Transcript Dialysis - DAISArchana

Outline the problems that arise from kidney failure and
discuss the use of renal dialysis and transplants for the
treatment of kidney failure
Kidney failure affects tens of thousands of people each
year in the UK
If one kidney fails, one can survive with one functioning
kidney
If both kidneys fail, death will result within about 2
weeks without medical treatment
Death often results from build up of potassium ions...
... which causes heart failure
Filters blood under pressure
Damaged
by
excessive
pressure
Adjusts pH of blood
Adjusts water
content of blood in
response to ADH
Selectively
reabsorbs glucose,
amino acids,
vitamins, sodium
and chloride ions
Reabsorbs water
NOTE: regulation of water balance helps regulate blood volume which helps
regulate blood pressure
Chronic kidney failure
Progressive, long term kidney failure – takes place
over a number of years
Possible causes:
- Bacterial infection of pelvis and surrounding tissue
- Nephritis: inflammation of glomeruli due to
antibodies to other infections attacking tissue
- Damage due to high blood pressure
- Damage due to obstruction of ureter, bladder or
urethra
- Diabetes mellitus (sugar diabetes)
- Atherosclerosis – reduces blood supply to kidney
Chronic kidney failure
Nephrons are progressively destroyed, leading to:
- Reduced quantity of urine
- Dilute urine
- Dehydration
- Salt imbalance
- Severe high blood pressure
- Coma and convulsions
Acute kidney failure
Relatively sudden failure of kidney
Possible causes:
- Loss of blood supply to kidney...
... possibly as a result of blood loss in accident ...
... heart failure...
... or toxic chemicals
- Severe bacterial infection or nephritis
- Physical damage to kidney
- Obstruction of ureters, bladder or kidney
Acute kidney failure
 Leads to:
- Little or no urine produced
- Accumulation of nitrogenous waste in blood
- Salt imbalance
- Pain
 Often reversible if treated QUICKLY
Dialysis
‘Renal Dialysis’
or
‘Haemodialysis’
Used to remove waste products such as urea,
excess ions such as potassium and excess water
from the blood when the kidneys are incapable of
doing this
Blood is passed
diverted through the
dialysis machine.
The dialyser contains
a semi-permeable
membrane made of
cellulose acetate or
nitrate (e.g. Visking
tubing)
Blood flows on one side of the dialysis membrane and a
dialysis fluid flows on the other side
Waste materials and excess salts and water diffuse across the
dialysis membrane into the dialysis fluid.
To patient
circulation
From patient
circulation
Dialyser
Trap
for
air
bubbles
Heater
Reservoir
of fresh
dialysis
fluid
Used
dialysis
fluid
The dialysing fluid is formulated to ensure that only waste
products and excess substances diffuse across the
membrane
Note: for diffusion to occur, there must be a concentration
gradient for the substance concerned to diffuse down
•The dialysing fluid contains no urea or other excretory
products, ensuring that these diffuse rapidly
A countercurrent system ensures that the
concentration of urea etc is always higher on the blood
side of the dialysis membrane
• The concentration of glucose, mineral ions and other useful
substances is the same in the dialysing fluid as in
normal blood plasma
These substances will only diffuse across into the
dialysis fluid if their levels in the plasma are above
normal levels
• The dialysing fluid also contains dextran – a polysaccharide
which cannot pass through the dialysing membrane
The level of dextran ensures that the water potential of
the dialysing fluid is the same as normal plasma
If the plasma contains excess water, this will move into
the dialysing fluid by osmosis.
If the blood and dialysing fluid flow in the same direction
(concurrent flow), then the concentration gradient between
adjacent regions of blood and dialysing fluid will drop as
diffusion takes place along the length of the dialysing
membrane
Flow
100
70
45
50
0
30
45
50
Diffusion
Gradient
Flow
This will cause the rate of diffusion to slow as we move
along the length of the dialysing membrane
In a counter-current system, the concentration gradient is
maintained along the length of the dialysis membrane
Flow
100
80
60
40
60
40
20
0
Diffusion
Gradient
Flow
Kidney transplants
 First kidney transplants were performed in 1960’s
 ~1800 transplants are performed each year in UK
 Number of transplants is limited by:
 availability of donors
 availability of good tissue match with patient
 Kidney transplants have high survival rates
 Tissue rejection is prevented with use of drugs such
as cyclosporin A which damp the immune
response
 As you only need one kidney, close relatives can act
as donors (reduces risk of rejection)
Kidney transplants
 Transplants are cheaper than dialysis
- Cost of dialysis was ~£20 000/year in mid 90’s
- Post-transplant drug therapy cost ~£3000/year
 Quality of life for patient is better if procedure is
successful