Hypokalemia induced by inhaled bronchodilators.

Since parenteral beta 2-adrenergic stimulation can induce hypokalemia, we postulated that administration of beta 2 adrenoreceptor agonists by inhalation could induce the same. We administered the usual clinical doses of three commonly used bronchodilators to each of six subjects receiving assisted mechanical ventilation in line with the ventilator: two beta 2-adrenoreceptor agonists, metaproterenol, 5 percent solution, and isoetharine, 1 percent solution; and the anticholinergic agent atropine as a control. Each bronchodilator was nebulized over 10 to 15 minutes in random order, four hours apart, and given to every subject. Plasma potassium was measured at five-minute intervals and arterial blood gases at 15-minute intervals, for a total of 50 minutes after administration of each bronchodilator. Following administration of each drug, plasma potassium showed an average decline. The mean decline in plasma potassium from baseline was statistically significant for metaproterenol (p = 0.04) and atropine (p = 0.001) but not for isoetharine (p = 0.09). Although there were no statistically significant differences among the declines in plasma potassium induced by the three drugs, metaproterenol caused the greatest decline (-0.6 mEq/L).