To identify the dose of rocuronium that will prevent a laryngeal response to water spraying of the glottis in anesthetized cats.Study design
Randomized crossover study.Animals
Eight healthy, adult, short-haired cats, aged 1–4 years, weighing 3.2–6.0 kg.Methods
Each cat was anesthetized four times and administered one of four doses of rocuronium (0.1, 0.2, 0.3 and 0.6 mg kg−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 (0.2 mL) 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 5 minutes) was recorded for each treatment.Results
Compared with baseline, rocuronium 0.3 mg kg−1 and 0.6 mg kg−1 significantly decreased all glottal scores obtained from the videos (all p < 0.03). Both observers gave lower VAS scores after 0.3 mg kg−1 (both p = 0.015). Apnea lasting ≥ 5 minutes occurred in none, one, three and seven of eight cats administered doses of rocuronium 0.1, 0.2, 0.3 and 0.6 mg kg−1, respectively.Conclusions and clinical relevance
Rocuronium 0.3 mg kg−1 and 0.6 mg kg−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 0.3 mg kg−1 may be useful for facilitating tracheal intubation. Positive pressure ventilation must be available for cats administered rocuronium.