Rapid sevoflurane induction compared with thiopental.

STUDY OBJECTIVES

To examine whether the speed of induction of anesthesia with sevoflurane/nitrous oxide (N2O) utilizing a 10-second vital capacity rapid inhalation induction (VCRII) followed by tidal breathing was similar or faster than cautious intravenous (i.v.V) thiopental induction with inhaled N2O.

DESIGN

Prospective, randomized, double-blinded study.

SETTING

Veterans Affairs Medical Center.

PATIENTS

50 male ASA physical status I, II, and III patients scheduled for general anesthesia.

INTERVENTIONS

Patients were randomized to receive either 8% sevoflurane or i.v. thiopental. Patients were allocated to one of two groups of 25 patients each. In both groups, the breathing circuit was initially primed for 5 minutes with (4 L/min) and O2 (2 L/min), while the Y-piece was occluded. In the sevoflurane group, the circuit was additionally primed with 8% sevoflurane. Patients were trained to perform a vital capacity breath. After maximal exhalation, the occluding plug was rapidly removed from the Y-piece and connected to the facemask. The patient then inspired to vital capacity, held his breath for 10 seconds, and then was allowed to breathe normally. At the end of the 10-second breathhold, and as the patient started normal breathing, either thiopental (thiopental group) or normal saline (sevoflurane group) was injected at a rate of 4 mL every 10 seconds.

MEASUREMENTS

A study-blinded observer recorded the time to induction, as defined by the time to loss of eyelash reflex, and noted the occurrence of side effects.

MAIN RESULTS

The speed of induction was the same for both groups (p > 0.05). An average of eight breaths was required before loss of eyelash reflex. Side effects occurred in 36% of the patients in the thiopental group, and 32% in the sevoflurane group (p > 0.05); these were minor and did not affect induction.

CONCLUSION

Sevoflurane/N2O VCRII as used in this investigation is an effective inhalation technique; it resulted in an induction time similar to that of slow i.v. thiopental with inhaled N2O.