Effects of salbutamol given by metered-dose inhaler on dispersion of ventricular repolarization.

Objective: Salbutamol has previously been shown to increase the QT dispersion (QTd), which may be associated with high risk of cardiac arrhythmia in asthmatics. Cardiac effects of salbutamol occur in dose-related manner and salbutamol dose given by metered-dose inhaler (MDI) during acute asthma attack is commonly lower than the dose given by nebulizer. This prospective cohort study aimed to assess the effect of salbutamol given by MDI on QTd in the course of moderate acute asthma attack.

Methods: Thirty-two children, between 5-15 years of age, who were able to perform spirometric maneuvers and salbutamol administration by MDI through the spacer, were enrolled. Salbutamol was administered at a dose of 50 µg/kg three times at 15-20 minute intervals. Clinical features, spirometric parameters and QT measurements from the standard electrocardiograms were studied at baseline and 15 minute after the third inhalation of salbutamol. The relation between the continuous variables was evaluated by using paired Student's t-test.

Results: Overall, treatments were well-tolerated, significant improvement of pulmonary index scores and spirometric parameters were observed after treatment. No significant difference was observed between the pre and post-treatment values in QTd (30.4±5.6 ms; 33.7±6.2 ms, p=0.086) and corrected QTd (38.8±6.4 ms; 40.7±7.7 ms, p=0.18).

Conclusion: Salbutamol administered using metered dose inhaler showed satisfying clinical improvement with notably lower doses than the dose given by nebulizer and does not affect ventricular repolarization in children with moderate acute asthmatic attack.