The Optimal Time to Put Laryngeal Mask Airway in the Mouth Under General Anesthesia

General Anesthesia

Laryngeal mask airway (LMA) is routinely used for some patients who have surgery under general anesthesia. LMA is placed in the mouth and allow the anesthesia to be given without having to put a breathing tube in the throat. Previous studies have focused on the effect of different anesthesia medicines on optimal condition for LMA use. The objective of the present study is to find the optimal time for LMA insertion.

This is a randomized, controlled, blinded trial. Midazolam, 2 mg and fentanyl 1.0 µg/kg, would be given prior to induction with propofol, 2.5 mg/kg. The investigator who does the induction of general anesthesia will also be responsible for the timekeeping. For this reason, it is not possible for this investigator to be blinded to randomization. The induction would conclude after loss of eyelash reflex (LER). At that point insertion of the LMA (#4 for females, #5 for males) will occur 0, 60 and 90 seconds after LER. The LMA will be lubricated with a water soluble gel and will be inserted with a deflated cuff according to the technique described by Brain. The investigator who inserts the LMA (Inv1) will be in the operating room and blinded to randomization groups by not seeing the induction of general anesthesia. This investigator will insert the LMA only when called by the investigator who induces general anesthesia (Inv2). Inv1 will also grade ease of LMA insertion. The primary outcome is Jaw opening at the time of LMA insertion, defined as full 1, partial 2, and nil 3. Secondary outcomes include: 1. Insertion of LMA (easy, difficult, impossible) 2. Coughing or gagging (none, some, significant) 3. Head or body movement (none, some, significant) 4. Laryngospasm or airway obstruction (none, partial, total)

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