Effect of low dose adrenaline and noradrenaline infusions on airway calibre in asthmatic patients

Airway, cardiovascular and metabolic responses were measured in six asthmatic patients with stable asthma during separate adrenaline, noradrenaline and control infusions. Four incremental infusion rates (4, 10, 25 and 62.5 ng min-1 kg-1) produced circulating catecholamine concentrations within the physiological range. Specific airways conductance and maximal expiratory flow rates measured from complete and partial flow-volume curves increased significantly (P less than 0.05) during adrenaline infusion, in a dose-response manner. No changes in specific airways conductance or maximal expiratory flow rates were seen during the noradrenaline or control infusion. The highest adrenaline infusion rate caused a rise in systolic blood pressure (P less than 0.05) and plasma glucose (P less than 0.05) and a fall in plasma potassium (P less than 0.05). Noradrenaline infusion caused a slight increase in diastolic blood pressure (P less than 0.05) but no metabolic changes. No cardiovascular or metabolic changes occurred during the control infusion. Infused adrenaline, producing circulating concentrations within the physiological range, caused dose-related bronchodilatation in asthmatic patients. Circulating noradrenaline does not appear to have a role in the control of basal airway tone in asthmatic patients.