Hypokalemia in Emergency Medicine

Updated: Apr 05, 2017
  • Author: David Garth, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Overview

Background

Potassium is one of the body's major ions. Nearly 98% of the body's potassium is intracellular. The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential. Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems. [1, 2, 3]

The kidney determines potassium homeostasis, and excess potassium is excreted in the urine.

The reference range for serum potassium level is 3.5-5 mEq/L, with total body potassium stores of approximately 50 mEq/kg (ie, approximately 3500 mEq in a 70-kg person).

Hypokalemia is defined as a potassium level less than 3.5 mEq/L.

Moderate hypokalemia is a serum level of 2.5-3 mEq/L.

Severe hypokalemia is defined as a level less than 2.5 mEq/L.

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Pathophysiology

Hypokalemia may result from conditions as varied as renal or GI losses, inadequate diet, transcellular shift (movement of potassium from serum into cells), and medications.

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Epidemiology

Frequency

United States

As many as 20% of hospitalized patients are hypokalemic; however, hypokalemia is clinically significant in only about 4-5% of these patients. Severe hypokalemia is relatively uncommon.

Up to 14% of outpatients who undergo laboratory testing are found to be mildly hypokalemic.

Approximately 80% of patients who are receiving diuretics become hypokalemic.

International

In an Italian study, Giordano et al found that of 7941 emergency department patients, 13.7% of them had an electrolyte imbalance, with hyponatremia being the most common (44%) and hypokalemia being the next most frequent (39%). The investigators also found that 98% of patients with an electrolyte imbalance had an associated systemic disease. [4]

Sex

Incidence is equal in males and females.

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Prognosis

Hypokalemia usually resolves with appropriate therapy. A study by Krogager et al indicated that patients with hypertension who have a potassium level outside of the 4.1-4.7 mmol/L range, including those who are hypokalemic or hyperkalemic, have an increased mortality risk. For patients with hypokalemia, the 90-day mortality rate was 4.5%, compared with 1.5% for the 4.1-4.7 mmol/L range. [5]

A study by Kieneker et al indicated that not only is hypokalemia linked to the progression of existing chronic kidney disease (CKD), it is also associated with an increased risk of developing CKD, either with or without diuretic use. [6]

A retrospective study by Marill and Miller of emergency department patients indicated that hypokalemia is strongly associated with prolonged heart rate–corrected QT (QTc) duration, particularly in women. The study found that in patients with a potassium level below 3.9 mmol/L, every 1 mmol/L reduction in potassium increased the QTc time by 43.0 ms in women and 29.5 ms in men. [7]

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Patient Education

Diet modification is recommended for those patients who are predisposed to hypokalemia. Increase intake of bananas, tomatoes, oranges, and peaches because they are high in potassium.

For patient education resources, see the Endocrine System Center, as well as Low Potassium.

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