Facilitation of laryngeal mask insertion. Effects of lignocaine given intravenously before induction with propofol.

The effects of pretreatment with lignocaine administered intravenously on the insertion of the laryngeal mask airway were investigated in 80 unpremedicated, ASA 1 or 2, adult day-case patients in a randomised, double-blind, placebo-controlled trial. Patients received either intravenous lignocaine 1.5 mg.kg-1 or an equivalent volume of sodium chloride 0.9%. Induction of anaesthesia was achieved with propofol given via a syringe driver at a fixed rate of 600 ml.h-1 until the patient dropped a weighted syringe. No opioid or sedative drugs were given prior to induction. Pain on injection of propofol was recorded. Jaw opening, ease of insertion of the laryngeal mask, coughing, gagging and airway patency were all scored on three-point scales immediately after mask insertion re-attempted. This cycle was continued until success was achieved and the number of such cycles recorded. There were no differences between the lignocaine and control groups with respect to induction dose of propofol, degree of jaw opening, or amount of gagging. Laryngeal mask insertion was facilitated by pretreatment with lignocaine administered intravenously, without an alteration in induction dose of propofol (p < 0.05). Coughing and airway obstruction were both significantly reduced by pretreatment with lignocaine, as was the incidence of failure of insertion requiring deepening of anaesthesia (p < 0.05).