Effects of diadenosine tetraphosphate on systemic and regional hemodynamics in dogs

Diadenosine tetraphosphate (AP(4)A) produces vasodilation and hypotension. If AP(4)A is to be employed clinically, its influence on systemic and regional hemodynamics needs to be investigated. In this study, we observed systemic and regional hemodynamics during reduction of mean arterial pressure (MAP) induced by AP(4)A in dogs.

Nineteen mongrel dogs were allocated to three groups: those given physiological saline (vehicle group) and dogs in which MAP was decreased either by 8% (8% group) or by 30% (30% group) by infusion of AP(4)A. Systemic hemodynamics and microsphere-determined regional blood flow to vital organs were assessed before and during AP(4)A infusion.

In the 8% group, cardiac output (CO) increased, and systemic vascular resistance (SVR) decreased during AP(4)A infusion. Although regional blood flow to myocardium and portal organs increased, hepatic blood flow decreased. In the 30% group, heart rate and SVR decreased, and stroke volume index increased without change in CO. Regional blood flow to myocardium, kidneys, and portal organs increased. In both groups, cerebral blood flow remained unchanged.

During the decrease in MAP induced by AP(4)A, there were increases in regional blood flow distributed to the myocardium, kidneys, and portal organs, without change in the blood supply to the brain. This finding suggests that AP(4)A may be clinically useful for reducing blood pressure without compromising blood flow to vital organs.