Albuterol, levalbuterol and tachycardia

Motivation:  In the ICU and inpatient setting, tachycardia is a common vital sign abnormality that has many different root causes. One of the measures taken in attempt to decrease heart rate is to limit beta-agonists such as inhaled or nebulized albuterol, a common medication used for the shortness of breath or wheezing experienced by many patients. One solution that has been suggested to me was to use levalbuterol instead of albuterol...Physiologically it makes sense that albuterol or levalbuterol would increase heart rate, but I was not sure about any physiological/molecular reason why levalbuterol would be associated with less tachycardic side effects, and was also concerned about levalbuterol's higher cost. So does albuterol really contribute to increased tachycardia, and would levalbuterol be a better option?

Study:  Khorfan FM, Smith P, Watt S, Barber KR. Effects of nebulized bronchodilator therapy on heart rate and arrhythmias in critically ill adult patients. Chest. 2011 Dec;140(6):1466-72.

Methods: This was a 2:1 randomized, prospective, single-blind crossover study in 70 adult ICU patients who were randomized to alternating 4-6 hour courses of nebulized albuterol (2.5 mg) or levalbuterol, along with ipratropium. Group A received 0.63 mg, while Group B received 1.25 mg of levalbeterol. Cardiac monitoring was performed to measure heart rate and rhythm before, during and after treatment.

Results: The 70 patients consisted of almost equal numbers of men and women, with age ranges from 35-92, and slightly more than half on mechanical ventilation. Multisystem organ problems were common in this population. The median number of treatments per patient was 23, ranging from 1 to 45. There was no significant difference in change in heart rate after albuterol (0.89 ± 4.5 bpm) or levalbuterol (0.85 ± 5.3 bpm) treatment in Group A. In Group B, levalbuterol actually was associated with faster heart rate (increase of 1.4 ± 5.4 bpm) compared to albuterol (decrease of 0.16 ± 5.1 bpm) (p=0.03); but when analyzing for measures that were taken >= 5 hours apart, this difference was no long statistically significant. There was only one patient who had to be discontinued on treatment, after experience a 5 beat run of NSVT after 6x albuterol treatment.

Discussion: As for levalbuterol, its substitution for albuterol was not justified in this study - in fact, in Group B, in which a higher levalbuterol dose was used, post-therapy heart rate was actually faster than post-albuterol heart rate. Unexpectedly, from this study, it seemed that albuterol or levalbuterol did not significantly worsen tachycardia, even in this very sick population of patients. This is useful - and comforting - to know for patients who are tachycardic, but also have wheezes or increased airway resistance who would benefit from temporary courses of nebulized beta-agonists. One limitation of the applicability of this study is the fact that heart rate comparisons were made only after a limited number of treatments per patient, so it could be possible that over longer term and more treatments +/- higher frequency +/- higher dosing, there would be significantly increased heart rate. So in a patient receiving longer term albuterol therapy, I would still consider tapering down or decreasing albuterol therapy if tachycardia were a problem, since this would make sense physiologically.