Pharmacokinetics of Perioperative Lignocaine

The following describes the use of lignocaine for all patients at the study site, regardless of whether they participate in this study. Lignocaine infusions will be initiated in the operating theatre at induction of anaesthesia. The attending anaesthetist will be responsible for preparation of lignocaine for infusion according to their institutional protocol. All patient's included in the study would be planned to receive a lignocaine bolus and infusion as part of their anaesthetic and/or post-operative care regardless of their involvement in the study. An intravenous bolus (loading) dose and continuous infusion will be administered using the following protocol: Bolus Dose: Following anaesthesia induction, a bolus of intravenous lignocaine will be delivered slowly over the course of 2-3 minutes Dosed at 1.5mg/kg to a maximum of 150mg Dosing will be based on ideal body weight (IBW) according to the Devine formula. Continuous Infusion: After the bolus dose has been delivered a lignocaine infusion at 1.5mg/kg/hr (to a maximum of 150mg/hr) will be commenced via an infusion pump. Dosing will be based on ideal body weight according to the Devine formula. The duration of the infusion and decision of when to cease will be at the discretion of the attending anaesthetist or pain physician (if the patient has been admitted to the ward). IV lignocaine infusions will be administered up to 48 hours. Ward management of the IV lignocaine infusion will be according to institutional lignocaine infusion protocols. If toxicity develops the patient will be reviewed by the Pain Service or On-call anaesthetist and lignocaine infusion stopped or titrated down as per the institutional lignocaine infusion policy. The Devine Formula for Ideal Body Weight: Male ideal body weight(kg) = 50 + (0.91 * (Height in cm -152.4)) Female Ideal body weight (kg) = 45.5 + (0.91 * (Height in cm -152.4)) Intraoperative and Postoperative phase: - Peripheral blood collection for the quantification of lignocaine concentration (free and bound), metabolite concentration and Alpha 1 acid glycoprotein levels - Documentation of any adverse symptoms associated with the use of lignocaine from the induction of anaesthesia until 4 hours after the lignocaine infusion is ceased. This will be done as brief questioning in recovery and every 24 hours (out to 48 hours following infusion start) take roughly 5 mins for each session. This is done as part of standard care on lignocaine infusion currently so does not represent a deviation from normal care. A total of 8 lignocaine levels will be done during the study period. 3 levels will be done intra-operatively, shortly prior to and after starting the infusion. The remaining 5 will be completed over the remaining 48 hours (with 3 levels shortly after cessation of the infusion). Each blood test is anticipated to take roughly 5-10 minutes.