The haemodynamic effects of propranolol and atenolol medication on dobutamine infusion in patients with coronary artery obstructive disease

We compared the haemodynamic effects of β-blockers on dobutamine infusion in 60 patients undergoing coronary artery bypass graft surgery. All patients had been taking propranolol (n = 30) or atenolol (n = 30) pre-operatively for at least 1 month. After sternotomy, dobutamine was infused at 2 μg/kg per min, and the dose increased to 4 μg/kg per min and then 8 μg/kg per min, at 15-min intervals. In both groups, dobutamine infusion did not increase the cardiac index or the heart rate, but was associated with an increase in mean arterial pressure, systemic vascular resistance index and mean pulmonary arterial pressure in a dose-dependent manner. The haemodynamic responses to dobutamine infusion were similar in the two groups. We conclude that pre-operative medication with β-blockers reduced the inotropic and chronotropic effects of dobutamine infusion. There was no difference between the modification produced by propranolol, a non-selective β-blocker, and that produced by atenolol, a selective β₁-blocker, however.