123 NIMODIPINE ENCHANCES NEWBORN LAMB CEREBRAL BLOOD FLOW

Abstract

Nimodipine (BAY e 9736) a dihydropyridine type Ca²⁺ channel blocker, has been introduced recently as a selective cerebral vasodilator. In this study the effects of Nimodipine on total and regional CBF, selected organ flow and cardiovascular function were investigated in newborn lambs. After anesthesia with 1% chloralose the lambs were intubated and mechanically ventilated. Blood flow to the brain and other organs was measured by radio-actively labeled microspheres injected into the left ventricle. Nimodipine (0.2, 0.6 and 2.0 μg/kg) was administered by bolus intravenous infusion to 5 normotensive animals. At 2.0 μg/ kg the total CBF increased 92.8%. Subsequently, mean arterial blood pressure was decreased in other 6 newborn lambs, from 70.6 to 40.2 mm Hg. Following a 30 μg/kg bolus of Nimodipine, CBF increased significantly above control values (total brain 41.5%, gray matter 53%, subcortex 75.6% and brain stem 68.8%). Nimodipine appears to increase CBF in both the normotensive and hypotensive normoxic newborn lamb without significant side effects in blood pressure, heart rate or arterial blood gases. At the blood pressure chosen for hypotension, autoregulation was preserved and Nimodipine had an additive effect of increasing CBF, presumably by further vasodilatation. These findings suggest that Nimodipine may be of therapeutic value in the hypotensive stressed neonate at risk for ischemic brain injury. However, one must also be concerned about the potential for cerebral hyperfusion and the risk of intracranial hemorrhage in such infants.

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