Effect of nimodipine on cerebral and organ blood flow in normal and posthypoxemic newborn piglets.

Using the isotope-labelled microsphere method, blood flow to the brain, the heart and the kidneys were studied in newborn piglets during nimodipine infusion. Twenty piglets were studied in two different groups. Group 1 (n = 8) was kept normoxic and given a continuous nimodipine infusion (15 micrograms/kg/min). Group 2 (n = 12) was made hypoxemic by breathing 10% O2 for 10 min followed by an identical nimodipine infusion as group 1. In spite of a significant systemic hypotension, nimodipine infusion alone significantly increased blood flow in the brain stem and right cardiac ventricle at 30-60 min of infusion, while blood flow to cerebellum, cerebrum and the left cardiac ventricle did not change. Blood flow to the kidneys decreased significantly. In posthypoxemic piglets nimodipine infusion gave almost similar flow patterns, however, the changes appeared at an earlier time. We conclude that in spite of a significant reduction in blood pressure, cerebral and cardiac blood flow is preserved both in normal and posthypoxemic animals even at high doses of nimodipine. However, because of the decreased blood flow to the kidneys further dose-response studies are needed before clinical use in asphyctic newborns.