Differential regional cerebrovascular reactivity to end-tidal gas combinations commonly seen during anaesthesia: A blood oxygenation level-dependent MRI observational study in awake adult subjects

We examined awake participants under carefully controlled end-tidal gas concentrations to assess how regional CVR changes may present with end-tidal gas changes seen commonly with anaesthesia. DESIGN Observational study. SETTING Tertiary care centre, Winnipeg, Canada. The imaging for the study occurred in 2019. SUBJECTS Twelve healthy adult subjects. INTERVENTIONS Cerebral BOLD response was studied under two end-tidal gas paradigms. First end-tidal oxygen (ETO2) maintained stable whereas ETCO2 increased incrementally from hypocapnia to hypercapnia (CO2 ramp); second ETCO2 maintained stable whereas ETO2 increased from normoxia to hyperoxia (O2 ramp). BOLD images were modeled with end-tidal gas sequences split into two equal segments to examine regional CVR. MAIN OUTCOME MEASURES The voxel distribution comparing hypocapnia to mild hypercapnia and mild hyperoxia (mean FIO2 = 0.3) to marked hyperoxia (mean FIO2 = 0.7) were compared in a paired fashion (P 
Source: European Journal of Anaesthesiology - Category: Anesthesiology Tags: Anaesthesia Source Type: research