Assessment of Ease of Insertion of Laryngeal Mask Airway Comparing different Doses of Suxamethonium with Etomidate: A Comparative Randomised Double-blind Controlled Study

Abstract

Introduction: Laryngeal mask airway (LMA) is used more often in today’s anaesthesia practice. Smooth and successful insertion needs proper mouth opening and minimal or no airway reflexes such as gagging, coughing, or laryngospasm. Induction agents like propofol and etomidate are known to blunt the laryngeal reflexes but often patient movement, coughing, and gagging create an unpleasant situation. Aim: To assess the effects of suxamethonium 0.25 mg/kg, and 0.5 mg/kg, and placebo (normal saline) on the facilitation of laryngeal mask airway insertion along with etomidate as an induction agent in order to achieve haemodynamic stability and fewer complications. Materials and Methods: This was a double-blind randomised controlled study, which included, a total of 90 adult patients, American Society of Anaesthesiologists (ASA) class I-II, scheduled for minor surgery under general anaesthesia and was conducted from December 2021 to February 2022, at Malla Reddy Medical College for Woman, Hyderabad, Telangana, India. The total participants were randomly allocated into three groups (Normal Saline (NS), S1 and S2). The group NS (placebo) received normal saline, and Group S1 and S2 received injections of suxamethonium 0.25 mg/kg, or 0.5 mg/kg, respectively. Induction of anaesthesia was performed with a bolus dose of etomidate 0.3 mg/kg. Study drugs were administered when the patient had lost consciousness. Laryngeal mask airway size 3 or 4 (as appropriate) was inserted. Relaxation of the jaw, coughing, gagging, laryngospasm, and any patient movements was observed during the insertion of LMA. The overall insertion conditions were graded according to modified scheme of Lund and Stovner. The statistical analysis was carried out by using Chi-square test, Fisher’s-Exact test and Bonferroni’s t-test. Results: A total of 89 patients were analysed (group NS: n=29, group S1: n=30, group S2: n=30). Good jaw relaxation (absolutely relaxed with no muscle tone) was noted in 16 patients of group S2, 12 in group S1, and 2 in group NS (p<0.001). There was significant difference in coughing and gagging among the three groups (p=0.041). However, in the group NS, eight patients had mild movement and six had moderate movement during the insertion of LMA (p=0.002). Overall insertion conditions were better in suxamethonium groups (p=0.0001). Conclusion: Etomidate as the sole induction agent for LMA insertion is not ideal. Concurrent use of a low dose of suxamethonium (0.5 mg/kg) might significantly obtund the airway reflexes in response to LMA insertion.

Keywords

• coughing
• general anaesthesia
• laryngospasm
• low dose