Arterial blood concentration of sevoflurane during single-breath induction and tracheal intubation in gynecologic patients

Abstract

Study objective: To investigate sevoflurane blood concentrations on loss of consciousness during single-breath induction and ensuing tidal volume ventilation.

Design: Prospective study.

Setting: Operating room, medical center.

Patients: 12 ASA physical status I and II women scheduled for for gynecologic surgery with general anesthesia.

Interventions: All patients were instructed in the vital capacity technique for inhalation induction with primed inspired sevoflurane greater than 7% in 6 L per minute oxygen. Immediately after loss of consciousness, assisted tidal volume ventilation with a fixed 3.5% of sevoflurane was applied for 9 minutes. Tracheal intubation was performed for each patient following succinylcholine 1.5 mg/kg.

Measurements: Inspired and end-expired sevoflurane concentration, blood pressure, and heart rate were recorded. Meanwhile, arterial blood samples were collected via a radial arterial catheter on loss of consciousness as the 0 minute and at the following 1.5th, 3rd, 4.5th, 6th, and 9th minute and determined for sevoflurane concentrations by gas chromatography.

Main results: All 12 patients achieved vital capacity induction uneventfully. The mean time of loss of consciousness was 63.0 +/- 16.6 seconds. The arterial blood concentration of sevoflurane was 1.65% +/- 0.53% on loss of consciousness, equaling to that (1.67% +/- 0.26%) at the third-minute ventilation of 3.5% sevoflurane. The blood concentration at the ninth minute was 2.07% +/- 0.26%.

Conclusion: The depth of sevoflurane after 9 minutes of ventilation of 3.5% sevoflurane is not sufficient to suppress intubation-induced hemodynamic response.