Hemodialysis

Kidney failure may result from an accident involving a drop in blood pressure, or from a disease of the kidneys. I the former case, recovery is usually spontaneous, but if it takes longer than 2 weeks, the patient may die as a result of potassium imbalance in the blood, which cause heart failure. In the case of kidney disease, the patient can survive with only one kidney, but if both fail the patient’s blood composition has to be regulated by dialysis machine.

A dialysis machine consists of a long cellulose tube coiled in a water bath. The patient’s blood is led from a vein in the arm and pumped through the cellulose (dialysis) tubing. The submicroscopic pores in the dialysis tubing allow small molecules, such as those of salts, glucose, and urea, to leak into the water bath. Blood cells and protein molecules are too large to get through the pores. This stage is similar to the filtration process in the glomerulus.

To prevent a loss of glucose and essential salts from the blood, the liquid in the bath water consists of a solution of salts and sugar of the correct composition, so that only the substances above this concentrationcan diffuse out of the blood into the bathing solution. Thus, urea, acid and excess salts are removed.

The bathing solutionis also kept at body temperature and is constantly changed as the unwanted blood solutes accumulate in it. The blood is then returned to the patients arm veins.


How Hemodialysis Works

In hemodialysis, your blood is allowed to flow, a few ounces at a time, through a special filter that removes wastes and extra fluids. The clean blood is then returned to your body. Removing the harmful wastes and extra salt and fluids helps control your blood pressure and keep the proper balance of chemicals like potassium and sodium in your body.

One of the biggest adjustments you must make when you start hemodialysis treatments is following a strict schedule. Most patients go to a clinic—a dialysis center—three times a week for 3 to 5 or more hours each visit. For example, you may be on a Monday-Wednesday-Friday schedule or a Tuesday-Thursday-Saturday schedule. You may be asked to choose a morning, afternoon, or evening shift, depending on availability and capacity at the dialysis unit. Your dialysis center will explain your options for scheduling regular treatments.

Researchers are exploring whether shorter daily sessions, or longer sessions performed overnight while the patient sleeps, are more effective in removing wastes. Newer dialysis machines make these alternatives more practical with home dialysis. But the Federal Government has not yet established a policy to pay for more than three hemodialysis sessions a week.


Illustration of a dialyzer.
Hemodialysis.

Several centers around the country teach people how to perform their own hemodialysis treatments at home. A family member or friend who will be your helper must also take the training, which usually takes at least 4 to 6 weeks. Home dialysis gives you more flexibility in your dialysis schedule. With home hemodialysis, the time for each session and the number of sessions per week may vary, but you must maintain a regular schedule by giving yourself dialysis treatments as often as you would receive them in a dialysis unit