Efficacy of lidocaine hydrochloride for laryngeal desensitization: a clinical comparison of techniques in the cat.

Assessment of laryngeal relaxation and ease of intubation in cats was made after preanesthetic medication with acepromazine/meperidine/atropine (IM) and induction of anesthesia 20 minutes later by thiopental administration (IV). Healthy cats (n = 32) scheduled for elective surgery were randomly assigned to 1 of 4 treatment groups to be provided with laryngeal desensitization: group 1, 2% lidocaine HCl (2 mg/kg of body weight) given IV 30 seconds before thiopental induction; group 2, 2% lidocaine HCl (2 mg/kg) topically applied to the larynx; group 3, 10% lidocaine HCl (10 mg) as a topical aerosol; and group 4, no treatment before intubation. A significant (P less than 0.05; ANOVA) difference between groups in the reaction to intubation attempts was apparent. Cats receiving 2% lidocaine IV or no treatment for desensitization had a greater response to intubation than did those receiving 2% or 10% lidocaine topically. The number of attempts required to intubate cats was significantly (P less than 0.05) greater in cats with no treatment than in cats treated topically with 2% or 10% lidocaine. Response to IV administration of 2% lidocaine HCl was not significantly different from the response to other treatments, indicating little advantage over no laryngeal desensitization. It was concluded that topical application of 2% lidocaine (2 mg/kg) or 10% lidocaine aerosol 1 1/2 minutes before intubation provides effective laryngeal desensitization in the cat.