Comparison of the effects of topical lignocaine spray applied before or after induction of anaesthesia on the pressor response to direct laryngoscopyand intubation

In an attempt to attenuate the cardiovascular pressor response to laryngosc opy and intubation, 30 patients presenting for routine ophthalmic surgery w ere studied and were randomly allocated into two groups: group A (n=15) rec eived direct laryngeal/tracheal lignocaine spray immediately before intubat ion; and group B (n=15) received orolaryngeal lignocaine spray before the i nduction of anaesthesia. In both groups, general anaesthesia was induced wi th thiopentone 3-5 mg kg(-1), followed by atracurium 0.6 mg kg(-1) to facil itate tracheal intubation. Laryngoscopy and endotracheal intubation caused a significant increase in heart rate, by 28% in group A and 23% in group B (P < 0.05 in both), and in diastolic blood pressure, by 28% in group A and 24% in group B (P < 0.05 in both). In group A, the systolic blood pressure also increased significantly (by 18%) after intubation, but there was no si gnificant change in group B. In addition, the plasma lignocaine concentrati ons remained well below the toxic range in both groups. It was concluded th at topical lignocaine administration as an orolaryngeal spray before the in duction of anaesthesia is effective in reducing but not abolishing the pres sor response to laryngoscopy and endotracheal intubation