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 intra venous lignocaine 1.5 mg.kg(-1) or an equivalent volume of sodium chlo ride 0.9%. Induction of anaesthesia was achieved with propofol given v ia 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 pri or to induction. Pain on injection of propofol was recorded. Jaw openi ng, ease of insertion of the laryngeal mask, coughing, gagging and air way patency were all scored on three-point scales immediately after ma sk insertion. If insertion failed, anaesthesia was deepened by gentle manual ventilation for 1 min with nitrous oxide/oxygen/2% enflurane an d insertion re-attempted. This cycle was continued until success was a chieved and the number of such cycles recorded. There were no differen ces between the lignocaine and control groups with respect to inductio n dose of propofol, degree of jaw opening, or amount of gagging. Laryn geal mask insertion was facilitated by pretreatment with lignocaine ad ministered intravenously, without an alteration in induction dose of p ropofol (p < 0.05). Coughing and airway obstruction were both signific antly reduced by pretreatment with lignocaine, as was the incidence of failure of insertion requiring deepening of anaesthesia (p < 0.05).