Adequacy of HD

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How frequently should Hemodialysis be done?

The minimum that is advisable is three times a week, each session being four hours long.

When dialysis is done in this fashion, only approximately 10% of kidney functions are replaced ! This amount of dialysis is barely enough to maintain patients symptom-free and away from major problems.

Even better results can be obtained when dialysis is done more frequently and/or longer; e.g. 6 to 8 hrs at night every night. The survival and quality of life in these patients is far better than in those who take dialysis three times a week.

In contrast, people who take dialysis two times a week or less, have poor long term survival, poor quality of life and significantly higher rates of hospitalization for life threatening problems.

What is an adequate Hemodialysis?

Clinical signs of adequate dialysis include:

  • Feeling of well-being
  • Good appetite, good sleep
  • Improved efficiency through the day
  • Good BP control
  • Steady dry-weight (see below) or Increase in dry weight without edema

Dry Weight

This is the lowest body weight at which patient is free of swelling on the feet and has no episodes of low blood pressure or cramps on dialysis.

Weight is recorded before and after each dialysis session. During dialysis, excess water is removed and therefore patient loses weight at the end of dialysis session.

Before the next HD, patient gains weight because he has a certain amount of fluid intake daily. There will obviously be no weight gain if patient passes normal amount of urine daily. This situation is extremely rare in maintenance hemodialysis patients.

How does one measure dialysis adequacy?

There are several ways of doing it. One way is to look for clinical signs as listed above. If all of them are present, the patient is dialyzed adequately.

One can objectively measure dialysis adequacy and this is routinely done at good dialysis centres.

Commonest method is to measure blood Urea level before dialysis and then immediately at the end of that dialysis session. The post-dialysis value should come down by more than 65% of the pre-dialysis value. This is called Urea Reduction Ratio (URR).

E.g. If pre-dialysis Urea is 100 and the post dialysis value is 30, the reduction in urea is by 70%, which means, that particular dialysis session was adequate.

Survival is much longer in patients who are dialyzed adequately i.e. at least three times a week with a URR of 65% each time.

If dialysis is inadequate, how can one improve on it?

If the URR is less than 65%, there are several ways by which this can be improved upon.

  • Increase the blood flow.
    • This will effectively treat more amount of blood in the same time and therefore, clearance will improve.
  • Increase the dialysate flow.
    • This will clean the blood more effectively at the same blood flows.
  • Use a bigger dialyzer.
    • This will provide larger surface area for the exchange process and increase overall efficiency of dialysis.
  • Increase dialysis frequency.
  • Increase duration of dialysis.

What are the complications of Hemodialysis?

Hemodialysis is a very safe therapy. The only common complications are episodes of low blood pressures and cramps. These occur when excess fluid is removed in short span of time.

This is one reason why, between two dialysis sessions, the weight gain should not be high.

Does frequency of hemodialysis reduce with time?

This is a commonly asked question. If you have understood the ‘adequacy of hemodialysis’ section, you already have the answer to that question. No.

The only way to stop dialysis is to get a kidney transplantation done.

Next: Peritoneal Dialysis

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