Does propranolol alter the vascular response to phenylephrine before or during halothane anaesthesia in patients with coronary artery disease?

Preoperative beta-adrenergic blockade with propranolol, by allowing unopposed alpha-adrenergic stimulation in response to stress, has been suggested as a factor contributing to hypertension following coronary artery bypass surgery (CABG). Thus, one might expect to find an exaggerated haemodynamic response to phenylephrine (PHE), an alpha 1 agonist. To study this, the cardiovascular response to PHE infusion at 30, 40, and 50 microgram.min-1 prior to and during halothane anaesthesia was measured before surgical stimulation during elective CABG in patients taking chronic propranolol therapy and compared with that of patients not taking any cardiovascular medications. Chronic propranolol therapy did not alter the haemodynamic response to PHE, before or during halothane anaesthesia, and the incidence of postoperative hypertension requiring vasodilator therapy was the same for both groups.