Time-dependent laryngeal desensitisation following topical lidocaine and prilocaine application in cats: a randomised controlled study.

OBJECTIVES

To compare the effects of topical prilocaine and lidocaine, relative to topical 0.9% sodium chloride, on laryngeal reactivity in anaesthetised cats prior to endotracheal intubation.

MATERIALS AND

METHODS

In this prospective, randomised, controlled, double-blind study, 24 healthy adult cats were enrolled and allocated to topical prilocaine, topical lidocaine or topical 0.9% sodium chloride (n = 8/group) following anaesthesia with a standardised medetomidine-propofol protocol. The calculated volume of each local anaesthetic corresponding to 2 mg/kg, prepared from 2% stock solutions, was diluted with 0.9% sodium chloride to a standardised final volume of 0.5 mL and atomised onto the arytenoid and vocal fold regions.

RESULTS

Relative to sodium chloride, prilocaine was associated with lower laryngeal reactivity at earlier time points (15 to 45 seconds), whereas lidocaine showed a later onset (from 60 seconds onward). Between 60 and 90 seconds, both prilocaine and lidocaine resulted in lower reactivity scores than sodium chloride, and no difference was observed between prilocaine and lidocaine at any assessed time point. No clinically evident adverse events were recorded during clinical monitoring of SpO2, heart rate, respiratory pattern, mucous membrane colour and clinical signs such as local irritation, hypersalivation, vomiting, marked gagging, apnoea, desaturation, bradycardia or arrhythmia.

CLINICAL SIGNIFICANCE: Topical prilocaine and lidocaine reduced laryngeal reactivity compared with topical 0.9% sodium chloride under the conditions of this study. The observed reductions occurred within the assessed 15 to 60 seconds interval; however, intubation conditions were not evaluated as comparative outcomes, and the clinical implications should therefore be interpreted in relation to laryngeal reactivity rather than direct measures of intubation performance.