1354 ADAPTATION OF BRAIN BLOOD FLOW (BBF) TO PROLONGED HYPERCARBIA (PHC) IN THE NEWBORN PIGLET (P)

Abstract

In adult animals, hypercarbia-induced cerebral hyperemia may recede to normal, possibly because of the modulating effect of normalization of brain tissue pH (BtpH). Furthermore, if BtpH normalizes during PHC, a further reduction in BBF (below baseline (B)) may occur during the recovery (normocarbia, (NC)) phase. To test these hypotheses, 7 awake P's were exposed to PHC (PaCO₂ 60-70) for 4 hrs. followed by 3/4 hr. of NC. BBF (microsphere method, ml·min⁻¹ 100g⁻¹), BtpH (Roche glass electrode) and blood gases were measured during B, ½, 2 & 4 hrs. of PHC and ¼ & 3/4 hrs. during the NC recovery phase. Results appear below (M±SD):

BBF increased significantly during PHC; at 4 hrs. of PHC a slight reduction of BBF was observed when compared to the ½ hr. PHC value. BtpH was significantly reduced throughout PHC. During NC, BBF and BtpH were similar to B values. We conclude that in newborn P, the PHC results in persistent cerebral hyperperfusion resulting from a lack of BtpH normalization.

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