Plasma concentrations of lidocaine following laryngeal administration or laryngeal and intratesticular administration in cats

Abstract

OBJECTIVE To determine plasma concentrations of lidocaine after laryngeal administration or laryngeal and intratesticular administration in cats. ANIMALS 14 healthy adult sexually intact male cats (7 cats/treatment). PROCEDURES Cats were randomly allocated to receive 0.1 mL of 2% or 10% lidocaine hydrochloride solution (treatments L2 and L10, respectively) sprayed on the larynx for laryngeal desensitization, followed by endotracheal intubation and isoflurane anesthesia. After a 7-day washout period, cats were again randomly allocated to receive treatment L2 or L10, and castration was performed under isoflurane anesthesia following intratesticular administration of 2% lidocaine solution (0.1 mL/kg). In both experiments, a blood sample for measurement of plasma lidocaine concentration was obtained before (0 minutes) and 3, 5, 10, 15, 20, 30, 45, 60, and 75 minutes after laryngeal administration of lidocaine solution. Anesthesia was discontinued at 60 minutes. Plasma lidocaine concentrations were measured with high-performance liquid chromatography. RESULTS After treatments L2 and L10, median maximum plasma lidocaine concentrations were 34.1 ng/mL (range, 0 to 279.4 ng/mL) and 93.6 ng/mL (range, 79.3 to 182.2 ng/mL), respectively. Time to maximum plasma concentration was 10 minutes (range, 0 to 20 minutes) for each treatment. When cats received intratesticular lidocaine administration following L2 or L10 treatment, median maximum plasma concentration was 181.0 ng/mL (range, 103.7 to 600.2 ng/mL) and 301.2 ng/mL (range, 265.8 to 1,770.0 ng/mL), respectively. CONCLUSIONS AND CLINICAL RELEVANCE On the basis of these data, combined laryngeal and intratesticular administration of lidocaine solution at a total dose of approximately 5 mg/kg appears to be safe for use in healthy adult cats.

Local and regional anaesthesia in dogs and cats: Overview of concepts and drugs (Part 1)

“…However, it is not necessary to include the very small amount of lidocaine typically used on the arytenoids during intubation of cats as part of the total cumulative dose. In adult cats, 2% lidocaine dosed at 0.1 ml (total dose) administered topically on the larynx PLUS 0.1 ml/kg administered intratesticularly produced serum concentrations well below toxic levels (Soltaninejad & Vesal, 2018). In contrast, as mentioned by the reviewer of this manuscript, the dose of a specific product (not used by the authors) is up to 5 mg/kg for arytenoid desensitization.…”

Evaluation of the time to desensitization of the larynx of cats following topical lidocaine application

“…4 A 60-90 s desensitization time has also been used without complications. 2,3,6,14 As this was a clinical study, it was elected to complete the evaluation using a standardized score at the time of application of lidocaine by a trained group of veterinary professionals. However, this resulted in the evaluations being completed by personnel not blinded to the treatment group.…”

“…Laryngospasm has been reported in cats following mechanical stimulation from attempts at endotracheal intubation. [1][2][3] Strategies to reduce laryngospasm facilitate successful intubation. 4 Lidocaine 2%, 5% and 10% topically desensitized the larynx allowing easy intubation in cats.…”

“…5 Plasma concentration of lidocaine remained within safe limits when cats received 2 and 10 mg of lidocaine topically on the larynx without signs of toxicity. 3 Time to desensitization of the larynx after topical lidocaine application has been reported to be 90-120 s. 2,4 Clinical studies and guidelines suggest 60 s as a minimum time. 3,6 Clinically, most veterinary professionals may not wait 60 s before an attempt to intubate owing to time constraints and concerns about respiratory depression from induction agents and risk of aspiration.…”

“…3 Time to desensitization of the larynx after topical lidocaine application has been reported to be 90-120 s. 2,4 Clinical studies and guidelines suggest 60 s as a minimum time. 3,6 Clinically, most veterinary professionals may not wait 60 s before an attempt to intubate owing to time constraints and concerns about respiratory depression from induction agents and risk of aspiration. However, there is no evidence that suggests shorter times are effective at reducing laryngeal sensitivity to intubation.…”