Prevention of laryngospasm with rocuronium in cats: a dose-finding study

ObjectiveTo identify the dose of rocuronium that will prevent a laryngeal response to water spraying of the glottis in anesthetized cats. Study designRandomized crossover study. AnimalsEight healthy, adult, short-haired cats, aged 1-4years, weighing 3.2-6.0kg. MethodsEach cat was anesthetized four times and administered one of four doses of rocuronium (0.1, 0.2, 0.3 and 0.6mgkg(-1)) in random order. The larynx was observed with a video-endoscope inserted through a laryngeal mask airway. Video-clips of the laryngeal response to a sterile water spray (0.2mL) were obtained at baseline (without rocuronium) and at maximal effect of each treatment. Glottal closure score (0-2), duration of glottal closure, and number of adductive arytenoid movements were obtained from video-clips of laryngeal responses (reproduced in slow motion) at baseline and after treatment. Two observers blinded to treatment allocation scored the vigor of the laryngeal response on a visual analog scale (VAS). The duration of apnea (up to 5minutes) was recorded for each treatment. ResultsCompared with baseline, rocuronium 0.3 mg kg(-1) and 0.6mgkg(-1) significantly decreased all glottal scores obtained from the videos (all p<0.03). Both observers gave lower VAS scores after 0.3mgkg(-1) (both p=0.015). Apnea lasting 5minutes occurred in none, one, three and seven of eight cats administered doses of rocuronium 0.1, 0.2, 0.3 and 0.6mgkg(-1), respectively. Conclusions and clinical relevanceRocuronium 0.3 mg kg(-1) and 0.6mgkg(-1) consistently decreased the completeness and duration of the laryngeal response to water spray, and reduced the number of arytenoid adductive movements in response to that stimulus. However, a laryngeal response was never completely prevented. Rocuronium 0.3mgkg(-1) may be useful for facilitating tracheal intubation. Positive pressure ventilation must be available for cats administered rocuronium.