Frequently nebulized beta-agonists for asthma: effects on serum electrolytes

To determine the magnitude of the changes in serum potassium, magnesium, and phosphate during the treatment of acute bronchospasm with repeated doses of beta-adrenergic agonists.

Prospective study of a convenience sample of asthmatic patients.

University teaching hospital emergency department.

Twenty-three patients met the inclusion criteria of age of more than 16 years; a history of asthma or chronic obstructive pulmonary disease; and an acute exacerbation.

Baseline peak expiratory flow rate and serum potassium, magnesium, and phosphate levels were measured. Nebulized albuterol (2.5 mg) was administered every 30 minutes until the patient was discharged from the ED. Before each albuterol treatment, repeat serum levels of potassium, magnesium, and phosphate were determined.

Baseline peak expiratory flow rate averaged 188 +/- 119 L/min. Serum potassium levels decreased significantly (P = .0001 by repeated-measures analysis of variance) from 4.10 +/- 0.468 (baseline) to 3.55 +/- 0.580 mmol/L (90 minutes) and 3.45 +/- 0.683 mmol/L (180 minutes). Potassium decreased to less than 3.0 mmol/L in 22% of patients at some point during the study. Magnesium decreased from 1.64 +/- 0.133 mmol/L (baseline) to 1.48 +/- 0.184 mmol/L (90 minutes) and 1.40 +/- 0.219 mmol/L (180 minutes) (P = .0001). Phosphate levels also decreased, from 3.74 +/- 1.029 (baseline) to 2.84 +/- 0.957 mmol/L (90 minutes) and 2.55 +/- 0.715 mmol/L (180 minutes) (P = .0001).

Aggressive administration of nebulized albuterol during the emergency treatment of acute bronchospasm is associated with statistically significant decreases in serum potassium, magnesium, and phosphate. The mechanism and clinical significance of these findings are unknown and warrant further study.