Cerebrospinal fluid (CSF) and arterial and venous blood samples were collected every 15 min during 45 min of normocapnia and 90 min of hypercapnia in 10 isoflurane-anaesthetized foals. CSF samples were collected by subarachnoid catheter placed in the atlanto-occipital space. Comparison of blood and CSF gases during normocapnia indicated that CSF was significantly more acidic than blood. The lower pH was attributable to higher CO2 and lower bicarbonate concentrations than those in blood. During hypercapnia, CSF CO2 increased and pH decreased parallel to changes in blood, but changes were not as great as similar changes in venous blood, indicating that some degree of buffering occurs in the CSF of foals. It is concluded that normal CSF acid-base status in equine neonates is similar to that in other domestic species. The blood-brain and blood-CSF interfaces in neonates allow rapid diffusion of CO2, but allow only slow diffusion of bicarbonate. Equine neonates are capable of buffering respiratory-induced acid-base changes in the CSF, but the buffering capacity is less than that of the vascular compartment.
- acid base equilibrium bicarbonates blood blood gases buffering capacity carbon dioxide cerebrospinal fluid foals hypercapnia newborn animals pH horses hydrogen ion concentration potential of hydrogen Equus Equidae Perissodactyla mammals vertebrates Chordata animals ungulates eukaryotes
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