Vital capacity induction with 8% sevoflurane and N₂O causes cerebral hyperemia

Abstract

Purpose. Little is known about the influence of high-dose sevoflurane on cerebral volume. We evaluated induction time and cerebral blood volume with 8% sevoflurane using the “vital capacity induction” technique.

Methods. Thirty-four patients were randomly allocated into three groups. Group P received 2.0 mg·kg⁻¹ of propofol i.v. and inhalation of 67% N₂O/O₂, whereas group S5 and group S8 received inhalation of primed 5% and 8% sevoflurane in 67% N₂O/O₂, respectively. Induction time was measured as the time from the start of inhalation, or from the end of injection, until loss of eyelash reflex. Near-infrared spectroscopy and bispectral index (BIS) were monitored continuously until 3 min after tracheal intubation.

Results. Induction time was less in group S8 (17.3 ± 6.4 s, mean ± SD) than in groups P (25.7 ± 8.2 s) and S5 (33.0 ± 16.8 s). There was a significant increase in cerebral blood volume after intubation in group S8, as suggested by higher cerebral oxyhemoglobin and total hemoglobin levels. There were no differences in BIS scores among the groups during the study period.

Conclusion. Vital capacity inhalation of 8% sevoflurane produces a faster loss of eyelash reflex than does 5% sevoflurane or propofol, but increases cerebral blood volume.