Rapid inhalation induction with 7% sevoflurane combined with intravenous midazolam

Study Objective: To identify an improved rapid inhalation induction (RII) technique by investigating hemodynamics and heart rate variability of induction with midazolam and RII with 7% sevoflurane in comparison with RII alone. Design: Prospective, randomized study. Setting: Operating room of a university hospitals. Patients: 40 patients scheduled for gastrectomy without complications. Interventions: In the sevoflurane (Sev) group, anesthesia was induced with tidal volume breathing of 7% sevoflurane with 50% nitrous oxide (N₂O) in oxygen (O₂) for 3 minutes. In the midazolam-sevoflurane group (Mid-Sev) intravenous midazolam 0.1 mg/kg was given, followed by 7% sevoflurane with 50% N₂O. In both groups, endotracheal intubation was facilitated with vecuronium 0.15 mg/kg, which was administered at loss of consciousness. Measurements: Blood pressure, heart rate, heart rate variability, time to loss of response to verbal command (sleep time), rate of body movement or cough during induction, and patient satisfaction were monitored. Main Results: Blood pressure and heart rate increased significantly in the Sev group but not in the Mid-Sev group. Heart rate was significantly higher in the Sev group at 1 minute after intubation. High-frequency component (cardiac parasympathetic activity) in heart rate variability increased before intubation, with a higher value seen in the Sev group than the Mid-Sev group. The ratio of low-frequency component to high-frequency componnt (cardiac sympathetic activity) did not change in either group. Sleep time did not differ between the two groups. The numbers of patients with body movement and cough, and patients who were not satisfied with the induction method were, respectively, four, three, and eight in the Sev group; and one, zero, and two in the Mid-Sev group. The last value was significantly higher in the Sev group (p = 0.0285). Conclusions: The addition of intravenous midazolam 0.1 mg/kg provides more stable hemodynamics, cardiac autonomic nervous system activity, and patient satisfaction in RII with 7% sevoflurane.