Unable to excrete excess potassium, most dialysis patients must adjust their intake.
At present, almost one fourth of stage 5 CKD patients experience a life-threatening episode of hyperkalemia requiring emergency treatment, according to data cited in a recent article in Seminars in Dialysis (2007;20:431-439).
The authors, Nirupama Putcha, MD, and Michael Allon, MD, note that although “many options have been proposed for the prevention of interdialytic hyperkalemia…prevention currently rests largely upon compliance with diet and a thoughtful use of medication regimens.”
With the loss of the kidneys’ ability to excrete excess dietary potassium, adjusting daily potassium intake is essential for most dialysis patients. The National Kidney Foundation (NKF) Council on Renal Nutrition currently advises limiting potassium to 2-3 g/day for hemodialysis patients, allowing a more liberal intake of 3-4 g/day for people on peritoneal dialysis, and modifying recommendations according to serum potassium levels (Pocket Guide to Nutrition Assessment of the Patient with Chronic Kidney Disease, 3rd ed. 2002).
Though diet is a cornerstone to maintaining safe blood levels of potassium for dialysis patients, “potassium, unlike sodium, cannot be tasted, is seldom listed on nutritional labels, and presents a unique educational challenge,” state Judith Beto, PhD, RD, FADA, and Vinod Bansal, MD (J Am Diet Assoc. 2004;104:404-409).
The NKF Guide to the New Food Label observes that “potassium…may be listed as percent daily values, but it is not required” and cautions that “if potassium and phosphorus are not listed, it does not mean that they are not in that food” (www.kidney.org).
Since the potassium percentage on nutrition facts labels is currently based on the “healthy adult” recommended dietary allowance (RDA) of 3,500 mg/day, the NKF provides a method to assist CKD patients in translating this into useful information for renal diets. It suggests considering foods as “low potassium” if a serving provides less than 3% (less than 100 mg) of the RDA, “medium potassium” if 3%-6% (101-200 mg), “high potassium” if 6%-9% (201-300 mg), and “very high” if more than 9% (more than 300 mg).
Incorporating the NKF potassium recommendations into an easy-to-understand patient education tool for use with CKD patients is demonstrated by Emmye Bermani, MS, and colleagues in Topics in Clinical Nutrition (2008;23:47-55).
The authors designed a low-literacy “potassium pyramid” graphic to serve as the basis for instruction, along with a “potassium fact sheet” addressing safe blood level, common food sources, and medications that may affect potassium. Responses from dietitians surveyed were mostly favorable regarding the project format and literacy level. Though these educational tools still need to be tested with patients, the authors hope their efforts “may offer a new approach for educating patients with CKD on how to follow their prescribed nutrition plan.”
Teaching CKD patients ways to safely include favorite foods on a low potassium diet may help improve quality of life, dietary adherence, and patient outcomes. Recommendations to reduce the potassium content of potato and other tuberous vegetables have typically relied on leaching potassium through soaking.
A more efficient method of reducing the potassium content of these specific types of vegetables, “double cooking,” is described by Jerrilynn Burrowes, PhD, RD, and Nicholas J. Ramer, PhD, in the Journal of Renal Nutrition (2006;16:304-311). The process involves bringing thinly sliced vegetables to a boil, discarding the cooking water, refilling the pot with water, bringing it to a second boil and cooking until done.
Other practical advice to assist patients in improving dietary potassium management as outlined by the NKF includes:
- Limit high-potassium foods (orange, banana, dried fruit, dried peas and beans, lentils, melon, milk, yogurt, molasses, potato, tomato, salt substitute/lite salt containing potassium chloride) and plan meals with assistance from a renal dietitian.
- Look for potassium percentage (if listed on the nutrition facts label) under 6%.
- “Eat a variety of foods but in moderation.”
- Advise patients not to “drink or use the liquid from canned fruits and vegetables, or the juices from cooked meat.”
- Remind patients that almost all foods have some potassium and attention to serving size is key.
- “A large amount of a low-potassium food can turn into a high-potassium food.”
- For dialysis patients, reinforce the importance of receiving treatments as prescribed.