Comparison of propofol and propofol/ thiopentone admixture for ProsealTM insertion

Background: The ProsealTM is commonly used for airway management during general anesthesia in Ratchaburi Hospital. Intravenous propofol (1%) has been used as an induction of choice for LMA insertion. However, the recommended dose of propofol 2.5 mg.kg-1 given intravenously could be associated with cardiovascular and respiratory depression. Objectives: to assess insertion condition and hemodynamic responses by comparing propofol (1%) and an admixture of propofol 0.5% and thiopentone 1.25% (1:1) during induction of anesthesia. Methods: In a prospective, randomized controlled study, 190 nonpremedicated patients undergoing elective surgery were allocated into two groups: Group P received propofol 1%. Group PT received an admixture of propofol 0.5% and thiopentone 1.25% (1:1), both at a dose of 0.25 ml.kg-1. The insertion condition, ease of insertion, apnea time and hemodynamic responses between the two groups were assessed. Results: The incidences of resistance to mouth opening, resistance to insertion and coughing were significantly higher in the PT group than the P group (P = 0.017). There was no difference in terms of swallowing, movement and apnea time between the two groups. None of patients developed laryngospasm. Decrease in MAP and HR during administration of Propofol - thiopentone admixture was significantly less than administration of Propofol alone. Conclusions: In nonparalyzed patients, propofol provides better conditions and easier ProsealTM insertion, but has greater hemodynamic instability than an admixture of propofol 0.5% and thiopentone 1.25% (1:1).