1585 AUTOREGULATION OF BRAIN BLOOD FLOW (BBF): REGIONAL DIFFERENCES IN REDUCED BBP WITH HYPOTENSION


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The potential use of a piglet as a model for investigation of brain blood flow (BBF) was evaluated by assessing the presence of autoregulation in 11 spontaneously breathing newborn piglets.


MABP was altered by phlebotomy. Within the normotensive range (MABP=51-105 mmHg) no significant change in BBF (measured by the microsphere technique)occurred (r=0.03) indicating the presence


of autoregulation. During hypotension (MABP=15-50 mmHg), a pressure passive relation exists between BBF and MABP (r=0.59). However, since the piglets breathed spontaneously and


hyperventilated during hypotension, both the MABP and PaCO2 fell and both correlated with BBF during hypotension. Thus, it is uncertain which factor is responsible for the loss of


autoregulation. The blood flow (BF) to three specific regions of the brain (cerebrum, cerebellum, brainstem) and MABP also showed no correlation during normotension. During hypotension each


region demonstrates significant pressure passive relationships, but the reduction in BF is most pronounced in the cerebrum, less in the cerebellum, and least in the brainstem, (M±SE, 58±7%,


34±12%, 27±11% reduction from control respectively, p