Comparison of Two Doses of Intravenous Dexmedetomidine as Premedication for Laryngeal Mask Airway Insertion in Adults: A Randomised Clinical Trial

Abstract

Introduction: The Laryngeal Mask Airway (LMA) has gained popularity in recent years for both rescue ventilation as well as airway management device for General Anaesthesia (GA). Adequate jaw relaxation and blunting of airway reflexes prevents haemodynamic changes during LMA insertion. Several drugs have been used as adjuncts to Intravenous (IV) Propofol, of which Dexmedetomidine in a dose of 1 μ/kg is now gaining popularity. But at this dose significant bradycardia has been observed. Hence, the study aimed at comparing 1 µ/kg of Dexmedetomidine, with a lower dose of 0.8µ/kg to assess the same. Aim: To compare two different doses of intravenous dexmedetomidine 0.8 µg/kg and 1 µg/kg as premedication with propofol 2 mg/kg for ease of insertion of LMA, attempts at LMA insertion and secondary objectives included, additional propofol requirements, adverse effects. Materials and Methods: The present study was a randomised double blind clinical trial in which a total of 180 American Society of Anesthesiologists (ASA) grade I and II patients undergoing short procedures under GA not exceeding more than two hours were included. Those with Heart Rate (HR) <60 bpm (beats per minute), on beta blockers, restricted mouth opening were excluded. The patients were randomly divided into group 1 and 2 who received dexmedetomidine at 0.8 µg/kg and 1 µg/kg as an infusion over 10 minutes, respectively. HR, Respiratory Rate (RR), Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP) were noted before dexmedetomidine administration, after administration, 30 seconds after induction and 1, 3, 5 ,10, 15, 20 and 25 min after LMA insertion, conditions for LMA insertion were assessed using Muzi M et al., score which includes (Jaw mobility was graded as: 1-fully relaxed; 2-mild resistance; 3-tight but opens; 4-close. Coughing/movement were graded as: 1-none; 2-one or two coughs; 3-three or more coughs; 4-bucking/movement), number of attempts at LMA insertion, additional doses of propofol if administered, adverse effects. Statistical analysis was done using Independent t-test, Chi-square test and p-value <0.05 was considered statistically significant. Results: The conditions for LMA insertion were adequate and comparable in both groups with 94.4% of patients in group 1 and 91.1% patients in group 2 having a Muzi M et al., score of 2 (jaw mobility graded as- fully relaxed and coughing/movement graded as- none). Five patients in group 1 and eight patients in group 2 had more than one attempt at LMA insertion (p-value of 0.303). There was statistically significant drop in HR in group 2 compared to group 1 (p-value <0.001). Also, a statistically significant drop in SBP, DBP, MAP in group 2 compared to group 1 was observed. There was no statistically significant difference in the requirement for additional propofol bolus in the two groups. Conclusion: IV dexmedetomidine 0.8 µg/kg used as premedication, administered as an infusion over 10 min provides smooth LMA insertion conditions and can be used as a safer alternative to IV dexmedetomidine 1 µg/kg

Keywords

• bradycardia
• double blind study
• haemodynamics
• muzi m et al score