Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background: Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO). Methods: General hemodynamics and regional blood flows assessed by microsphere technique (15 mu m) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H2O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg.kg(-1) followed by 0.15 mg.kg(-1).h(-1), n=8) or verapamil (0.1 mg.kg(-1) followed by 0.3 mg.kg(-1).h(-1), n=8). Results: CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow Similar patterns were seen during SE and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects Of verapamil were less evident but myocardial perfusion tended to increase. Conclusions: The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.