Blood Flow Distribution and Brain Metabolism during Tolazoline-Induced Hypotension in Newborn Dogs

Abstract

Tolazoline is used in neonatal intensive care to treat hypoxia secondary to persistent pulmonary hypertension of the newborn. Its use is often complicated by systemic hypotension. We compared the effect of tolazoline-induced hypotension on organ blood flow, regional brain blood flow, and cerebral metabolism in hypoxic newborn dogs whose mean arterial pressure fell by more than 20% with a second group whose blood pressure fell by less than 20%. Blood flows were measured by the radioactive microsphere technique. We found no changes in organ blood flow, regional brain blood flow, and cerebral metabolism in hypoxic animals whose mean arterial blood pressure decreased less than 20% during tolazoline administration. However, in those animals whose mean arterial blood pressure decreased more than 20%, we found a decrease in cerebral blood flow. As a consequence of decreased cerebral blood flow, cerebral oxygen delivery decreased. However, oxygen extraction increased so that cerebral metabolic rate was preserved.