In this episode, I’ll discuss the change in serum potassium after supplementation.
A common estimate for the increase in serum potassium levels is 0.1 mEq/L per 10 mEq of potassium administered. However, there is little data that can support this conversion formula. Therefore a group of authors sought to examine the impact of oral and/or Iv potassium supplementation on serum potassium levels and have published their results in AJHP.
The study was a single center retrospective descriptive analysis of 800 patients and their response to potassium supplementation. The median dose of potassium in the study was 40 mEq and this was most often given via the oral route. The authors found that the daily median change in serum potassium level was just 0.05 mEq/L per 10 mEq of potassium administered.
The authors also examined whether several different concomitant medications affected the response to potassium supplementation. Only loop diuretics had a significant effect, reducing the response to 10 mEq of potassium to only 0.03 mEq/L. For patients that were not receiving any medication thought to affect potassium levels, every 10 mEq of potassium administered increased serum levels by 0.07 mEq/L.
The authors concluded:
This study did not support the longstanding rule of thumb for K+ supplementation and found a smaller rise in K+ for every 10 mEq of K+ delivered when looking at patients holistically over a full hospitalized day. Loop diuretics were the drug class identified to have the greatest impact on this metric. Future prospective trials are necessary to provide further guidance on K+ supplementation in the non-ICU hospitalized patient population.
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The study authors may have dropped the ball a bit in the sense of you cannot compare po to iv KCL absorption as the body will absorb more potassium when it is deplete than for levels closer to normal for ex. The IV KCL would have been the one to study….I would be curious to see how close it was for the IV doses…. Lastly this assumes that the K is static and pt is not actively loosing kcl thereby preventing a further drop. Retrospectively they probably could have done a better job selecting the pts no?
Great points Ash! I agree and would love to see more data that is IV-specific and multi-center. This seems like a great research idea for someone with access to a large database. Perhaps they can invert the problem and compare patient characteristics between groups that increase by 0.1 and groups that increase by less than 0.05.