Our kidneys help to purify and clean our blood by eliminating excess fluid, minerals, and wastes. They also produce certain hormones that keep our bones firm and strong and our blood healthy. However, when our kidneys fail, dangerous wastes get accumulated in our body, our blood pressure may increase, our body may retain excess amount of fluids and not make sufficient red blood cells.
Hemodialysis is the most common method used for the treatment of permanent kidney failure. Hemodialysis is a complicated therapy that necessitates a joint and coordinated effort from the entire health care team, including the nephrologist, urologist, dialysis nurse, technician, dietitian, and social worker.
How Hemodialysis Works
In this procedure, a few ounces of your blood are allowed to flow at a time, through a uniquely designed filter, which helps to remove harmful wastes and extra fluids. The purified blood is then returned to the body. Eliminating the dangerous wastes and excess amounts of salt and fluids helps keep your blood pressure under control and maintains the proper balance of chemicals such as potassium and sodium in your body.
During the course of hemodialysis, most patients have to go to a clinic or a dialysis center three times a week for 3 to 5 hours.
Vascular Access for Hemodialysis
One of the most important steps prior to starting hemodialysis is preparing a vascular access. Vascular access refers to a particular site on your body from which your blood could be removed and returned. A vascular access is often prepared several weeks or months before the hemodialysis is started. A major advantage of vascular access is that it enables easier and efficient removal and replacement of blood with very less complications.
The three important types of vascular access for hemodialysis are an Arteriovenous (AV) fistula, an AV graft, and a Venous catheter.
A fistula is essentially an opening or connection between any two regions in the body that are separate.
An Arteriovenous fistula (AV) fistula is connection between artery (Blood vessel carrying pure/oxygenated blood) and vein (Blood vessel carrying impure/deoxygenated blood). AV Fistula is greatly useful as it increases the strength of the vein and facilitates easy access to the blood system. The AV fistula is regarded as the best long-term vascular access for hemodialysis as it ensures sufficient blood flow, lasts for a longer period of time, and has fewer complications than other types of access.
An AV fistula requires cautious advance planning as a fistula often takes some time after surgery usually 4-6 weeks.
Connecting an artery directly to a vein, quite often in the forearm, creates an AV fistula. This enhances the flow of blood into the vein. In due course, the vein grows larger and thicker. This in turn makes repeated needle insertions for the dialysis easier. The surgery is performed using a local anesthetic.
If there are small veins that won’t develop into a fistula, a vascular access, which connects an artery to a vein, is created with the help of a graft or a synthetic tube implanted under the skin in your arm. The graft acts as an artificial vein that can be repeatedly used for the placement of needle and blood access during the process of hemodialysis. A graft could be used soon after placement, often within a period of 2 or 3 weeks.
In general grafts do not perform as well as fistulas; that is why they are always a second option. However, many times they may serve a patient’s needs better, particularly when multiple fistulas are failing.
Grafts have a lifespan of approximately 2 to 3 years but can often last longer. Forearm loop grafts can eventually help the arm veins grow large enough (mature), so that when the graft goes down, a fistula creation may be feasible.
The main drawbacks of a graft include the high infection risk and the higher risk of clots and subsequent re-interventions.
Venous catheter for temporary access
In certain cases, if the kidney disease has progressed rapidly, you may not get sufficient time to get a vascular access before the treatment begins. In such conditions, you may have to use a venous catheter as a temporary access so as to initiate dialysis immediately.
A catheter is basically a tube, which is inserted into a vein in your neck, chest, or leg near the groin. A catheter comprises two chambers that enable a two-way flow of blood. Once a catheter is in place, needle insertion is not required.
However, catheters are not suitable for permanent access. They can get clogged, become infected, and even result in the narrowing of the veins in which they are placed. But if hemodialysis has to be started immediately, a catheter can be used. It can function properly for several weeks or months.
Every hemodialysis session makes use of an AV fistula or an AV graft that necessitates needle insertion. Most often two needles are used; one to transport blood to the dialyzer and one to return the purified blood to your body.
Risks/ complications of vascular access
The most common complications are:
- Access infection and reduced blood flow owing to clotting of blood in the access
- Venous catheters tend to develop infection and clotting issues that may require proper medication and removal or replacement of the catheter.
- • AV grafts can also develop reduced blood flow. This is in fact an indication of clotting or narrowing of the access. In such a situation, the AV graft may need angioplasty, a procedure that helps to widen the small portion or region that is narrowed. Yet another option is to replace the narrowed segment through surgery on the AV graft
Taking care of vascular access
Here are some steps you can take to protect your access:
- Ensure that your nurse or technician examines your access prior to each treatment.
- Ensure that your access is clean at all times.
- Your access site should be used only for dialysis.
- Ensure that you do not accidentally bump or cut your access.
- Do not allow anyone to put a blood pressure cuff on your access arm.
- Please do not wear jewelry or tight clothes over your access site.
- Never sleep in a position where your access arm is under your head or body.
- Never lift heavy objects or put too much pressure on your access arm.
- Please check the pulse in your access every day.