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- Title
Trans-cerebral HCO<sub>3</sub> − and PCO<sub>2</sub> exchange during acute respiratory acidosis and exercise-induced metabolic acidosis in humans.
- Authors
Caldwell, Hannah G; Hoiland, Ryan L; Smith, Kurt J; Brassard, Patrice; Bain, Anthony R; Tymko, Michael M; Howe, Connor A; Carr, Jay MJR; Stacey, Benjamin S; Bailey, Damian M; Drapeau, Audrey; Sekhon, Mypinder S; MacLeod, David B; Ainslie, Philip N
- Abstract
This study investigated trans-cerebral internal jugular venous-arterial bicarbonate ([HCO3−]) and carbon dioxide tension (PCO2) exchange utilizing two separate interventions to induce acidosis: 1) acute respiratory acidosis via elevations in arterial PCO2 (PaCO2) (n = 39); and 2) metabolic acidosis via incremental cycling exercise to exhaustion (n = 24). During respiratory acidosis, arterial [HCO3−] increased by 0.15 ± 0.05 mmol ⋅ l−1 per mmHg elevation in PaCO2 across a wide physiological range (35 to 60 mmHg PaCO2; P < 0.001). The narrowing of the venous-arterial [HCO3−] and PCO2 differences with respiratory acidosis were both related to the hypercapnia-induced elevations in cerebral blood flow (CBF) (both P < 0.001; subset n = 27); thus, trans-cerebral [HCO3−] exchange (CBF × venous-arterial [HCO3−] difference) was reduced indicating a shift from net release toward net uptake of [HCO3−] (P = 0.004). Arterial [HCO3−] was reduced by −0.48 ± 0.15 mmol ⋅ l−1 per nmol ⋅ l−1 increase in arterial [H+] with exercise-induced acidosis (P < 0.001). There was no relationship between the venous-arterial [HCO3−] difference and arterial [H+] with exercise-induced acidosis or CBF; therefore, trans-cerebral [HCO3−] exchange was unaltered throughout exercise when indexed against arterial [H+] or pH (P = 0.933 and P = 0.896, respectively). These results indicate that increases and decreases in systemic [HCO3−] – during acute respiratory/exercise-induced metabolic acidosis, respectively – differentially affect cerebrovascular acid-base balance (via trans-cerebral [HCO3−] exchange).
- Publication
Journal of Cerebral Blood Flow & Metabolism, 2022, Vol 42, Issue 4, p559
- ISSN
0271-678X
- Publication type
Article
- DOI
10.1177/0271678X211065924