Interactions of adrenergic beta-receptor blockade (oxprenolol) and PCO2 in the anaesthetized dog: influence of intrinsic beta-sympathomimetic activity.

Effects of change in PaCO2 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 tension.