Effect of Nebulized Lidocaine on the Quality of Laryngeal Mask Airway Insertion

The primary outcome of this study will be the effect of lidocaine nebulization before LMA insertion on LMA insertion score (within 1 minute of LMA insertion) in adult patients undergoing surgery under general anesthesia. The secondary outcome measures are the effect of LMA insertion on heart rate, arterial blood pressure, SpO2, the first time insertion rate of the LMA, and postoperative complications during LMA removal (soft tissue trauma, coughing, and laryngospasm).

Patients will be randomly allocated into two groups of equal size to receive lidocaine nebulization, group L (GL) or distilled water nebulization, group W (GW/control). Randomization will be performed using GL and GW registers, which will be placed in sealed envelopes prior to study initiation and opened prior to anesthesia by a physician who will prepare the solution for nebulization and will identify it with the patient number, according to the envelope drawn. Group L patients (n = 40) will receive 10 mL lidocaine 4%, and GW patients (n = 40) will receive 10 mL distilled water (DW) by nebulizer mask 5 min prior to anesthesia. All patients will be preoxygenated with 100% oxygen for 3 minutes via mask gently placed over the face and thereafter Propofol 2.5 mg/kg slowly IV plus Fentanyl 1 µg/kg IV will be used for induction of anesthesia, and isoflurane for maintenance of anesthesia in both groups. After confirming sufficient level of anesthesia (loss of eye lash reflex and jaw relaxation), the standard technique for LMA insertion (Brain,s method) will be used in both groups. Water based jelly will be applied on the posterior surface of the LMA and pressed along the palato-pharyngeal curve using the index finger. It is finally pushed further down till resistance is felt. A size 3 LMA will be used in women and a size 4 in men. Proper placement of LMA will be confirmed with bilateral equally audible breath sounds, chest movements and square wave capnography. Patients will be allowed to breathe spontaneously after successful LMA insertion. The overall insertion condition will be assessed via a modified three point scale consisting of six variables, which include: Mouth opening (3: full; 2: partial; 1: none) Ease of insertion (3: easy; 2: difficult; 1: impossible) Swallowing (3: nil; 2: slight; 1: gross) Coughing or gagging (3: nil; 2: slight; 1: gross) Head or limbs movement (3: nil; 2: slight; 1: gross), and Laryngospasm (3: nil; 2: partial; 1: total). Total score Insertion condition 18 Excellent 16-17 Satisfactory \<16 Poor Any failure of insertion in both groups (defined as failure to insert the LMA after 3rd time), will be managed by endotracheal intubation. At the end of the operation, LMA will be removed under deep anesthesia and replaced with Guedel's airway. Oxygen will be continued with a face mask until full recovery, and then the patients will be moved to the PACU.