module 2
How
Hemodiaylsis
Works
Your Guide to Home Hemodialysis
Module 2: How Hemodialysis
Works
6.0959 in
module 2
How Hemodialysis Works
By now you have learned that your kidneys are responsible for
many functions, including removing waste, regulating fluid
and electrolytes and producing hormones which help to create
red blood cells and regulate your blood pressure (BP). Diet and
medication play an important role in keeping you healthy, but
not as much as the dialysis treatment itself. It is also important
to look after your physical (exercise) and emotional well-being.
Refer to www.kidney.ca for more information.
How Hemodialysis
Works
Physical and
Emotional
Wellness
Hemodialysis is a medical procedure where blood is
artificially cleaned. Blood is pumped from your body
through your dialysis access (a needle or catheter
which is placed in your vein.) The blood travels
through sterile tubing and then into a dialyzer
(artificial kidney) where it is filtered. Clean blood
returns to you through your access.
Dialysis
Diet
Medication
How the Dialyzer Works
Blood Pump
Pressure Monitor
Anticoagulant
Blood removed to be cleaned
BLOOD
IN
dialysate out
Air Detector
Dialyzer (filter)
dialysate in
Pressure Monitor
Clean blood returned to the body
BLOOD
OUT
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
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How Hemodialysis
The dialyzer has two sections, one for blood and one for dialysate. Blood enters
Works
the blood section and flows through many tiny straw-like tubes. These tubes
have many tiny holes that allow waste products, electrolytes and fluid in your
blood to pass through the tubes into the dialysate section by two processes –
diffusion and ultrafiltration. Red and white blood cells and proteins are large and cannot pass
through the holes. The dialysate is made up of water and concentrated electrolytes and is mixed
inside the dialysis machine. The dialysate passes through the dialyzer around the outside of the
tubes where it collects the wastes and fluid from the blood, exits the dialyzer and goes down
the drain. This process takes place many times throughout your treatment depending on how
long you dialyze and how fast the blood is pumped through the tubing.
Dialysis replaces many of the functions that your kidneys are no longer able to do for you:
• Removes salt and water (helps to regulate your BP)
• Cleans the blood by removing wastes (eg. urea, creatinine)
• Regulates electrolytes and minerals (eg.calcium)
• Provides an opportunity to easily give medications to replace some hormones
Machine Features
There are many hemodialysis
machines available but all have
similar features. Your clinic will
teach you the specific functions for
your machine as well as provide
you with detailed instructions to
follow. It includes many pumps
and sensors in both the blood and
dialysate (fluid) circuit to enable
dialysis to take place. Since safety is
the most important feature of your
equipment, it includes ongoing
monitoring and alarm systems
to alert you of any concerns.
Your training will make you very
comfortable with operating the
dialysis machine prior to initiating
home hemodialysis.
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
Normal Saline
Blood Pump
Arterial
Pressure Monitor
Venous
Pressure Monitor
Heparin Pump
Dialyzer
Venous
Line Clamp
Air Detector
Dialysate
Concentrate
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Water Treatment How Hemodialysis
Works
You previously read that water mixes with the concentrated electrolyte
solution to create dialysate. Even though the dialysate does not actually mix
with your blood it is vital that purified water is used as the mixture comes into
contact with the blood as it passes by the tiny holes in the tubes.
You may receive chlorinated water through a utility company but it still
requires additional purification. Water contains bacteria and minerals as well
as chlorine which all must be removed prior to entering the dialysis machine.
This is done by using a reverse osmosis system and/or de-ionization system
and carbon tanks. In addition some water may also require an ultraviolet light
and a water softener. This is more likely to be required if you are using a well
for your water supply.
When your home is inspected, in preparation for
installation of the equipment, water samples will
be taken to enable your clinic to determine what is
required. Your water will also be regularly tested to
ensure it is safe for use in your treatment. You will be
instructed in the proper operation and care of the
water system as this is a very important part of your
treatment. Failure to do proper maintenance can lead
to serious harm.
If your community issues a “Boil Water Advisory”,
contact your unit. They will tell you if it is safe to
dialyze at home or not.
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
SAMPLE
PURE WATER
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Vascular Access
How Hemodialysis
Works
If you are starting dialysis in the next few months your healthcare team will
already have initiated discussion around vascular access. This means having an access to your
vein created which is necessary for hemodialysis to occur. It is very important to have a properly
functioning access to allow for adequate blood flow so that you get the most benefit from your
treatment and do not have any machine alarms.
There are three types of vascular access:
Access
Needles
Vein
Artery
Looped
Graft
Vein
Artery
Catheter
Access
Needles
Internal
Jugular
Vein
Arteriovenous fistula (AV fistula)
An AV fistula is created when an artery is surgically
connected to a vein in the lower or upper arm. Pressure
from the arterial flow causes the surface vein to
enlarge and blood flow to become stronger. This is the
preferred access as it usually lasts longer and has fewer
complications. A fistula may take two months or longer
to be ready for use. Two needles are used during each
treatment.
