INTERACTIONS OF ADRENERGIC BETA-RECEPTOR BLOCKADE (OXPRENOLOL) AND P co 2 IN THE ANAESTHETIZED DOG: INFLUENCE OF INTRINSIC BETA-SYMPATHOMIMETIC ACTIVITY

Abstract

Effects of change in Pa_co2 on systemic and coronary haemodynamics and on coronary sinus blood-gases have been studied in 10 open-chested dogs in which the lungs were ventilated with 0.8% halothane in oxygen, before and after administration of oxprenolol 0.3 mg kg⁻¹ i.v. The hyperdynamic response of the circulation to hypercapnia was only marginally reduced after oxprenolol (cardiac output increased by 10% as opposed to 16% before oxprenolol). Before and after oxprenolol, hypocapnia caused large reductions of coronary blood flow (−24% and −20% respectively), while hypercapnia caused large increases of coronary blood flow (+59% and +34% respectively). Oxprenolol does not appear to modify significantly the circulatory response to arterial carbon dioxide tension.