Effect of intravenous lidocaine on cough response to endotracheal intubation in propofol-anaesthetized dogs

Abstract Objective To determine whether the administration of intravenous (IV) lidocaine before the induction of anaesthesia in premedicated dogs reduces the cough response associated with endotracheal intubation and the propofol dose required. Study design Prospective, randomized, blinded clinical study. Animals A total of 84 client-owned dogs, with American Society of Anesthesiology physical status I and II. Methods Dogs received intramuscular (IM) acepromazine 0.02 mg kg −1 and methadone 0.3 mg kg −1 and were randomly allocated to one of two groups: saline (group S) and lidocaine (group L). Five minutes before the induction of anaesthesia and 40–50 minutes after premedication, group L received lidocaine (1.5 mg kg −1 ) and group S received an equal volume of saline solution, each administered slowly IV. Anaesthesia was induced with propofol, initially 2 mg kg −1 IV over 40 seconds, and then in increments of 0.5 mg kg −1 every 15 seconds to effect. The same investigator anaesthetized all cases, unaware of group allocation. The following parameters were recorded: pulse rate (PR), mean arterial pressure (MAP, oscillometry), respiratory rate (f R ), sedation score immediately before and 5 minutes after treatment, and total dose of propofol required. Differences in pulse rate, MAP and propofol dose were analysed using the two-sample t -test, coughing incidence was analysed with the chi-square test, and differences in sedation score were analysed with the Mann–Whitney test. Results After treatment, the incidence of coughing at endotracheal intubation was significantly reduced in group L compared with group S (21% versus 45%; p =0.022). There was no significant difference between the groups with regard to propofol dose required for endotracheal intubation ( p =0.122), PR ( p =0.611), MAP ( p =0.508) or sedation score ( p =0.051). Conclusions and clinical relevance IV lidocaine can decrease the incidence of cough during endotracheal intubation in dogs premedicated with acepromazine and methadone, but does not appear to have a sparing effect on the dose of propofol required for endotracheal intubation. Use of IV lidocaine, prior to induction of anaesthesia with propofol may be beneficial in dogs where coughing at intubation would be detrimental.