Nurse Erica is planning to administer a sodium polystyrene sulfonate (Kayexalate) enema to a client with a potassium level of 5.9 mEq/L. Correct administration and the effects of this enema would include having the client:
A. Retain the enema for 30 minutes to allow for sodium exchange; afterward, the client should have diarrhea.
B. Retain the enema for 30 minutes to allow for glucose exchange; afterward, the client should have diarrhea.
C. Retain the enema for 60 minutes to allow for sodium exchange; diarrhea isn’t necessary to reduce the potassium level.
D. Retain the enema for 60 minutes to allow for glucose exchange; diarrhea isn’t necessary to reduce the potassium level.
Correct Answer: A. Retain the enema for 30 minutes to allow for sodium exchange; afterward, the client should have diarrhea.
Kayexalate is a sodium exchange resin. Thus the client will gain sodium as potassium is lost in the bowel. For the exchange to occur, Kayexalate must be in contact with the bowel for at least 30 minutes. Sorbitol in the Kayexalate enema causes diarrhea, which increases potassium loss and decreases the potential for Kayexalate retention.
Option B: Sodium polystyrene sulfonate (SPS) is an insoluble polymer cation-exchange resin. After ingestion of oral formulation or application through the rectal route, this resin exchanges sodium with potassium ions from the intestinal cells. Then the potassium binds with SPS, continues to move through the gastrointestinal tract, and is finally eliminated in the feces.
Option C: But sodium polystyrene sulfonate is not selective for potassium; it may bind with calcium and magnesium. This drug begins its action within 2 to 24 hrs of its administration and continues its work up to 4 to 6 hours before it gets eliminated from the body through feces. The exchange capacity of SPS is approximately 33% or 1 mEq of potassium per 1 gram of resin, and this number is not constant. It may be as low as 0.4 to 0.8 mEq/gram of SPS resin.
Option D: After administration, SPS should be retained in the colon for at least 30 to 60 min. After completing retention, to remove remaining resin, irrigation should be done with non-sodium colonic irrigant. In the past, SPS used to be coadministered with sorbitol to reduce the chance of constipation, but in 2009, the FDA issued a warning against the concomitant use of SPS and sorbitol, due to occurrence of colonic necrosis and other serious GI side effects.
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