INCREASING ORGAN BLOOD-FLOW DURING CARDIOPULMONARY BYPASS IN PIGS - COMPARISON OF DOPAMINE AND PERFUSION-PRESSURE

Objective: To determine whether low-dose dopamine infusion (5 mu g/kg/ min) during cardiopulmonary bypass selectively increases perfusion to the kidney, splanchnic organs, and brain at low (45 mm Hg) as well as high (90 mm Hg) perfusion pressures. Design: Randomized crossover tria l. Setting: Animal research laboratory in a university medical center. Subjects: Ten female Yorkshire pigs (weight 29.9 +/- 1.2 kg). Interve ntion: Anesthetized pigs were placed on normothermic cardiopulmonary b ypass at a 100-mL/kg/min flow rate, After baseline measurements, the a nimal was subjected, in random sequence, to 15-min periods of low perf usion pressure (45 mm Hg), low perfusion pressure with dopamine (5 mu g/kg/min), high perfusion pressure (90 mm Hg), and high perfusion pres sure with dopamine. Regional perfusion (radioactive microspheres) was measured in tissue samples (2 to 10 g) from the renal cortex (outer tw o-third and inner one-third segments), stomach, duodenum, jejunum, ile um, colon, pancreas, and cerebral hemispheres. Measurements and Main R esults: Systemic perfusion pressure was altered by adjusting: pump flo w rate (r(2) = .61; p < .05). In the kidney, cortical perfusion pressu re increased from 178 +/- 16 mL/min/100 g at the low perfusion pressur e to 399 +/- 23 mL/min/100 g at the high perfusion pressure (p < .05). Perfusion pressure augmentation increased the ratio of outer/inner re nal cortical blood flow from 0.9 +/- 0.1 to 1.2 +/- 0.1 (p < .05). At each perfusion pressure, low-dose dopamine had no beneficial effect on renal perfusion or flow distribution, Similar results were found in t he splanchnic organs, where regional perfusion was altered by perfusio n pressure but not by dopamine, In contrast, neither changing perfusio n pressure nor adding low-dose dopamine altered blood now to the cereb ral cortex. Conclusions: These data indicate that the lower autoregula tory limits of perfusion to the kidneys and splanchnic organs differ f rom those limits to the brain during normothermic bypass. Selective va sodilation from low-dose dopamine was not found in renal, splanchnic, or cerebral vascular beds, Increasing the perfusion pressure by pump f low, rather than by the addition of low-dose dopamine, enhanced renal and splanchnic but not cerebral blood flows during cardiopulmonary byp ass.