What is Hemodialysis (Extracorporeal dialysis)?

What is Hemodialysis (Extracorporeal dialysis)?

Hemodialysis (haemodialysis), also called kidney dialysis or just dialysis, is a treatment for acute kidney failure. Patients need dialysis if their kidneys are not working properly, i.e. they are no longer removing enough waste (such as creatinine and urea) and fluid from the blood. This usually happens when around 85-90 percent of kidney function is lost.

In order to perform the hemodialytic treatment, the blood of the patient is put in an artificial kidney which, through the pumping machine, circulates the blood through a filter that cleans it, and returns it back to the patient. Therefore, the blood needs to be extracted from the patient.

In urgent cases this is implemented by putting a catheter inside a big blood vessel (central venous catheter). In case the treatment could be scheduled in advance, the substitutional treatment is performed by arteriovenous fistula, which is a junction created surgically (using local anesthetic) between a vein and an artery, most frequently at the level of the forearm.

At the beginning of the dialytic session, the patient is connected to the hemodialytic machine by central venous catheter or by the insertion of two needles at the level of the fistula.

Every treatment lasts approximately 4 hours, and is done 3 times per week. The duration of every treatment and the weekly frequency could vary, depending on physician’s discretion based on clinical necessity of the patient.

The main point of the treatment is “the dialytic filter”, an element with bio-compatible dual compartment. Blood extracted from the patient flows in the first compartment. In the second compartment flows aqueous solution, enriched with solutions essential for the blood. This solution is also low in (or deprived of) waste that needs to be extracted and it’s called “dialytic solution”. To allow an adequate depuration, the blood flow through the filter is maintained with the help of a pump, with a flow rate of around 250-300 ml/min.

The amount of fluid, that is extracted during a single treatment, depends on the quantity of liquid that the patient takes in the interval between two consecutive sessions. Fluid intake is measured by weighing the patient at the end of the dialytic treatment and at the beginning of the following one. The “ideal weight” of the patient, called “dry weight”, is defined according to the clinical and instrumental data of the nephrologist who practices the dialytic treatment.

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