Ease of Laryngeal Mask Airway Insertion – Comparison of Propofol versus Thiopentone and Lignocaine in Adult Patients

Abstract

Background: A patient is required to be fully relaxed and airway reflexes should be adequately suppressed to allow for smooth insertion  of a laryngeal mask airway (LMA).Propofol and a variety of other induction agents and their combinations have been tried to ease its  insertion. The use of cheaper alternatives in our environment is highly desirable.

Aims and objectives: To compare the ease of insertion  of LMA in patients given propofol alone versus thiopentone with lignocaine, as well as assessing the cost effectiveness of these agents in  our hospital setting.

Methods: This is arandomised single blind prospectivestudy carried out in a Public Tertiary Academic Health Institution. Sixty-four ASA I and II patients equally randomized into 2 groups scheduled for short (not lasting more than one hour)  elective gynaecological, orthopaedic, urological and general surgical procedures were recruited into this study. Patients were  premedicated with 1g.kg-1 fentanyl intravenously and pre-oxygenated for five minutes. This was followed by an induction dose of either 2.5mg.kg^-1 propofol (group A) or a sequence of 2mg.kg^-1 lignocaine and 5mg.kg^-1 thiopentone (group B) given by a trained assistant.  With the patients in the sniffing position, LMA insertion was attempted immediately after induction of anaesthesia by the anaesthetist  (researcher) who observed the ease of LMA insertion using presence or absence of adverse airway responses to LMA insertion such as  coughing, gagging, laryngospasm, head and limb movement or inadequate jaw relaxation. These responses were graded as; no  response, mild response, moderate response and severe response. Overall assessment of the ease of LMA insertion was then done  combining these graded adverse airway responses as; excellent if there were no adverse airway responses, good if responses were mild,  satisfactory if responses were moderate and poor if responses were severe with additional anaesthetic required to allow LMA insertion.

Results: The average age in group A was 36.5±14 whereas in group B it was 38.7±05 with the p=0.493.There were 22 (56.4%) male patients  in group A compared to 17 (43.6%) male patients in group B with p=0.528; whereas, there were 10 (40.0%) female patients in  group A compared to 15 (60.0%) female patients in group B with p=0.326. Excellent LMA insertion were observed in 28 (87.5%) patients in  group A compared to 27 (84.4%) patients in group B (P= 0.893); Good LMA insertion in 2 (6.3%) patients in group A compared to 1 (3.1%)  patient in group B (p= 0.564); Satisfactory in 2 (6.3%) patients in group A compared to 4 (12.5%) patients in group B (p= 0.655).  

Conclusion: Thiopentone together with Lignocaine provided optimum conditions for laryngeal mask airway insertion comparable to that provided by propofol alone.