I am responding to your recent article, “A quality improvement project to enhance the management of hyperkalemia in hospitalized patients” [BCMJ 2012;54:27-33 [9]]. I appreciate the purpose of the article; however, I am alarmed that the authors have not updated the information regarding treatment. The use of cation exchange resins is a myth that continues to be propagated. 

I remember during my own training reading textbooks and being told by senior residents and attending staff physicians how important the use of cation exchange resins were to reduce the overall serum potassium level. This evidence is based on two studies in the NEJM from 1961. These studies are incredibly flawed and would not be worthy of the wastepaper basket within a NEJM office washroom today.

The first by Scherr and colleagues[1] looked at 32 patients with acute or chronic renal failure with hyperkalemia. Twenty to 60 grams of resin plus cathartic was administered as needed. Most patients also received glucose and insulin and some received bicarbonate. All of these patients were placed on low potassium diets and there were no controls. Twenty-three of the 30 patients (two patients were never mentioned again) had a de­crease of 0.4 mEq/L in their serum potassium in the first 24 hours. No statistical analysis was conducted.

The second study[2] had similar distressing issues. Five patients received the resin plus sorbitol, and three pa­tients received sorbitol only. There was once again no placebo control. All of these patients received a carbohydrate-only diet consisting of carob syrup and ginger ale. This was a zero potassium intake diet and their potassium levels were checked 5 days later. 

The first group had a reduction from 6.6 to 5.2 mEq/L in their serum potassium while the second group (sorbitol only) had a reduction from 6.3 to 4.6 mEq/L. No real conclusion can be drawn from this study other than perhaps a zero potassium diet may assist in lowering serum potassium over 5 days.

In 1998 a study was published in the Journal of American Society of Nephrologists entitled “Effect of single dose resin-cathartic therapy on serum potassium concentration in pa­tients with end-stage renal disease.”[3] This study had a sequential study design where different therapies were provided to each end-stage renal disease patient. 

The first stage measured serum potassium after a placebo, then serum potassium was measured at 4, 8, and 12 hours after administering 30 grams of Kaexylate, then again at 4, 8, and 12 hours after 30 grams of Kaexylate with sorbitol. There was no statistical difference in potassium levels between any of the groups at hours 4, 8, and 12.

Perhaps another study needs to be conducted that is more robust and answers this question definitively. I, however, have stopped using cation exchange resins in any form. I simply utilize the other therapies listed in this article and treat the etiology of the hyperkalemia. Most commonly this involves stopping the offending medication. If dilution and promotion of increased potassium excretion will not allow for a return of safe potassium levels, renal dialysis may be required. 

Continued treatment with salbutomol, insulin +/- glucose, bicarbonate if acidotic, fluids and furosemide may need to be tailored to each clinical situation while awaiting dialysis. Cation ex­change resins should not be part of this algorithm unless you find yourself back in 1961. 
—J. Gord McInnes, MD, FRCPC
Kelowna

References

1.    Scherr L, Ogden DA, Mead AW, et al. Management of hyperkalemia with a cation-exchange resin. N Engl J Med. 1961 Jan 19;264:115-119.
2.    Flinn RB, Merrill JP, Welzant WR. Treatment of the oliguric patient with a new sodium-exchange resin and sorbitol; a preliminary report. N Engl J Med 1961 Jan 19;264:111-115.
3.    Gruy-Kapral C, Emmett M, Santa Ana CA, et al. Effect of single dose resin-cathartic therapy on serum potassium concentration in patients with end-stage renal disease. J Am Soc Nephrol 1998;9:1924-1930.