How can I remove potassium from a toddler's supplemental formula using sodium polystyrene sulfonate (Kayexalate)?

How to Decant Potassium from Toddler Formula Using Kayexalate

When oral or rectal administration of sodium polystyrene sulfonate (Kayexalate/SPS) is not feasible or desirable in a hyperkalemic toddler, pretreating the supplemental formula with SPS can safely reduce potassium content by 12% to 78%, depending on the dose used. 1

Practical Protocol for Formula Pretreatment

Optimal Dosing and Preparation

• Add 1 gram of SPS per mEq of potassium in the formula as the standard starting dose. 1
• Mix the SPS thoroughly with the prepared formula to create a slurry, then allow it to settle for 50 minutes to 1 hour—contact time beyond 1 hour does not significantly improve potassium removal. 2, 3
• After settling, carefully decant the supernatant (the liquid portion) and discard the resin sediment at the bottom. 2, 3
• The decanted formula is now ready for feeding through bottle or enteral tube. 1

Dose-Response Relationship

• Using 0.5 g SPS per mEq of potassium reduces potassium by approximately 25%, while 1.0 g per mEq achieves 36% reduction. 4, 3
• Adding more than 20 mL (approximately 16-20 grams) of SPS reaches a plateau effect with no additional potassium removal benefit. 3
• The KDOQI guidelines note that depending on dosage, potassium reduction ranges from 12% to 78%. 1

Critical Safety Considerations

Sodium Load Warning

• Each gram of SPS delivers approximately 100 mg (4.1 mEq) of sodium, which exchanges for the removed potassium. 5, 4
• Pretreating formula with 1.0 g SPS per mEq of potassium causes a 324% increase in sodium content of the final product. 4
• This massive sodium load can cause serious hypernatremia, particularly in extremely low birth weight infants (<1000 g), where each 15 g dose delivers roughly 1500 mg of sodium. 6
• Monitor serum sodium, potassium, calcium, and magnesium levels closely during treatment, as SPS is non-selective and also binds calcium and magnesium. 6, 7, 5

Avoid Sorbitol-Containing Products

• Never use commercially available liquid SPS preparations that contain sorbitol for formula pretreatment, especially in infants and toddlers. 6
• Sorbitol is hyperosmolar and can cause intestinal hemorrhage (hematochezia), intestinal necrosis, and perforation, with mortality rates of approximately 33% among affected pediatric patients. 6, 7
• Hospital pharmacies must prepare sorbitol-free SPS formulations for pediatric use. 6

Gastrointestinal Complications

• Serious GI adverse events including intestinal necrosis, perforation, ischemic colitis, and bleeding have been reported with SPS use. 6, 7, 5
• This method may be particularly indicated when there are concerns about enteral feeding tube obstruction from direct SPS administration. 1

Nutritional Impact and Monitoring

Changes in Mineral Content

• Beyond sodium increases, pretreatment causes slight increases in phosphorus, iron, and zinc, with no significant change in magnesium content. 4
• Calcium content may increase by 1.6-fold when using calcium polystyrene sulfonate instead of sodium polystyrene sulfonate. 2
• The KDOQI guidelines note that other nutrients such as sodium and calcium may increase or decrease with binder use. 1

Formula Selection Considerations

• Standard cow's milk-based infant formulas contain 700-740 mg/L (18-19 mmol/L) of potassium, while breast milk has lower content at 546 mg/L (14 mmol/L). 1
• Volumes of formula ≥165 mL/kg will exceed 120 mg (3 mmol) K/kg and may aggravate hyperkalemia in toddlers with chronic kidney disease. 1
• For toddlers with milk allergy requiring hydrolyzed formulas, pretreatment with SPS can successfully maintain adequate serum potassium levels while ensuring appropriate weight gain. 8

Alternative Potassium Reduction Strategies

Preparation with Deionized Water

• Preparing powdered formula with deionized water instead of tap water reduces potassium by 30% compared to ready-to-feed formulas. 2
• This method is more practical and convenient than SPS pretreatment for mild potassium restriction needs. 2

When to Use This Method

• Formula pretreatment is indicated when oral, enteral, or rectal administration of SPS is ineffective, undesirable, or not feasible. 1
• This approach is appropriate for moderate to severe hyperkalemia requiring potassium binder treatment. 1
• Do not rely on this method for emergency hyperkalemia—SPS has a variable and delayed onset (several hours to days) making it unsuitable for life-threatening situations. 6, 7

Common Pitfalls to Avoid

• Never use this as sole therapy for acute, life-threatening hyperkalemia (K+ >6.5 mEq/L or ECG changes)—use IV calcium gluconate, insulin with glucose, and sodium bicarbonate first. 6, 7
• Do not use sorbitol-containing SPS products for formula pretreatment due to severe GI complication risk. 6, 5
• Monitor for sodium overload in toddlers with heart conditions, hypertension, or volume-sensitive states given the massive sodium exchange. 7, 4
• Check electrolytes frequently including potassium, sodium, calcium, and magnesium to detect hypocalcemia and hypomagnesemia. 6, 7, 5
• Consider newer potassium binders (patiromer, sodium zirconium cyclosilicate) for chronic management, as they have superior safety profiles compared to SPS. 6, 7