High concentration versus incremental induction of anesthesia with sevoflurane in children: a comparison of induction times, vital signs, and complications

Abstract

Study objective: To compare sevoflurane induction times and complications in children during a high concentration, primed-circuit method and an incremental induction technique.

Design: Randomized, prospective open-label study.

Setting: Academic university hospital.

Patients: 40 unpremedicated ASA physical status I and II children age 4 months to 15 years undergoing elective surgical procedures with general anesthesia.

Interventions: Patients were randomized to one of two study groups. In the high concentration group, the anesthesia circuit was primed with 8% sevoflurane in a 2:1 nitrous oxide:oxygen (N2O:O2) mixture. Patients breathed this gas mixture spontaneously until loss of the eyelash reflex. In the incremental group, the face mask was applied and 1% sevoflurane in a 2:1 N2O:O2 mixture was administered. In this group, the sevoflurane concentration was increased by 1% every 2 to 3 breaths. Gas flows of 6 L/min were administered to both groups during the study period. Following loss of the eyelash reflex, the sevoflurane concentration was decreased to 5% until a depth of anesthesia sufficient to start an intravenous catheter was achieved.

Measurements and main results: Induction cooperation, induction time (face mask application to loss of the eyelash reflex), one-minute vital signs [blood pressure, heart rate, oxygen saturation via pulse oximetry (SpO2)], induction complications. Induction of anesthesia was faster in the high concentration group than in the incremental group (mean (SD) 42 (9) sec vs. 66 (12) sec, respectively; p < 0.001). Induction complications were minor and occurred with similar frequencies (4/20 patients vs. 3/20 patients). There were no significant intergroup heart rate, blood pressure, or SpO2 differences during induction. No patients required treatment for hypotension or bradycardia.

Conclusions: In healthy pediatric patients undergoing mask induction of general anesthesia with sevoflurane, the induction time can be significantly shortened without an increase in the frequency of airway or vital sign complications using a high concentration, primed circuit technique compared with a conventional, incremental induction method.