98 Dopamine and Circulation in the Brain: A Study in Newborn Piglets

Abstract

BACKGROUND AND Aims: Dopamine is widely used to treat hypotension in newborns. Data regarding its effect on the circulation in the brain, however, are ambiguous. To test for a direct effect on the brain, we estimated the magnitude of variability in arterial blood pressure (ABP) passing from systemic to cerebral circulation (i.e. frequency gain) during an ABP-challenge with dopamine in piglets. Methods: Piglets (n=7, age 1-2 days) were anaesthetized and monitored with NIRS (cerebral oxygenation) during normo- and hypovolaemia. In both states, ABP was challenged with dopamine during a 20-minute stepwise dose-increment (20, 30, 40 and 50 μg/kg/min). Each infusion lasted 2½ minutes. Pauses lasting 2½ minutes were interpolated. Before and after the dopamine-challenge, ABP was challenged with six inflations of a thoracic aorta balloon. Each inflation lasted 30 seconds and pauses lasting 30 seconds were interpolated. Subsequently, frequency gain between ABP and cerebral oxygenation was calculated (frequency range: 0.003-0.04 Hz). Results: Mean variability in ABP was 36±4.3 mm Hg during balloon challenge and 17±3.2 mm Hg during dopamine challenge (mean ±SEM). Mean gain between ABP and cerebral NIRS was 0.11±0.019 during ABP-challenge with the aorta balloon and 0.12±0.029 μM/mm Hg during ABP-challenge with dopamine (P=0.86). The mean difference was 0.01 [95%-CI: -0.07 to +0.09] Conclusions: ABP-variability induced by dopamine and by inflating an aortic balloon had similar effects on cerebral oxygenation. This suggests that dopamine has no direct constricting or dilating effect on the cerebral blood vessels or that such effects are counterbalanced by changes in cerebral oxygen uptake.