Main content area

CO₂ induced acute respiratory acidosis and brain tissue intracellular pH: a ³¹P NMR study in swine

Martoft, L., Stødkilde-Jørgensen, H., Forslid, A., Pedersen, H. D., Jørgensen, P. F.
Laboratory animals 2003 v.37 no.3 pp. 241-248
acidosis, air, anesthesia, arteries, bicarbonates, blood pH, brain, breathing, carbon dioxide, euthanasia, laboratory animals, nuclear magnetic resonance spectroscopy, oxygen, phosphorus, poultry, slaughter, stable isotopes, swine
High concentration carbon dioxide (CO₂) is used to promote pre-slaughter anaesthesia in swine and poultry, as well as short-lasting surgical anaesthesia and euthanasia in laboratory animals. Questions related to animal welfare have been raised, as CO₂ anaesthesia does not set in momentarily. Carbon dioxide promotes anaesthesia by lowering the intracellular pH in the brain cells, but the dynamics of the changes in response to a high concentration of CO₂ is not known. Based on ³¹P NMR spectroscopy, we describe CO₂-induced changes in intracellular pH in the brains of five pigs inhaling 90% CO₂ in ambient air for a period of 60 s, and compare the results to changes in arterial blood pH, PCO₂, O₂ saturation and HCO₃ ⁻ concentration. The intracellular pH paralleled the arterial pH and PCO₂ during inhalation of CO₂; and it is suggested that the acute reaction to CO₂ inhalation mainly reflects respiratory acidosis, and not metabolic regulation as for example transmembrane fluxes of H⁺/HCO₃ ⁻. The intracellular pH decreased to approximately 6.7 within the 60 s inhalation period, and the situation was metabolically reversible after the end of CO₂ inhalation. The fast decrease in intracellular pH supports the conclusion that high concentration CO₂ leads to anaesthesia soon after the start of inhalation.