Low plasma lidocaine concentration does not affect oxygen uptake at awakening from isoflurane anesthesia

To clarify the effects of lidocaine in plasma after epidural administration on oxygen uptake (VO2) at awakening from isoflurane anesthesia, we measured VO2 in 45 patients undergoing abdominal hysterectomy under four conditions: control group, intravenous normal saline; epidural group, 3 mg/kg of 1.5% lidocaine epidurally as a bolus; and groups CIV-A and CIV-B, continuous intravenous infusion of 2% lidocaine, 0.5 and 1 mg/kg, respectively, for 5 min followed by 30 micrograms.kg-1 x min-1. VO2 at both periods of steady state during anesthesia before lidocaine administration and awakening from anesthesia were measured using a mass spectrometer system during spontaneous breathing. At awakening, VO2 in the control, CIV-A, and CIV-B groups increased significantly (P < 0.02) from 142 to 262-328 mL.min-1 x m-2 which as more (P < 0.01) than that in the epidural group which increased from 166 to 159 mL.min-1 x m-2. These results indicate that epidural lidocaine prevents the increase in VO2 associated with arousal from isoflurane anesthesia. This effect is not due to the absorbed plasma lidocaine but due to the epidural neural block.