The origins of the myth
Why the myth is wrong
thought often cited as a cause of hyperkalemia in those with renal dysfunction, infusion of LR with approximately 4 mEq/L potassium should not cause hyperkalemia. Even if the entirety of such a patient’s plasma space was replaced with LR, the K+ concentration would not exceed the concentration of potassium in LR (4 mEq/L).
Secondly, when one considers that the volume of distribution of potassium is greater than the extracellular fluid volume, it becomes clear that any infusion with a near-normal potassium concentration will have almost no effect on the serum potassium level. Consider, for example, a 70-kg man with a serum potassium concentration of 6 mEq/L and an extracellular fluid volume of 15 liters. Let’s suppose that we infuse him with one liter of a solution containing 8 mEq/L potassium. His final serum potassium concentration will be a weighted average of 6 mEq/L multiplied by 15 liters and 8 mEq/L multiplied by 1 liter, which comes out to be 6.1 mEq/L. Thus, his potassium level only increases by 0.1 mEq/L, a barely measurable difference. Considering that potassium equilibrates between the intracellular and extracellular fluid spaces, its volume of distribution is much higher than the extracellular fluid volume and therefore the increase in potassium will be lower than 0.1 mEq/L (Huggins 1950; Winkler 1938). Therefore, although a fluid with twicethe potassium concentration of LR (8 mEq/L) could theoretically increase the serum potassium level, it would require a vast amount of such fluid to have any significant effect.
What about Plasmalyte or Normosol?
- Thanks to @nfkb, this post has been translated into French (please see his blog here). Greatly appreciated @nfkb! All efforts to expunge this myth are needed.
- Skeptical Scalpel (@Skepticscalpel) feels that social media deserves recognition by academia, and used this blog post as an example. See his comment and my response also below.
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