Abstract
Hyperventilation (respiratory alkalosis)is an important treatment for persistent pulmonary hypertension in neonates. The precise way that hyperventilation attenuates hypoxic pulmonary vasoconstriction is unclear. We studied the effect of alkalosis on hypoxia-induced pulmonary vasoconstriction in 13 acutely instrumented neonatal lambs. We specifically examined the relative roles of a metabolic alkalosis (MA) vs a respiratory alkalosis (RA). After stabilization in each experimental situation, the lambs were made acutely hypoxic by a 1-minute inhalation of 5% O2-95% N2. The control pulmonary vasoconstrictor response to hypoxia was measured at both the beginning and end of each experiment and was compared to the responses observed after hyperventilation (RA) and after bicarbonate infusion (MA-normal PaCO2). The table gives the mean changes before and during hypoxia.
Data consider different from control 1 when p<.05 by 2-way ANOVA.
Hypoxic pulmonary vasoconstriction was significantly milder whenever the animal was alkalotic - regardless of whether the alkalosis was respiratory or metabolic. Although the rise in PVR was smaller during MA than during RA, there was no significant difference between the effects of the two types of alkalosis. In summary, the elevated pH rather than decreased PaCO2 during hyperventilation appears to be the major factor in blunting hypoxic pulmonary vasoconstriction.
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Lyrene, R., Welch, K., Dew, A. et al. AIKALOSIS ATIENUATES HYPOXIC PULYONARY VASOCONSTRICTION IN NEO NATAL LAMBS. Pediatr Res 18 (Suppl 4), 396 (1984). https://doi.org/10.1203/00006450-198404001-01820
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DOI: https://doi.org/10.1203/00006450-198404001-01820