The Role Of Potassium In Dialysis

In the body, the mineral potassium is usually confined to your cells, with relatively small quantities in the blood. When blood potassium concentrations get too high, called hyperkalemia, your heart rate slows. If concentrations are low, called hypokalemia, your heart rate becomes irregular. Both can be fatal. Most individuals with renal failure cannot remove potassium from the blood, so as you eat, the potassium from your food builds up in your blood. Dialysis removes the excess potassium from your blood in the place of your kidneys.

Hemodialysis

Hemodialysis depends on diffusion based on the concentration gradient of potassium between your blood and the dialysate. The dialysate, also called the bath, has a lower concentration of potassium than that of your blood. The potassium therefore flows out of your blood into the dialysate, following the concentration gradient, going from high concentration in the blood to the lower concentration in the dialysate.

Gradual Removal is Best

Using diffusion to remove potassium from the blood can lead to more being removed in the first half of a dialysis session than the last half, when the serum concentration is lower. A study published in "Contributions to Nephrology" in 2005 showed that patients who suffer from irregular heart beats, or arrhythmias, benefited more from dialysis where the potassium gradient changed to allow a constant removal rate. This approach spread the potassium removal evenly throughout the session. The researchers concluded that the rate of potassium removal was also important, not just the removal itself.

Maintenance Hemodialysis

Your health care team will work with you to develop a dialysis plan to control your serum potassium levels. A 3-year study of 81,013 hemodialysis patients from the DaVita Clinics throughout the U.S. was reported in the "Clinical Journal of the American Society of Nephrology" in 2007. Patients with serum potassium concentration between 4.6 and 5.3 mEq/L before dialysis were more likely to survive. Mortality rate increased with predialysis potassium levels below 4 mEq/L or above 5.6 mEq/L.

Your Potassium Intake

The main function of dialysis is to help you get your serum potassium levels in an acceptable range. Since your diet will play a significant role in the amount of potassium that will accumulate in your blood between dialysis sessions, you can help to control your levels by choosing foods with lower potassium content. Pasta, bread, American cheese, grapes, blueberries, corn and olives all give less than 100 mg of potassium per serving. On the other hand, bananas, nectarines, prunes, honeydew melon, celery, carrots, potatoes, chicken, fish and nuts have at least 300 mg of potassium per serving.