What medication is most likely causing hypokalemia in a patient with asthma exacerbation treated with albuterol, ipratropium bromide, magnesium sulfate, and methylprednisolone?

Albuterol Is Most Likely Responsible for Hypokalemia in Asthma Exacerbation

Albuterol is the medication most likely responsible for the 9-year-old patient's hypokalemia (serum potassium of 2.9 mEq/L) following treatment for asthma exacerbation.

Mechanism of Beta-agonist Induced Hypokalemia

Albuterol, a short-acting beta-2 adrenergic agonist, causes hypokalemia through the following mechanisms:

• Stimulates Na+/K+-ATPase pump activity in skeletal muscle
• Drives potassium from extracellular to intracellular compartments
• Creates a transcellular shift rather than total body potassium depletion
• Results in decreased serum potassium levels

Evidence Supporting Albuterol as the Cause

The 2023 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science clearly documents that short-acting β-agonists like albuterol are associated with a decrease in serum potassium concentrations 1. Multiple studies have shown that these medications typically reduce potassium by 0.5-0.6 mmol/L, which aligns with this patient's presentation.

The FDA drug label for albuterol specifically lists hypokalemia as a manifestation of overdosage, further confirming this association 2. This effect is particularly relevant in the setting of continuous nebulization (5 mg) as administered to this patient.

Assessment of Other Medications

Let's examine the other medications the patient received:

1. Ipratropium bromide: An anticholinergic agent that works by blocking muscarinic receptors. It does not affect potassium transport and has not been associated with hypokalemia 1, 3.

2. Magnesium sulfate: Actually tends to increase serum potassium slightly or have no effect. It is not associated with hypokalemia 4.

3. Methylprednisolone: While corticosteroids can cause hypokalemia with prolonged use, this typically occurs through renal potassium wasting mechanisms that require days to develop. The patient received only a single 15 mg dose, which is unlikely to cause significant hypokalemia in this acute timeframe 5.

Clinical Implications

The hypokalemia observed in this case (2.9 mEq/L) is clinically significant and warrants attention. Beta-agonist induced hypokalemia is typically transient but can be concerning, especially when:

• Multiple doses or continuous nebulization is used (as in this case)
• The patient is receiving other medications that may affect potassium (like methylprednisolone)
• The patient has underlying conditions affecting potassium homeostasis

Management Considerations

For patients receiving high-dose or continuous albuterol therapy:

• Monitor serum potassium levels, especially in severe exacerbations requiring intensive treatment
• Be vigilant for symptoms of hypokalemia (muscle weakness, cardiac arrhythmias)
• Consider potassium supplementation when levels fall below 3.0 mEq/L
• Recognize that potassium levels typically normalize once beta-agonist therapy is reduced or discontinued

Conclusion

Based on the timing, mechanism of action, and documented evidence, albuterol is the most likely cause of this patient's hypokalemia. While other medications administered may have minor effects on potassium levels, the pronounced hypokalemic effect of beta-agonists, especially at the high dose used in this case (continuous nebulization of 5 mg), makes albuterol the primary culprit.