Arteriovenous graft (AV graft)
An AV graft is used if your veins are too small for an AV
fistula. An artery in your lower or upper arm is connected
to a vein using a synthetic tube. It is then tunnelled
under the skin as a loop or straight tube.
An AV graft can be used a few weeks after surgery once
the swelling has gone down. This is the secondary option
for access as it can be prone to infection and clots.
Two needles are used during each treatment.
Central Venous Catheter (CVC)
A CVC is a soft, flexible tube usually inserted into a large
vein in your neck. The tip of the catheter rests in the right
atrium (an upper chamber in the heart). The tube consists
of two channels - one port to allow blood to be pumped
out of the body and the other as a return port. An exit site
is where the tube comes out of the body to allow access to
the ports. This access can be used immediately but is not
preferred as it offers a greater risk of infection and clotting.
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
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Caring for an Arteriovenous Access AV fistula and AV graft
How Hemodialysis
Works
Proper care of your dialysis access is very important as it is essential for your dialysis treatment.
You should check your access every day and inform your clinic or nurse on call if any problems are
found.
1. Feel for the thrill which is the vibration of the blood as it flows through your fistula or graft.
A decrease or absence of the thrill can be an indication of a blood clot.
2. Listen for the bruit by putting your arm up to your ear or by using a stethoscope. It is important
that you know what it usually sounds like. If you hear a whistle or a decrease in the strength of
the sound this could indicate a narrowing has occurred.
3. Check for signs of infection including swelling, redness, pain or discharge from needle sites. You
could also have a blood stream infection which may include fever, chills (on or off dialysis), or a
general feeling of unwell.
4. Prevent infection by always following your clinic’s instructions for preparing your access –
proper hand washing and cleansing of the site.
5. Do not put prolonged pressure on your access that could restrict the flow and cause it to clot.
This includes tight clothing, jewellery or sleeping on your access.
6. Do not allow your access arm to be
used for any blood pressure tests,
venipuncture or intravenous lines
unless directed by your
healthcare team.
7. Report any numbness, pain,
discolouration or coldness of the
hand on your access arm, which
could indicate a decrease in
blood flow.
AV fistula
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
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Caring For Your Central Venous Catheter (CVC)
How Hemodialysis
Works
Whether your CVC is being used as a temporary or permanent access for your treatment, it is
important that it be properly cared for. The catheter has two ports, one to allow dirty blood to be
removed and the other to allow clean blood to return. Following treatment each port is filled with a
locking solution to prevent blood from clotting inside the catheter. This solution is removed at the
start of each treatment.
1. Always wash your hands as directed when handling your catheter as infection is one of
the most common problems and may result in hospitalization and catheter replacement.
Check your catheter exit site every day and report any drainage, pain, redness, swelling
or odour to your clinic.
2. Do not pull on your catheter which could result in it being pulled out especially if it is
new. If it falls out (rarely), apply direct pressure to the exit site for at least 15 minutes or
until bleeding stops, cover with a dressing and call 911, your clinic, or go to your nearest
Emergency Department.
3. Change your dressing regularly as directed by your
clinic.
This is especially important if it gets wet.
4. Follow your clinic’s direction regarding
showering and bathing.
5. Make sure clamps remain closed when not in use.
6. Report any pain or swelling in your neck or arm
on the side in which the catheter is inserted.
This may indicate a clot has occurred.
7. Do not let anyone access your catheter unless
directed to do so by your healthcare team.
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works
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Changing Your Catheter Exit
Site Dressing
How Hemodialysis
Works
Your dressing should be changed at least once per week, or more often as required - especially if
the dressing gets wet. Some clinics may allow you to go without a dressing once the exit site is well
healed (shower technique) but it is important that you check with your clinic first.
Supplies:
• Face mask
• Two chlorhexidine gluconate swab sticks
(or alternate as directed by your clinic)
• Dressing
• Alcohol based hand rub (ABHR)
Procedure:
1. Put on your face mask and wash your hands.
2. Remove dressing and observe exit site – report
redness, drainage, swelling or odour to your unit.
3. Use ABHR
4. Partially open swab sticks
5. With one swab stick, wipe around the exit site in a
circular motion going away from the exit site.
6. Repeat with second swab stick cleaning from the exit
site along the catheter to the clamps.
7. Allow to air dry for a minimum of two minutes
8. Apply antibiotic ointment to exit site if directed
9. Apply new dressing
!
IMPORTANT POINTS TO REMEMBER ABOUT YOUR ACCESS
LOOK, LISTEN AND FEEL
WASH YOUR HANDS
CALL YOUR CLINIC IF CONCERNED
Your Guide to Home Hemodialysis | Module 2: How Hemodialysis Works