OBJECTIVE OF THE
• Describe how dialysis is used to treat
Types of dialysis.
• Give a detailed explanation of kidney
dialysis in terms of diffusion and
Detail explanation about main parts of
• Describe what happens during kidney
• List some of the drawback of kidney
Monitoring & Predialysis
Preserve Residual Renal Function
Control rising BP (Antihypertensive)
Control Renal Bone Disease (Ca2+, Vit.
Prevent/Treat Anaemia (Erythropoietin,
Dialysis (from Greek dialusis,
meaning dissolution, dia, meaning through,
and lysis, meaning loosening or splitting) is a
process for removing waste and excess water
from the blood, and is used primarily as
an artificial replacement for lost kidney function in
people with renal failure.
Dialysis may be used for those with an acute
disturbance in kidney function (acute kidney
injury, previously acute renal failure), or
progressive but chronically worsening kidney
function–a state known as chronic kidney
disease stage 5 (previously chronic renal failure
or end-stage renal disease).
The latter form may develop over months or
years, but in contrast to acute kidney injury is not
usually reversible, and dialysis is regarded as a
"holding measure" until a renal transplant can be
performed, or sometimes as the only supportive
measure in those for whom a transplant would be
Dr. Willem Kolff, a Dutch physician, constructed
the first working dialyzer in 1943 during the Nazi
occupation of the Netherlands. Due to the
scarcity of available resources, Kolff had to
improvise and build the initial machine
using sausage casings, beverage cans,
a washing machine, and various other items that
were available at the time.
Over the following two years, Kolff used his
machine to treat 16 patients suffering from acute
kidney failure, but the results were unsuccessful.
Then, in 1945, a 67-year-old comatose woman
regained consciousness following 11 hours of
hemodialysis with the dialyzer, and lived for
another seven years before dying of an unrelated
condition. She was the first-ever patient
successfully treated with dialysis.
Dialysis works on the principles of the diffusion of
solutes and ultrafiltration of fluid across a semi-
permeable membrane. Diffusion is a property of
substances in water; substances in water tend to
move from an area of high concentration to an
area of low concentration. Blood flows by one
side of a semi-permeable membrane, and a
dialysate, or special dialysis fluid, flows by the
A semipermeable membrane is a thin
layer of material that contains holes of
various sizes, or pores. Smaller solutes
and fluid pass through the membrane,
but the membrane blocks the passage
of larger substances (for example, red
blood cells, large proteins). This
replicates the filtering process that takes
place in the kidneys, when the blood
enters the kidneys and the larger
substances are separated from the
smaller ones in the glomerulus.
How does a Dialysis
Path which blood takes:
How the waste
substances in the blood
such as urea is removed
from the blood?
They are removed from the blood in the dialyzer.
In the dialyzer, the blood with waste products will
flow past one side of a semi-permeable membrane.
On the other side of this membrane, there is a
special substance called dialysate, which pulls waste
from blood. The waste such as urea will pass
through the membrane.
What is inside a
Dialysate is a solution that pulls waste from blood.
Types Of Dialysis
Peritoneal Dialysis (PD)
They work on similar principles: Movement of
solute or water across a semipermeable
membrane (dialysis membrane)
It involves diffusion of solutes across a
semipermeable membrane. Hemodialysis
utilizes counter current flow, where the dialysate
is flowing in the opposite direction to blood flow in
the extracorporeal circuit. Counter-current flow
maintains the concentration gradient across the
membrane at a maximum and increases the
efficiency of the dialysis.
In peritoneal dialysis, a sterile solution containing
glucose (called dialysate) is run through a tube into
the peritoneal cavity, the abdominal body cavity
around the intestine, where the peritoneal membrane
acts as a partially permeable membrane. The
peritoneal membrane or peritoneum is a layer of
tissue containing blood vessels that lines and
surrounds the peritoneal, or abdominal, cavity and
the internal abdominal organs (stomach, spleen,
liver, and intestines).
Diffusion and osmosis drive waste products and
excess fluid through the peritoneum into the
dialysate until the dialysate approaches
equilibrium with the body's fluids. Then the
dialysate is drained, discarded, and replaced with
Mechanism used for
Dialysis machine filter unwanted minerals from
blood by two means:
In Latin, "diffundere" means "to spread out".
Movement of solute across semipermeable
membrane from region of high concentration to
one of low concentration
The process of diffusion
Blood cells are too big to pass through the dialysis membrane,
but body wastes begin to diffuse (pass) into the dialysis solution.
Diffusion is complete. Body wastes have diffused through the
membrane, and now there are equal amounts of waste in both
the blood and the dialysis solution.
Made possible by osmosis
Movement of water across semipermeable
membrane from low osmolality to high osmolality
Osmolality – number of osmotically active
particles in a unit (litre) of solvent
The process of ultrafiltration in PD
Blood cells are too big to pass through the semi-permeable
membrane, but water in the blood is drawn into the dialysis
fluid by the glucose.
Ultrafiltration is complete. Water has been drawn through the
peritoneum by the glucose in the dialysis fluid. There is now
extra water in the dialysis fluid which need to be changed.
