Hypokalaemic and electrocardiographic effects of aminophylline and salbutamol in obstructive airways disease.

The hypokalaemic and electrocardiographic effects of nebulised salbutamol (2.35 mg x 2, 120 min apart) and intravenous aminophylline (6 mg/kg followed by 0.5 mg/kg/hr infusion) alone and in combination, were investigated in eight patients with stable asthma. Both agents produced significant hypokalaemia, mean maximum for salbutamol 0.55 mmol/l, mean maximum for aminophylline 0.29 mmol/l. Salbutamol increased the QTc interval and depressed T-wave amplitude whilst aminophylline decreased PR interval. These effects were increased when they were given in combination but were highly variable between individuals. It is likely that arrhythmias may be precipitated in patients with hypoxaemia, acidosis or those with preexisting cardiovascular disease.