Abstract
Hypocarbic RA acutely reduces brain blood flow (BBF) by 40-50%, however, most evidence in adult subjects suggests BBF normalizes during prolonged hypocarbia. We investigated the time course of this change in hyperventilated (HV) newborn piglets. Cardiac output (C.O.) and BBF (n=8) were determined by the microsphere method and brain oxygen consumption (VO2) and extraction (EO2) measured from the sagittal vein. Following baseline (B) (PaCO2 35-40) determinations, RA (PaCO2 15-20) was induced by hyperventilation. Measurements were repeated at 30, 60 and 120 minutes.
Similar timed measurements in control piglets (PaCO2 35-40) showed no significant variation over time. Acutely (30″), RA decreased BBF (40%), but this degree of vasoconstriction was not maintained. EO2 was maintained at a consistantly elevated level during RA. Thus, VO2 initially decreased but then returned to B. We speculate that RA induced a maximal increase in EO2, with the late increase in BBF representing a vascular escape phenomenon which serves to preserve VO2.
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Hansen, N., Miller, R., Nowicki, P. et al. 1409 BRAIN BLOOD FLOW ALTERATIONS DURING PROLONGED RESPIRATORY ALKALOSIS (RA). Pediatr Res 19, 345 (1985). https://doi.org/10.1203/00006450-198504000-01433
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DOI: https://doi.org/10.1203/00006450-198504000-01433