Main Parts of a Kidney
Dialysis Membrane (sometimes
referred to as simply a "dialyzer”) :-
Hemodialysis uses a cellulose-membrane tube
immersed in fluid, whereas peritoneal
dialysis uses the lining of the patient's abdominal
cavity (peritoneum), as a dialysis membrane.
Dialysate :- The dialysate (solution) has the
same solute concentrations as those in ordinary
plasma. Therefore if the patient's blood plasma
contains excess concentrations of any solutes,
these will move into the dialysate, and if the
blood plasma lacks the ideal concentration of
any solutes, these will move into the patient's
blood. Conversely, the dialysate fluid does not
contain any waste products such as urea - so
these substances in the patient's blood move
down the concentration gradient into the
Anticoagulant:-Heparin is the usual
anticoagulant that is added to the patient's
blood as it enters the dialysis machine (in
order to prevent the blood from clotting as
it passes through the machine). Preventing
the blood from clotting should, in turn,
prevent any blood clots from blocking the
filtration surface of the system. However,
heparin is not added during the final hour
of dialysis in order to enable the patient's
blood clotting activity to return to normal
before he/she leaves.
Pumps:- Peristaltic pumps are commonly
used for driving the various higher volume fluids
in the machine: blood, dialysate, water, and
saline. This type of pump is very convenient
because it does not touch the fluids directly.
Instead, a section of flexible tubing runs through
the pump mechanism where it is compressed by
rollers to push the fluid forward.
Valves:-Several valves with electronic
actuation are needed in the machine to allow
variable mixing ratios. Various implementations
are possible from simple opened/closed valves
driven by solenoids to precision variable-position
valves driven by stepper motors or other means.
Sensors:- Dialysis machines require many
different types of sensors to monitor various
parameters. Blood pressure at various points in
the extracorporeal circuit, dialysate pressure,
temperature, O2 saturation, motor speed, dialyzer
membrane pressure gradient, and air are all
monitored for proper values during dialysis
Cleaning system:- Between patient
sessions, any reused components must be
sterilized. One approach is to heat water or saline
to a high sterilizing temperature and then run it
through the machine, both through the
extracorporeal circuit and through the dialysate
Researchers are developing wearable artificial kidney
for dialysis patients which provides continuous dialysis 24
hours a day seven days a week, reported as upcoming
paper in the Clinical Journals of the American Society of
• The device essentially a miniaturized dialysis machine
,worn as a belt weights about 10 pounds and is powered
by two nine volt batteries .Because patients don’t need to
be hooked up to a full size dialysis machine ,they are free
to walk ,work or sleep while undergoing continuous ,gentle
dialysis that more closely approximates normal kidney
ADVANTAGE OF THE
Steady state metabolic and fluid control.
Reduce the need for phosphate-binder,
erythropoietin and hypertension medicine.
Peritoneal base dialysis, hence bloodless.
In-situ regeneration of spent dialysate in
Farewell to heavy dialysate bag storage ,
handling and disposal
Easy to travel to walk and to live.
Don’t need to visit dialysis facilities weekly.
Enhance lifestyle of the patient.
What happens during
I. Blood enters machine from body (under
pressure from radial artery).
II. Pump (some diagrams show a roller
pump) controls pressure and flow rate.
III. Anticoagulant added to prevent clotting.
IV. Blood passes through dialysis membrane
(equivalent to kidney nephrons).
V. Bubble Trap removes any gas bubbles
VI. Blood is filtered then returned to the
patient's radial vein
1. It is difficult to control the diffusion of
substances in a dialysis machine as well as in a
kidney so people on dialysis often have to
carefully control their fluid intake and diet.
2. Dialysis can involve a patient going to hospital
up to three times a week and being connected
up to the dialyser for about four hours at a time.
This could have a large impact on a person’s
Rapid changes in BP
fainting, vomiting, cramps, chest pain,
irritability, fatigue, temporary loss of vision
esp. in between sessions
more stringent with HD than PD
esp. in between sessions
Loss of independence
Problems with access
poor quality, blockage etc. Infection
(vascular access catheters)
Pain with needles
from the fistula during or after dialysis
during sessions; exit site infections;
blood-borne viruses e.g. Hepatitis, HIV
Responsibility:-Some kidney patients get tired of
the responsibility of doing their peritoneal dialysis
Body image:-Some peritoneal dialysis patients
find it difficult to accept a permanent PD catheter.
They worry that the catheter may affect their
sexual activity and their relationship with their
Fluid overload:-Fluid overload occurs when
there is too much fluid in the body.
Dehydration:-Dehydration occurs when there is
too little fluid in the body. It can be caused by
excess fluid loss due to diarrhea or sweating.
Discomfort :-Some PD patients find that having
the dialysis fluid in their abdomen is
Poor drainage:- is poor drainage of the dialysis
fluid among new patients. The most common
causes are: constipation and Catheter
Dialysis involves diverting the blood through
‘artificial kidney’ machine that cleans and returns
it to the body. During this process the blood is
purified by two principles (i.e. diffusion and
ultrafiltration) through a semipermeable
membrane. This semipermeable membrane can
be cellulose membrane(in case of HD) or it can
be peritoneal membrane(in case of PD).
In relation with this process of diverting
the blood through artificial kidney there
is some limitations that have to be
considered in order to perform safe
purification process. Generally this
machine gives hope for patients who
have renal failure.