) IPD ( intermittent PD) NIPD ( Nightly Intermittent PD ), etc. the choice of method depends inter alia on the transport characteristics of the peritoneum (see below), and underlying disease of the patient.

The peritoneum ( the peritoneum ) is a serous membrane that lines the abdominal cavity and covered large parts of the intestine. It is a relatively well- perfused tissue, for example, plays an important role in the immune defense of the body.

Due to the specific construction, the peritoneum may also be used as a " filter membrane ": For this purpose, the patient tube (catheter ) is implanted into the abdominal cavity. About this catheter dialysis solution is introduced into the abdominal cavity and there for several hours (eg CAPD) or for 20-30 minutes left (eg IPD). The small molecular weight substances can now step out of the blood through the capillaries of the peritoneum into the dialysis solution as a concentration gradient exists. If the body in this way and liquid (water ) is to be removed, the dialysis solution has a higher content of soluble substances have as the blood. For this purpose, it is enriched with glucose, dextrins or other substances (experimental). The dialysis solution has to be drained off (normally four to six hours at CAPD) and replaced by a fresh, after a certain time. In contrast to the artificial membrane for blood dialysis, the peritoneum is quite permeable to proteins, thereby leading to a loss of relevant protein. Advantages of this method are: the longer maintaining the residual renal function, the total rarer complications of dialysis access and the protection of the circuit, which also allows for very old and cardiac patients renal replacement therapy. Another possible advantage is the degree of independence of patients from a dialysis center: In aptitude can perform dialysis at home, and leisure travelers are uncomplicated possible because the materials are delivered directly to the resort and eliminates the appointments with a holiday dialysis center. Peritoneal dialysis is a disadvantage of the risk that the abdomen becomes infected with a possible contact with the environment of the pathogenic microorganisms, with the result of peritonitis. Therefore, patients must work very carefully and as sterile as possible when changing solutions. Limited, the method is due to its comparatively lower efficiency by the body weight and the residual renal function - is the body mass increases and the residual renal function low, the PD is less. In the course of treatment, especially greater glucose-containing dialysis solutions over several years, it comes in some patients to change the peritoneum, which at the same glucose concentration decreasing or even negative filtration performance has resulted. Then the concentration of glucose must to avoid edema and high blood pressure increases in the dialysis solution and the residence time of the solution are reduced in the abdomen. Due to the changes of the peritoneum, which in most cases result in a very variable period of time at some point to a so-called ultrafiltration failure and thus insufficient detoxification and drainage, the Peritonealdialse is always a process on time. Good experiences you do with peritoneal dialysis as a " bridge to transplant " in younger people. The current uptake of glucose from the dialysis solution and the continuous loss of protein can lead to the development or exacerbation of diabetes mellitus. Nevertheless, in studies it could be shown that especially diabetics benefit in the early years of dialysis on peritoneal dialysis ..

Beginning of dialysis therapy ( hemodialysis )

The decision whether and when a dialysis treatment or hemofiltration in patients with renal failure is required, depends on various factors, which may be acute or chronic in nature.

• Acute indications for the start of dialysis treatment:

• Chronic causes of the onset of dialysis treatment: