Regional cerebral oxygen saturation during induction of general anesthesia in the elderly

Introduction: Hypotension caused by induction of general anesthesia, if associated to a reduction in cerebral blood flow, could cause a potentially harmful decrease in cerebral oxygenation. Aims: Aim of the present study was to evaluate the effects of general anesthesia induction on regional cerebral oxygen saturation (rSO2) in patients aged 75 and more, undergoing elective non-cardiac surgery. Methods: In 22 patients aged 79±2 years general anesthesia was induced with propofol (2.0±0.5 mg/kg). Non-invasive mean arterial blood pressure (MAP), rSO2 (SICO, Covidien, USA) and bispectral index (BIS, Covidien, USA) were continuously measured. A mean preinduction value was calculated for each variable and compared with one-way ANOVA to post-induction values, averaged every 5 minutes. Results: Anesthesia induction caused a significant reduction in MAP and BIS (p<0.05 oneway ANOVA, Figure 1), while regional cerebral oxygen saturation transiently increased (p<0.001 one-way ANOVA, Figure 2).Conclusion: Despite the significant drop in MAP no reduction in cerebral oxygen saturation was observed in our population of elderly patients during the induction of anesthesia. Preservation of cerebral blood flow through autoregulation and reduced cerebral oxygen consumption induced by anesthetic drugs could explain the finding.