Dialysis

Hemodialysis

In hemodialysis, blood is purified with the help of dialysis machine and dialyzer.

Most of the time, hemodialysis is performed in hospitals or free standing dialysis centers, under the care of doctors, nurses and dialysis technicians.

• The dialysis machine pumps blood from the body to the dialyzer through flexible blood tubings. Heparin infusion or continuous saline flushing is done to prevent clotting of blood.

• The dialyzer (artificial kidney) is a special filter through which blood flows which removes extra fluids and waste products. Dialyzer purifies blood with the help of special solution called dialysate which is prepared by a dialysis machine.
• Once the blood is cleaned, the machine sends it back to the body.
• Hemodialysis is carried out usually three times per week and each session lasts for about four hours.

The three most common types of vascular access for hemodialysis are central venous catheters, native arteriovenous (AV) fistulas and synthetic grafts.

As soon as the decision to start immediate hemodialysis is made, a vascular access or central venous catheter has to be inserted. The vascular access will allow the blood of the patient to leave the body and be brought to the artificial kidney or dialyzer to be cleaned or filtered.

This method of vascular access is ideal for short-term use until a fistula or graft is ready.

A catheter is inserted into a large vein in either the neck, chest, or leg near the groin (internal jugular, subclavian and femoral veins respectively). With this catheter more than 300 ml/min blood can be withdrawn for dialysis.

Catheters are flexible, hollow tubes with two lumens. Blood leaves the patient’s body passing through one lumen, enters the dialysis circuit, and is returned to the body via the other lumen.

Venous catheters are immediate but temporary accesses for hemodialysis especially on emergency cases.

Two types of venous catheters are available, tunnelled (usable for months) and non-tunnelled (usable for weeks).

The arteriovenous or AV fistula is the most common and the best method of vascular access for long term hemodialysis because it lasts longer, & is less likely to get clotted or inflected.

An AV fistula is created in the forearm near the wrist by surgically connecting or apposing the radial artery to the cephalic vein.

Since blood flow and pressure is higher in the artery than the vein, blood flows from the former to the latter. After a few weeks or months, the vein dilates and its walls thickens.

Such maturation of the AV fistula takes time, hence, it cannot be used for hemodialysis immediately after its construction.

For hemodialysis two large-bore needles are inserted into the fistula, one to carry blood to the dialyzer and the other to return the cleansed blood to the body.

AV fistula lasts for many years if maintained well. All usual daily activities can be easily performed with the hand having AV fistula.

• Life of a patient with CKD- ESKD depends on regular and adequate hemodialysis. The AV fistula is the permanent vascular access essential for chronic hemodialysis and is also called the lifeline for the patient on maintenance hemodialysis. Special care of AV fistula ensures adequate blood delivery for a long period.
• Large amount of blood with high pressure flows in the veins of AV fistula. Accidental injury to such dilated veins can lead to profuse bleeding, and sudden loss of blood in large volume can be life threatening. So special care is mandatory to protect veins of AV fistula.

Proper regular care and protection of AV fistula ensures adequate blood delivery for years. Important precautions to keep a fistula healthy and working for longer period are as follows:

Always keep the site of the fistula clean by washing the vascular access arm daily and before each dialysis treatment. It is also important to observe aseptic technique during cannulation and throughout the dialysis process.

AV fistula is the “lifeline” in patients of CKD, without which long term hemodialysis is not possible.

• Use access site only for dialysis. Do not let anyone give intravenous injections, draw blood or measure blood pressure on the arm with the AV fistula.
• Avoid injury to AV fistula. Don’t wear jewelry, tight clothes or a wrist watches on the vascular access arm. Accidental injury to AV fistula can lead to sudden profuse bleeding, which can be life- threatening.
• To control bleeding, immediately apply firm pressure at the site of the bleeding with the other hand or with a tight bandage. After the bleeding is controlled, contact your doctor. Instead of making efforts to control the loss of blood, rushing to hospital for help is unwise and dangerous.
• Do not lift heavy items with the accessed arm and avoid pressure on it. Be careful; do not sleep on the arm with the A V fistula.

Blood flow through the AV fistula should be checked regularly by feeling the vibration (also called a thrill) three times a day (before breakfast, lunch and dinner). If the vibration is absent, your doctor or dialysis center staff should be immediately contacted. A blood clot may have formed inside the fistula and early detection and timely intervention to dissolve or remove the clot may salvage the AV fistula.

• Low blood pressure carries the risk of failure of AV fistula, and therefore, should be prevented.

Regular exercise of AV fistula can lead to its maturation. Even after

initiating hemodialysis, regular exercise of access arm helps to strengthen the AV fistula.

• An arteriovenous graft is another form of long term dialysis access, which can be used when persons do not have satisfactory veins for an AV fistula or have a failed AV fistula.
• In graft method, an artery is surgically connected to a vein with a short piece of synthetic soft tube which is implanted under the skin. Needles are inserted in this graft during dialysis treatment.
• Compared to an AV fistula, AV grafts are at a high risk to develop clotting, infection, and usually do not last as long as a fistula.