How to keep rectal Kayexalate (polystyrene sulfonate) in place?

Retaining Rectal Kayexalate: Practical Techniques

The most effective method to retain rectal Kayexalate is to insert a soft, large-bore (French 28) rubber catheter approximately 20 cm into the rectum with the tip positioned in the sigmoid colon, tape it securely in place, administer the suspension by gravity while keeping particles suspended by stirring, flush with 50-100 mL of fluid, clamp the tube, and leave it in place for several hours—elevating the hips on pillows or adopting a knee-chest position if back leakage occurs. 1

Optimal Administration Technique

Catheter Placement and Positioning

• Use a soft, large-bore rubber tube (French 28) inserted 20 cm into the rectum to position the tip well into the sigmoid colon, then tape it securely in place 1
• This deeper placement prevents the resin from depositing in the rectal ampulla where exchange surface area is greatly reduced and effectiveness is minimal 1

Suspension Preparation and Delivery

• Prepare the suspension fresh (do not store beyond 24 hours) using 30-50 g of Kayexalate in 100 mL of aqueous vehicle warmed to body temperature 1
• Agitate gently during administration to keep particles in suspension—avoid creating a paste consistency as this dramatically reduces the exchange surface area 1
• Introduce the suspension by gravity while continuously stirring to maintain particle suspension 1
• Flush the catheter with 50-100 mL of fluid after administration, then clamp and leave in place 1

Retention Strategies

• Target retention time of several hours (ideally as long as possible) to maximize potassium exchange 1
• If back leakage occurs, elevate the hips on pillows or have the patient adopt a knee-chest position temporarily 1
• Consider using a somewhat thicker suspension (but never a paste) to reduce leakage, though this must be balanced against maintaining adequate exchange surface 1

Critical Safety Considerations

Pre-Administration Assessment

• Perform a cleansing enema before Kayexalate administration to clear the rectum and sigmoid colon 1
• Rule out contraindications including neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 2, 3

Post-Administration Irrigation

• After retention period, irrigate the colon with non-sodium containing solution at body temperature to remove the resin 1
• Use approximately two quarts of flushing solution, draining returns constantly through a Y-tube connection 1
• This step is critical as retained Kayexalate crystals can cause severe gastrointestinal injury 4, 5, 6

Common Pitfalls to Avoid

Formulation Errors

• Never heat the suspension as this alters the exchange properties of the resin 1
• Avoid sorbitol-containing preparations, particularly in neonates and high-risk patients, as sorbitol increases the risk of intestinal hemorrhage and necrosis 2, 4, 5
• Hospital pharmacies should prepare sorbitol-free formulations when needed 2

Administration Mistakes

• Do not allow paste formation—this creates a mass with minimal exchange surface that is particularly ineffective if deposited in the rectal ampulla 1
• Do not administer without securing the catheter—unsecured tubes lead to immediate expulsion and treatment failure 1
• Do not skip the post-retention irrigation—failure to remove resin crystals is associated with colonic necrosis, transmural injury, and mortality rates up to 33% 4, 6

High-Risk Populations

• Extremely preterm neonates may develop intestinal hemorrhage (hematochezia) from rectal Kayexalate and require particularly careful monitoring 2
• Uremic patients are at substantially higher risk for gastrointestinal necrosis, with the colon being the most common site of injury (76% of cases) and transmural necrosis occurring in 62% of adverse events 4, 5
• Patients with recent ischemic colitis or bowel injury are at risk for rectal stenosis from foreign body reaction to SPS crystals 7

Monitoring and Follow-Up

• Observe for signs of gastrointestinal injury including abdominal pain, rectal bleeding, or signs of perforation, particularly in the first 19.8 days of therapy (average time to adverse events) 6
• Consider alternative therapies (newer potassium binders like patiromer or sodium zirconium cyclosilicate) in patients at high risk for gastrointestinal complications 4
• The colon is the most frequently affected site (76.3% of cases), with drug crystals histopathologically proven in 95.5% of adverse events 6