Dose Finding Study of Remimazolam for Laryngeal Mask Airway Insertion

Laryngeal mask airways (LMA) are widely used in patients receiving general anesthesia and are known to have the following advantages over the endotracheal tube: lower incidence of postoperative sore throat, lower incidence of cough during emergence, and lower incidence of postoperative vomiting. Although LMAs can be inserted without the use of muscle relaxants, a sufficient depth of anesthesia is necessary for placement. Remimazolam is a newer anesthetic that is ultra-short acting with a rapid onset and short context-sensitive half-life allowing for fast recovery. However, the dose of remimazolam needed for LMA insertion without muscle relaxants is not well known. This dose-finding study aims to find the ED50 and ED95 of a single bolus dose of remimazolam for LMA insertion without muscle relaxants in adult patients.

This is an interventional study done in a single group using the Dixon's up-and-down method which requires at least six success/failure pairs in the same direction. The primary endpoint of this study is to investigate the dose of remimazolam associated with 50% (ED50) and 95% (ED95) probability for adequate depth of anesthesia for LMA insertion without muscle relaxants. The beginning dose of remimazolam is 0.3 mg/kg, and when LMA insertion is successful, the dose will be decreased by 0.05 mg/kg in the next patient. When LMA insertion is unsuccessful (failed), the dose will be increased by 0.05 mg/kg in the next patient. Successful LMA insertion is defined as symmetrical chest wall movement and square-wave capnographic traces observed with manual ventilation.