The Effect of Desflurane and Sevoflurane on Cerebral Oximetry Under Steady-State Conditions

We studied the effect of sevoflurane and desflurane on regional cerebral oxygenation (rSO2). Twenty-two patients undergoing abdominal hysterectomy received sevoflurane and desflurane for 15 min each and 30 min apart under steady-state conditions in a randomized, crossover manner to maintain a bispectral index (BIS) of 40–50. In another 22 patients undergoing the same anesthesia and surgery BIS was maintained at 20–30. During the 15-min administration of each anesthetic at steady-state conditions rSO2, BIS, inspired and end-tidal anesthetic concentrations, end-tidal CO2, Spo2, systolic and diastolic blood pressures, and heart rate were recorded every 3 min. The rSO2 did not differ between sevoflurane and desflurane when BIS values were maintained between 40–50 or 20–30. The MACBIS values required to maintain BIS at 40–50 and at 20–30 were 1.0 versus 1.2 (P = 0.004) and 1.6 versus 1.8 (P < 0.001) for desflurane and sevoflurane respectively. Higher rSO2 values were obtained by 1.6 MAC (71 ± 13) than by 1 MAC of desflurane (66 ± 10; P < 0.001) and by 1.8 MAC (72 ± 11) than by 1.2 MAC of sevoflurane (66 ± 13; P < 0.001). In conclusion, equipotent concentrations of desflurane or sevoflurane in terms of BIS are associated with similar rSO2 values, but larger anesthetic concentrations of both anesthetics increased the rSO2 values.