Dialysis is a very important therapeutic method, which saved or significantly prolonged life of many patients. It is a method that aims to “clean” the blood from waste products, which is implemented in acute or chronic renal failure. Very simply said, dialysis machine can be described as artificial kidney.


Classical dialysis is based on a semi-permeable membrane. The blood of the patient is lead through external tubes into the main apparatus, where the blood is filtrated through the membranes. On the other side of the membranes flows a dialysis solution, so-called dialysate. Blood cells do not pass through the membrane, but minerals and other minor substances do.


The dialysis solution is able to cleanse the blood and to accumulate its waste products and excessive amount of ions and other substances. In addition, the dialysis machine is able to get rid of excessive volume of water. After passing through the machine, the blood is brought back into the patient's body. Classical dialysis takes about 4 hours and it is usually repeated three-times a week.


The actual dialysis must be provided by a device that connects the patient's blood vessels to the external tubing of dialysis unit. In patients in acute condition, it is possible to insert a special dialysis central venous catheter (tube inserted into a large vein) that is connected to the tubes of the dialysis machine. In patients, who undergo a chronic dialysis program, it is advisable to contact a vascular surgeon who creates a special artificial connection between an artery and vein. This connection is known as AV shunt and it is usually created in a upper extremity. When you touch the skin above properly working shunt, we may feel a sound similar to purring cat. This means that the blood flows through the shunt. The shunt is punctured each dialysis and it serves for connection with the dialysis machine.


Due to repeated intravenous punctures and the need of passing the patient's blood through an external machine, which is used by more patients, chronically dialyzed people are preventively vaccinated against hepatitis B.


Dialysis is used mainly for patients in advanced stages of chronic renal failure. Acute dialysis, however, is also carried out in patients with acute renal failure and in certain intoxications when the harmful substance may be removed by the dialysis machine. Dialysis may help in solving acute heart failure, which does not respond to diuretics, because the machine can quickly remove the excessive amount of fluid from patient's body. Dialysis can be also used to correct some life-threatening disruptions of serum minerals and ions (hyperkalemia, hypercalcemia)


Chronic dialysis is not an ideal method. It saves lives, but it also carries a number of complications and risks. Dialyzed patients must often adhere to special dietary measures, especially reduced intake of water, which depends on the amount of urine they produce. Repeated punctures and overall weakened immune system threaten the dialyzed patients with infectious complications including sepsis and infective endocarditis. AV shunt may get occluded or they may cause too large increase or decrease of blood pressure during dialysis. Life with dialysis is not always easy, but it is a life.


Many patients are especially unsatisfied with the need to travel three-times a week to the local dialysis center and to be connected for hours to the dialysis machine. For younger people who are in overall good condition and who are able to cooperate, there is a handy solution known as peritoneal dialysis. It also has a number of disadvantages, but it may be performed at home by the patient alone.


Dialysis used to be a revolutionary method that allowed a mechanical device to replace kidney functions – temporarily, or permanently. This significantly improves the length and life quality of the patients. Severe cases of renal failure would die within days without the dialysis.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Contact: jiri.stefanek@seznam.cz
 Sources: basic text sources