EFFECTS OF DOBUTAMINE AND DOPAMINE ON WHOLE BRAIN BLOOD-FLOW AND METABOLISM IN UNANESTHETIZED MONKEYS

Dobutamine (DO) and dopamine (DA) are positive inotropic agents used clinically to improve cardiac output in patients in acute or chronic heart failure or to counteract intracranial vasospasm. These patients are also at risk for cerebrovascular disease, but studies on the effects of DA on cerebral blood flow (CBF) and metabolism are few and for DO nonexistent. We evaluated the effects on DO and DA on whole brain CBF and cerebral metabolic rates of oxygen (CMRO2) and glucose (CMR(glc)) in unanesthetized rhesus monkeys. Microelectrodes and catheters inserted in the superior sagittal sinus monitored H-2 clearance and sampled cerebral venous blood. Studies were done at low and high doses with control measurements between doses. At 5, 10, and 15 mug/kg/min (n = 6), neither systemic nor cerebral variables were affected by either drug. At doses of 50 and 100 mug/kg/min (n = 4), DO and DA increased arterial blood pressure and heart rate by 15 to 30%. Whereas CBF, CMRO2, and CMR(glc) were clearly unaffected by DO at high doses, they increased by 20-30% with DA, 100 mug/kg/min and although not significant (p > 0.05), the consistency and magnitude of the increase along with the likelihood of a type II error led us to conclude that (a) both DO and DA are less effective in monkeys than in humans and (b) whereas DO at all doses tested showed no indication of affecting CBF and CMR, DA increased CBF and CMR by 20 to 30% at a dose of 100 mug/kg/min.