CSF-Arterial $$P_{{\text{CO}}_2 }$$ differences with and without ventriculo-cisternal perfusion in the anaesthetized cat

In experiments in pentobarbital anaesthetized cats the CO2 tensions in arterial blood and in cerebrospinal fluid (CSF) were measured with and without ventriculo-cisternal perfusion at different levels of anaesthesia. It was found that at arterial $$P_{{\text{CO}}_2 }$$ values from 30–60 mm Hg, the linear relationship between the CSF-arterial $$P_{{\text{CO}}_2 }$$ difference and the arterial $$P_{{\text{CO}}_2 }$$ was influenced by the depth of anaesthesia. However, at a “normal” $$Pa_{{\text{CO}}_2 }$$ of about 35 mm Hg the CSF-arterial $$P_{{\text{CO}}_2 }$$ difference was about the same at different levels of anaesthesia. During ventriculo-cisternal perfusion the CSF-arterial $$P_{{\text{CO}}_2 }$$ difference was found to be about 3 mm Hg higher than in the unperfused cat.