It is known that sympathetic stimulation and increase in cerebral blood flow velocity can be induced by desflurane. Cerebral oxygen balance could be disturbed during desflurane induction. Aim of this study was to elucidate that cerebral oxygen imbalance induced by desflurane mask induction can be reduced by combination of remifentanil and hypocapnia.

Twenty ASA 1-2 subjects were allocated randomly into 5 groups divided by concentration of remifentanil (0.0, 0.5, 1.0, 1.5, and 2.0 ng/ml). After confirmation of attaining proposed concentration of remifentanil, propofol and vecuronium were administered and mechanical ventilation was done with 8% desflurane with facial mask. Subsequently, changes in regional cerebral oxygen saturation (ΔrSO₂), arterial blood pressure, heart rate, cardiac index, estimated alveolar concentration of desflurane (P_DESF), and end-tidal concentration of carbon dioxide (PET_CO2) were recorded for the following 10 minutes. According to concentration of desflurane and remifentanil, ΔrSO₂ and hemodynamic factors were checked.

During desflurane induction, changes in cerebral oximetry reached up to +10% (6 [first quartile], 13 [third quartile]). Arterial blood pressure, heart rate, and cardiac index were changed within clinical ranges. The ΔrSO₂ showed S-shaped increasing pattern according to increasing P_DESF. Hypocapnia and concentration of remifentanil reduced the maximum ΔrSO₂ (P = 0.0046, P = 0.0060). Hypocapnia also shifted the curve to left (P = 0.0001).

During 8% desflurane induction, regional cerebral oxygen saturation (rSO₂) increases maximum +25%. Hypocapnia and use of remifentanil can reduce the increase in regional cerebral oxygen saturation.