Abstract
Previous studies in adults have shown that CO2 is a major factor in cerebral blood flow regulation. The present study investigates the effect of hyperventilation on cerebral and other organs blood flow in 8 newborn lambs 15 days old. Following chronic catheterization,blood gases, Hct, Hb, pH, lactates, pyruvates, and regional blood flows using the microsphere technique were obtained prior to and following hyperventilation. Mean values for blood flow ± SD in ml/min/100g tissue at a baseline PaCO2 of 36 mmHg and after hyperventilation to 20 and 12 mmHg respectively were: brain - from 118 ± 14 to 83 ± 10 to 59 ± 17 (p < 0.05); adrenal - from 418 ± 60 to 365 ± 45 to 303 ± 40 (p < 0.05); kidney - from 458 ± 49 to 408 ± 31 (p < 0.05) to 201 ± 42 (p < 0.01); heart - from 111 ± 32 to 88 ± 21 to 59 ± 15 (NS). Cardiac output did not significantly change from a mean value ± SD in ml/min/kg of 197 ± 39 to 161 ± 33 to 108 ± 24 at 20 and 12 mmHg respectively. There was no change in whole blood buffer base with acute changes in PaCO2. This data demonstrates that hyperventilation reduced organ blood flow independent of cardiac output. Cerebral blood flow in the newborn lambs as in the adults seems sensitive to changes in PaCO2 with the reduction being most marked (50% from baseline value) at a PaCO2 of 12 mmHg. These data also suggest that a similar mechanism may be responsible for the reduction in renal and adrenal blood flows.
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Kumar, S., Karathanos, A., Rabin, A. et al. 127 REGIONAL BLOOD FLOW RESPONSE TO CHANGES IN ARTERIAL CARBON DIOXIDE TENSION (PaCO2) IN NEWBORN LAMBS. Pediatr Res 12 (Suppl 4), 385 (1978). https://doi.org/10.1203/00006450-197804001-00132
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DOI: https://doi.org/10.1203/00006450-197804001-00132