January 10th, 2012

Researchers Find Lower Sweet Spot for Potassium Levels in MI

Current guidelines for the treatment of acute MI recommend that serum potassium be maintained between 4.0 and 5.0 mEq/L, and some believe that the upper limit could be raised to 5.5, but evidence is based on small, outdated studies. Now a study published in JAMA suggests that the ideal potassium range should be adjusted downward.

Abhinav Goyal and colleagues performed a retrospective cohort study of 38,689 MI patients. They found a U-shaped relationship between the postadmission potassium level and in-hospital mortality, with the lowest rate of death found in patients with potassium levels between 3.5 and 4.5.

Postadmission potassium level and mortality rate (adjusted odds ratio):

  • <3.0: 46.2% (8.11)
  • 3.0- <3.5: 11.4% (1.45)
  • 3.5- <4.0: 4.8% (1)
  • 4.0- <4.5: 5.0% (1.25)
  • 4.5- <5.0: 10% (1.96)
  • 5.0- <5.5: 24.8% (3.27)
  • ≥5.5: 61.4% (6.44)

The authors point out that the clinical status of the patient may have been a cause rather than an effect of the potassium level. Since large randomized trials of this topic are unlikely, they recommend that “overly aggressive repletion of potassium levels (which is often automated through the implementation of hospital order sets) may not be advisable in patients with AMI (particularly in those with levels between 3.5 and 3.9 mEq/L), as potassium levels of at least 4.5 mEq/L are associated with harm.”

In an accompanying editorial, Benjamin Scirica and David Morrow acknowledge the limitations of the available data but support the recommendations of the study authors and state that for patients with potassium levels below 3.5, potassium repletion “remains reasonable,” but repletion for levels between 3.5 and 4.0 and target levels greater than 4.5 “do not appear justified.”


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