Hemodialysis literally means dialysis of the blood, removing toxic solutes
in the blood that would normally be eliminated by the healthy kidney. It
is one of two types of dialysis. A patient with end-stage renal failure
can receive hemodialysis therapy in a clinic or hospital. Four hours three
times a week, the patient is connected to a dialysis machine. Blood, attained
through AV access in the form of a double-lumen catheter, AV fistula, or
AV graft, is then pumped from the patient to a filter. This filter then
eliminates specific toxicities of the blood. Blood, now with healthy concentrations
of these solutes, is returned to the patient.
How it Works
The hemodialysis filter (picture) consists of a semipermeable membrane which separates the patients blood from a solution called dialysate. Dialysate contains electrolyte and other necessary solute concentrations so that the patient maintains healthy levels of these elements in their body. Thus, by way of diffusion, in which higher concentrations equilibrate with lower concentrations, toxins such as creatinine, urea, etc. flow from the patient's blood to the dialysate. (SCHEMATIC OF HEMO)
Types of Blood Access
The three types of blood access are:
A double lumen cather is usually used in emergencies, though it may be used for long term access as well. Disadvantages are the formation of blood clots, infections, and can inhibit the success of an AV fistula or graft later on.
An AV graft, is usually a teflon tube that connects the artery and vein. It must be allowed to mature (that is, for the walls of the vessels to becomes thicker) for approximately two weeks. Disadvantages include time for maturity as well as stenosis (narrowing of the blood vessels) of the outflow path (because of increased venous pressure).
An AV fistula also connects the artery and vein. However, a couple of months rather than weeks must pass for the blood vessels to mature. Advantages of the fistula include longer survival rate (1.5 years more than the graft), decreased stenosis and infection.
Issues of Hemodialysis
The disadvantages of hemodialysis deal with personal freedom. The patient,
expected to go to a clinic three times a week, follows a strict schedule,
often using additional time being transported to a clinic, waiting for
one's turn, etc. Another major disadvantage is the health risk associated
with access. Often, patients develop infections at blood access sites.
Peritoneal Dialysis is the second type of dialysis available to those with chronic renal disease. Also known as CAPD, or Continous Ambulatory Peritoneal Dialysis, the patient's peritoneal membrane acts as a filter. Dialysis fluid is drained into the peritoneal cavity (twenty minutes), kept in the patient for four hours, and then drained (twenty minutes). Access is maintained through a catheter that runs from the patient's abdomen; because this can easily be infected, the patient must take cleaning precautions when conducting the dialysis, or exposing the access site. The advantages of CAPD is the freedom attained from self-dialysis. Disadvantages include peritonitous and other inflamations of the peritoneal, and actual membrane failure.
Hemodialysis and Peritoneal Dialysis
In a study done by Majkowicz M. et al in the International Journal
of Artificial Organs, the quality of life of peritoneal dialysis patients
was compared to hemodialysis patients. The research revealed a "significant
difference in symptoms" in Hemodialysis patients compared with controls.
The latter complained often about pain, experiencing nausea, anorexia,
and sleep disturbances. On the other hand, peritoneal patients were more
similar to controls, noteably differing in the "higher intensity" of symptoms
due to gastrointestinal problems. These patients also complained more about
loss of appetite compared to hemodialysis patients. Thus, although the
quality of life for peritoneal dialysis patients is comparatively better
than hemodialysis patients, the former treatment is not always available
to all patients (ex: diabetics who cannot handle glucose levels in the