Q: I know that I have to tell my patients to be careful with dietary potassium when they are taking spironolactone and ACE inhibitors or angiotensin II receptor blockers (ARBs). However, what foods are bad? What is an acceptable K+ level for patients with chronic kidney disease (CKD)?
Potassium (K) is a mineral that aids in the regulation of osmotic pressure and acid–base balance. It is essential for normal excitability of muscle tissue, in particular the cardiac muscle, and it plays a role in the conduction of nerve impulses. A safe serum potassium level for a patient with CKD is 4.0 to 5.0 mmol/L. A serum level between 5.0 and 5.5 mmol/L is considered a caution zone, requiring potassium restriction and laboratory monitoring1 (note: values and ranges vary according to lab). Prescription and OTC medications, herbs, herbals, and dietary intake affect serum potassium.
Medications such as ACE inhibitors and ARBs can cause hyperkalemia by blocking aldosterone production. The Kidney Disease Outcomes Quality Initiative (K/DOQI)2 defines hyperkalemia resulting from ACE inhibitor/ARB use as an increase of serum potassium exceeding 5.0 mmol/L. Therapeutic options to reduce serum potassium include:
•Lowering the dose of the ACE inhibitor or ARB by 50%
•Stopping or reducing other medications that can cause hyperkalemia
•Starting or increasing the dosage of a loop diuretic; or
•Reinforcing dietary restriction.2
Alkali replacement or the use of Kayexalate® (sodium polystyrene sulfonate) may also be used to treat persistent or significant increases in serum potassium.
Diets high in potassium may lead to hyperkalemia in patients with CKD, particularly in patients with a glomerular filtration rate (GFR) below 60 mL/min/1.73 m2. K/DOQI2 recommends 4 g/d of potassium for patients with CKD Stage 1 or Stage 2 and 2 to 4 g/d for patients with CKD Stage 3 or Stage 4. In the latter group, daily recommendations for potassium intake should be based on the individual patient’s serum potassium level.3
Foods containing more than 200 mg of potassium per serving are considered high-potassium foods. Fruits in this designation include avocado, bananas, cantaloupe, honeydew, kiwi, orange, mango, nectarines, bananas, and prunes. High-potassium vegetables include artichokes, dried beans (including baked beans, refried beans, and black beans), broccoli, carrots, canned mushrooms, potatoes (white or sweet), pumpkin, spinach, and tomatoes. Other foods that are high in potassium include bran products, chocolate, milk, molasses, nuts, seeds, peanut butter, salt substitutes, and yogurt.1
Leaching is a helpful way to “pull out” some of the potassium in high-potassium vegetables.4,5 For potatoes, sweet potatoes, or carrots, cut the peeled vegetable into 1/8-inch-thick slices, rinse in warm water, and soak in water 10 times the volume of the vegetables’ volume for a minimum of two hours. Rinse under warm water again, then cook the vegetable in water five times the volume of the vegetables’.
Kristy Washinger, MSN, CRNP, Nephrology Associates of Central Pennsylvania, Camp Hill, PA
REFERENCES
1. Greene JH. Restricting dietary sodium and potassium intake: a dietitian’s perspective. In: Daugirdas JT. Handbook of Chronic Kidney Disease Management. Philadelphia, PA: Lippincott Williams & Wilkins; 2011:81-96.
2. National Kidney Foundation. K/DOQI Clinical Practice Guidelines on Hypertension and Antihypertensive Agents in Chronic Kidney Disease. Guideline 6: Dietary and other therapeutic lifestyle changes in adults. www.kidney .org/professionals/kdoqi/guidelines_bp/guide_6.htm. Accessed November 21, 2012.
3. National Kidney Foundation. K/DOQI Clinical Practice Guidelines on Hypertension and Antihypertensive Agents in Chronic Kidney Disease. Guideline 11: Use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in CKD. www.kidney.org/professionals/kdoqi/guidelines_bp/guide_11 .htm. Accessed November 21, 2012.
4. Nutrition 411. Renal diet preparation in-service for kitchen staff: leaching potassium from vegetables. www.rd411.com/renalcenter/ article1.php?ID=8pro. Accessed November 21, 2012.
5. Burrowes JD, Ramer NJ. Removal of potassium from tuberous root vegetables by leaching. J Ren Nutr. 2006;16(4):304-311.
6. Bargman JM, Skorecki K. Chapter 280. Chronic kidney disease. In: Longo D, Fauci A, Kasper E, et al, eds.
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7. Ryan MJ, Tuttle KR. Elevations in serum creatinine with RAAS blockade: why isn’t it a sign of kidney injury?
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8. Schoolwerth AC, Sica DA, Ballermann BJ, Wilcox CS. Renal considerations in angiotensin converting enzyme inhibitor therapy: a statement for healthcare professionals from the Council on the Kidney in Cardiovascular Disease and the Council for High Blood Pressure Research of the American Heart Association. Circulation. 2001;104(16):1985-1991.
9. Bakris GL, Weir MR. Angiotensin-converting enzyme inhibitor-associated elevations in serum creatinine: Is this a cause for concern? Arch Intern Med. 2000;160(5):685-693.
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