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Dialysis is a process through which chemicals in higher concentrations are extracted into a fluid with low or no concentrations of those chemicals, through a membrane that allows those chemicals to pass through.
In patients with kidney failure, the kidneys are unable to clear the blood of various chemicals that accumulate in the normal course of day to day activities. Therefore, such normal chemicals accumulate to very high levels in the blood. This alters the character of the blood. [For a better understanding as to what the kidneys do normally please read 'what do kidneys do' and 'How do kidneys work.'] Those chemicals could be extracted through such a process called dialysis. The fluid that is used to extract those chemicals is called Dialysate. There are two membranes available for this purpose. One is the natural membrane that surround the stomach, intestines and colon. This membrane is called Peritoneum. When the peritoneum is used for dialysis, then the procedure is called PERITONEAL DIALYSIS. When artificially made synthetic membranes are used where the blood is brought out of the body to be processed, then it is called HEMODIALYSIS. Since the hemodialysis requires the synthetic membrane to be constructed into an artificial kidney it is also called ARTIFICIAL KIDNEY TREATMENT. When compared with each other, there are advantages and disadvantages with either of these procedures.
Hemodialysis is one of the two methods of dialysis used to treat
the patients with kidney
failure (Uremia). In this method, the blood is drawn from the patient and
circulated on one side of a synthetic membrane and the dialysate on the other side.
During that time the various toxic chemicals are drawn by the dialysate from the blood
across the membrane. The membrane is needed to keep the blood from being contaminated and
not to allow the dialysate extract other essentials from the blood. The dialysate is
then discarded. This is a continuous process done over a period of 3 to 4 hours at a
time and usually 3 times a week.
Excess body fluid from the blood also will be forced
out through the membrane into the dialysate to be discarded.
During hemodialysis, as well as peritoneal
dialysis, the excess fluid in the body also could be removed. By removing excess
fluid and the toxic chemicals, the internal
chemical environment of the body is restored towards normal.
Concentrated
Dialysate and purified water is pumped into proportioning unit and appropriate Dialysate
is generated and pumped into the Dialyzer. Blood from the patient is pumped into the Dialyzer in the opposite direction. The dialysate with high concentration of extracted toxins is discarded. Blood with lot less toxin is returned to the patient. |
Several months or weeks before the patient requires hemodialysis, an access to the patient's blood vessel is created. This is accomplished by connecting two of patients own blood vessels together so that the amount of the blood will be adequate to run through the artificial kidney. Usually these are the artery and the vein in the arms. This type of access is called 'A-V Fistula'. When there are no such blood vessels are available (inadequately developed veins) then an artificial blood vessel will be placed under the skin, with one end connected to an artery and another end connected to a vein. Such vascular access is called 'AV-Graft'. Whether it is AV-Fistula or the AV-Graft, the necessary surgery will have to be done several weeks or months ahead, since they cannot be used as soon as they are created.
When the fistula or the graft is ready to be used, two needles are
inserted into the fistula or the graft and the patient will be connected to the
Artificial Kidney. Then the Artificial Kidney draws the blood (at times 500 cc/ min)
processes it and then returns it to the patient with lot less chemical toxins. This
is done continuously for 3 to 4 hours at a time - usually three times a week. During the
hemodialysis patient's blood will be 'thinned out' (anticoagulated) so that it
will not
clot and clog the artificial kidney.
Although the elderly patients may be admitted to the hospital for close monitoring of the initial dialysis treatments, hemodialysis does not require the patient to stay in the hospital. Most of the time, esp., in chronic renal failure it is done as an out patient procedure.
In patients with chronic renal failure, the chemical changes in the
blood have occurred over a long period of time. This gives their bodies time to
adapt to the changes and still function reasonably well. During initial few weeks (or
months) after starting hemodialysis treatments, patients may not feel well. In fact,
rarely, some patients may even feel that the treatment is making them more ill.
This is because the hemodialysis causes rapid changes in their body chemistry. The
body need to readjust and equilibrate to the new chemical environment. This
reorientation or stabilization might require several weeks to few months. During such
stabilization patient might experience
* Nausea / vomiting
* Weak and tired
* Wide fluctuations of the blood pressure
* Headaches, Muscle cramps
* In severe cases: tremors of the arms and legs, confusion,
disorientation and even convulsions.
* When any one or a combination of the above symptoms occur
it is then called 'Disequilibrium
syndrome'
To minimize these symptoms of 'disequilibrium syndrome', usually the dialysis treatments are started with low intensity. Over a period of several weeks the treatments will gradually be intensified.
WHAT ARE THE COMPLICATIONS OF HEMODIALYSIS:
As with all medical procedures there are
complications that might occur during hemodialysis. Due to routine precautions that
are taken, most of such complications are prevented. When they do
occur most of them could be treated successfully.
Some such complications are:
* Infection
* Loss of blood
* Contamination
* Low blood pressure (Hypotension)
* Muscle cramps
* Nausea / Vomiting
* Itching
* Irregular heart beats/palpitations
* Problems related to malfunction of the dialysis machine:
- Blood leak due to ruptured membrane
- Air embolism (Air bubbles getting into the blood vessels)
- Breaking of Red Blood Cells (Hemolysis)
- Hypo or Hyperthermia due to improperly warmed dialysate
* Clotted AV-fistula or the AV-Graft requiring surgery or other
interventions
Adequate 'quantity' of dialysis needed per patient depends on several factors. The calculation of adequacy is too complex and beyond the scope of this page. A simple way to understand is that the adequacy of dialysis is measured in units of Kt/V. Usually an adequate dose of dialysis will be from 1.2 to 1.4. Under certain circumstances this may not alone be taken as a measure of adequacy of dialysis. If a patient's condition requires more or less of dialysis the Nephrologist treating the patient should be able to explain it to the patient adequately. Kt/V is usually measured once per month. It could be seen printed on the copy of the monthly blood tests results all the patients receive.
