The role of blood pressure versus oxygen administration on cerebral oxygenation during and after anaesthesia induction A prospective cohort study

BACKGROUND The effect of anaesthesia induction on cerebral perfusion is complex due to the coinciding respiratory and haemodynamic changes that occur. OBJECTIVE To examine how changes in blood pressure and oxygen administration are related to cerebral oxygenation and its progression over time during and after anaesthesia induction. DESIGN Prospective observational study. SETTING Dutch tertiary hospital from October 2019 to May 2022. PATIENTS Two hundred and fifty-one elective cardiac surgery patients of which 188 were included in the analysis. MAIN OUTCOME MEASURES Continuous cerebral oxygenation, measured using near-infrared spectroscopy (NIRS)-based regional cerebral tissue oximetry, was assessed in relation to mean arterial pressure (MAP), partial pressure of end-tidal oxygen (PetO₂) and fraction of inspired oxygen (FiO₂) during and after anaesthesia induction. Cerebral oxygenation between subgroups with and without the occurrence of postinduction hypotension (PIH) (defined as a MAP <65 mmHg for >60 s) was compared. PetO₂ was used as a measure for the efficacy of oxygen administration to assess the effect of a high FiO₂ of 1.0 on cerebral oxygenation. RESULTS Cerebral oxygenation and PetO₂ increased during anaesthesia induction with the use of a FiO₂ of 1.0, while blood pressure decreased. All parameters decreased after anaesthesia induction, but the timing of onset of decline in cerebral oxygenation coincided with the moment that the FiO₂ was adjusted from high to low, whereas it preceded the decline in MAP by 16.4 s (95% confidence interval (CI), 2.4 to 30.4; P = 0.02). The occurrence of PIH, which comprised of 42% of our study population, did not affect cerebral oxygenation. During anaesthesia induction and the use of a FiO₂ of 1.0, cerebral oxygenation increased by 0.14% (95% CI, 0.12 to 0.16; P < 0.001) per percentage point increase in PetO₂. CONCLUSION Changes in regional cerebral tissue oximetry during and after anaesthesia induction are more related to changes in oxygen administration than blood pressure.