Two different techniques of facial mask induction of anesthesia in children provide identical intubation conditions despite different anesthetic depth.

BACKGROUND: Sevoflurane induction in chil- dren is performed using different techniques. Constricted, centered, and symmetrical pupils (CCSP) are classically the endpoint to be achieved before laryngoscopy is performed.

OBJECTIVES: We investigated whether two different inhalation induction techniques with the same clinical end- point provided similar intubating conditions and comparable depth of anesthesia as assessed by the Bispectral Index (BIS).

METHODS: Following IRB approval, and informed parental consent, 20 children were recruited. They were sched- uled for general anesthesia with tracheal intubation, and randomly assigned to Group 1, where the practitioner used 6% inspired sevoflurane in 50% 0₂/N₂0, and no manually assisted ventilation, or Group 2, where inspired sevoflurane was 8% in 50% 0₂/N₂0, and ventilation was manually supported upon loss of consciousness. BIS values were blinded. Laryngoscopy was performed after CCSP. Intubation conditions scoring was based on jaw relaxation (mobile = 1, partially mobile = 2, fixed = 3), position of vocal cords (open = 1, half-closed = 2, closed = 3), and cough (no cough = 1, 1 or 2 coughing efforts = 2, persistent coughing = 3). A total score > 3 corresponded to non-optimal conditions.

RESULTS: Upon CCSP, BIS values were significantly lower in Group 1 [mean (SD) : 30 (8) - 48 (18), p <0.001], despite significantly higher end-tidal sevoflurane concentration in Group 2 [mean (SD) : 5.0 (0.7) - 6.2 (0.5) ; p <0.001]. Time to CCSP was slightly shorter in Group 2. Intubation conditions were always optimal except for one patient of Group 1.

DISCUSSION: Both induction techniques achieve good intubating conditions. Possible explanations for the between-group BIS difference include variable appreciation of the CCSP endpoint, different induction lengths or sevoflurane equilibration times, or sevoflurane-induced increase in electroencephalogram power. A better indicator of the best time to intubate is needed to avoid too deep anesthesia in children.