If the dialysis appears inadequate (low Kt/V) it could be
due to:
1. The dialysis is truly inadequate and the duration of dialysis
need to be increased. Or
2. It could be that the dialysis is inadequate because the vascular
access (AV-Fistula, Catheter, AV-graft) is inadequate to provide
the needed blood flow. Although this could be compensated by
further increasing the duration of the treatment, an appropriate
measure is to evaluate the vessel access and to improve the
blood flow.
3. In rare instances, the large size of the patient might prevent him
in reaching a Kt/V of 1.2 or above. (the V in Kt/V refers to the
volume of the patient.)
If the patient is not receiving adequate dialysis, the ill effects may not appear until several months and even years. Inadequate dialysis also increases the chances of other illnesses in the same patient. Such illnesses also may not be perceived at the time of their occurrence to be due to inadequate dialysis.
Peritoneal Dialysis is a medical procedure used to treat patients with kidney failure
(Uremia). During this procedure sterile fluid called dialysate is infused into the belly
(peritoneal cavity of the abdomen) and is allowed to circulate around the blood vessels.
The dialysate extracts the toxic chemicals from the blood, across the peritoneal membrane
and the wall of the blood vessels. Blood and the dialysate do not mix together or come in
contact with each other. The dialysate with the extracted toxic chemicals is then
discarded and fresh dialysate is infused into the belly again. This process is repeated 4
to 5 times a day, every day (CAPD). When this process is automated (with a machine) almost 5 to 7 such
cycles of filling and draining the belly could be done during the night - while the
patient is asleep (CCPD).
HOW IS PERITONEAL DIALYSIS DONE?
A.
Sterile Peritoneal Dialysate is infused into the abdomen. Once the infusion is complete
the empty bag and the tubing is removed by detaching at the connector. Patient could
go about attending to whatever he wishes. The Dialysate is allowed to 'dwell' in the
abdomen for the next 4 to 6 hours. B. And then by attaching an empty bag at the
connector, the Dialysate with its extracted chemical waste is drained by gravity and
discarded. This cycle will be repeated usually 4 to 5 times a day. This method is called CAPD (Chronic Ambulatory Peritoneal Dialysis). Since this method
takes away a chunk of time during the day, several such exchanges could be done while the
patient is asleep. This involves a cycler, that holds enough Dialysate and intermittently
infuses into the abdomen and periodically drains by opening and closing the clamps
automatically (as programmed). It also warms the fluid to body temperature prior to
infusion. During the daytime patient need not do more than one manual exchange as
described for CAPD. This method of using the cycler during the night is called CCPD (Chronic Cycler-Peritoneal Dialysis)
Either during CAPD or during CCPD, when a predetermined quantity of the dialysate is drained (with the rest is left behind) and new dialysate is added, then it is called TIDAL Peritoneal Dialysis. This method is useful if the patient has a tendency to loose too much body fluid into the dialysate and become dehydrated.
WHAT ARE THE COMPLICATIONS OF PERITONEAL DIALYSIS?
1. Infection through contamination while
connecting and disconnecting:
This causes Peritonitis.
Usually such peritonitis could be treated at
home. Patients are
trained to recognize the onset of peritonitis and
start the initial treatments
at home.
2. Back pain:
The exact reason is not clear. Perhaps it is due to
carrying
2 to 2.5 kg of additional
weight of Peritoneal Dialysate all the time.
Except in a few, this does
not pose a problem.
3. Shoulder pains: Usually this is intermittent and
is usually due to, accidentally,
let air get into the abdomen
at the end of infusion. When the patient sits or
stands the air bubbles raise
to irritate the diaphragm. This causes the pain
referred to the shoulder,
since the nerve supply to the diaphragm and
shoulder are the same.
4. Discomfort due the tip of the catheter inside the
abdomen: As the part of the
catheter that is inside the
abdomen could move freely, sometimes it may touch
the bladder of rectum. This
might cause a sense of urgency to urinate or to
defecate.
5. On occasion, due to the natural and constant
movements of the intestines,
the catheter may get wrapped
up and will not work for several hours.
6. If the patient is unable to carry on the
exchanges without getting peritonitis
often, then such infections
cause the bowels to stick together permanently
(Adhesions) and the
peritoneal dialysis could not be done.
7. Loss of protein through the dialysate:
Unlike hemodialysis, considerable
amount of protein is
extracted from the blood by the peritoneal dialysate.
This is routinely discarded.
Over a period of time this causes protein
malnutrition. Such
patients are likely to experience other adverse outcomes
and frequent infections.
This could be prevented by:
a. Increasing the protein in the diet right from the time peritoneal
dialysis is started
b. Adding protein ( in the form of Aminoacids which are the building
blocks of Protein) to the dialysate before infusing. The aminoacids
are easily absorbed into the blood and are converted to proteins.
Patients with severe liver disease not only loose more protein
through the Peritoneal Dialysis but could also become sick due to
protein infusion through the dialysate (Hepatic Encephalopathy).
8. Dehydration and low blood
pressure due to excessive body fluid removal
through the peritoneal
dialysis.
(CONTD)
