Pilot study to compare the bronchodilator and metabolic responses to terbutaline infusion in seven asthmatic subjects : are they correlated ?

SUMMARY We compared the changes in peak expiratory flow rate (PEFR), plasma potassium and plasma glucose during and after an infusion of the β2-agonist, terbutaline, in seven asthmatic subjects. Our aim was to establish whether these metabolic parameters could be correlated with PEFR. The percentage changes in PEFR were significantly correlated with the percentage changes in glucose (r = 0.60, P<0.001) and potassium (r = −0.64, P<0.001). Values for glucose and potassium changes were also correlated significantly with each other (r = 0.86, P<0.001). This suggests that in asthmatic subjects on β2-agonist treatment, plasma potassium could be used as a surrogate marker for β2 activity at bronchi. It also implies that the most effective β2-agonist bronchodilators will produce the greatest fall in plasma potassium. Further studies with a larger number of patients are needed to confirm this.