Induction Time Required for Successful Laryngeal Mask Airway Insertion with Sevoflurane and No Muscle Relaxant in Children

Abstract

The laryngeal mask airway (LMA) is a simple and safe method for airway control in children.We therefore determined, with meaningful confidence intervals, the time required for successful insertion of LMA in 95% of children with 8 vol% inspired sevoflurane and no muscle relaxant. Methods:Forty-six patients, ASA physical status I or II, aged 12−108 months old who were scheduled to undergo elective surgery were included.Patients received 5 mg/kg of thiopental and 0.02 mg/kg of atropine intravenously.After loss of the eye lid reflex, we applied an anesthesia circuit prefilled with 8 vol% dialed sevoflurane in 100% O2.A classic LMA (# 2) insertion was attempted after a predetermined induction time.A probit analysis was used to determine the induction time required to achieve 50% and 95% success rates during LMA insertion. Results:A probit model of induction time was predictive of successful intubation (P = 0.155).The induction times needed to achieve 50% and 95% successful LMA insertion were 125 s (95% confidence interval, 52−146 s) and 208 s (178−382 s), respectively. Conclusions:Ninety five percent success can be obtained with approximately 208 s for ages one to 9 years with classic LMA (# 2).The induction time can vary by LMA size and induction methods.Therefore further studies using different sizes of LMA and induction methods are needed.