Longstanding conventional wisdom holds that patients hospitalized for heart failure need to maintain a serum potassium above 4.0 mEq/L.
“I’m sure you’ve all written orders to keep the potassium greater than 4.0 mEq/L and the magnesium above 2mEq/L about a million times, like I have,” Dr. Smith said.
But it turns out this traditional practice, which involves a huge cost in terms of time, money, and health care resources, is supported by weak evidence – and an important recent study has now debunked what the investigators termed the potassium “repletion reflex.”
The investigators at the University of Massachusetts identified 4,995 patients admitted with exacerbation of acute heart failure and a normal admission serum potassium level of 3.5-5.0 mEq/L. More than 70% received potassium repletion at least once within a 72-hour observation window, during which 2,080 patients maintained a low-normal serum potassium below 4.0 mEq/L, 2,326 had a mid-normal level of 4.0-4.5 mEq/L, and 589 had a high-normal level of more than 4.5 mEq/L but not more than 5.0 mEq/L.
The study had three endpoints: in-hospital mortality, transfer to the intensive care unit, and hospital length of stay. After statistical adjustment for comorbidities, demographics, and severity at admission, there was no difference between the low- and mid-normal serum potassium groups in any of the three endpoints. In contrast, the high-normal potassium group had a significantly longer length of stay, by a median of 0.6 extra days. The high-normal group also had a 78% increased likelihood of ICU transfer and a 51% increased risk of in-hospital mortality, although neither of these differences reached statistical significance ().
“A potassium greater than 4.5 mEq/L may be associated with increased risk of worse outcomes,” Dr. Smith observed. “I think the sweet spot may be 3.5-4.5 mEq/L based on this study.”
He reported having no financial conflicts regarding his presentation.