Use of neuromuscular blockade with rocuronium bromide for intubation in cats

To determine whether neuromuscular blockade with rocuronium bromide (RB) would improve endotracheal intubation (EI) conditions in comparison with topical lidocaine hydrochloride (LH).

Randomized prospective study.

Forty seven healthy cats of unspecified breed, aged 17 ± 11 months and weighing 2.8 ± 0.8 kg, undergoing elective procedures.

Anesthesia was induced with xylazine (XZ) (1.1 mg kg(-1) IM) and tiletamine-zolazepam (XTZ) (7 mg kg(-1) IM) and EI was attempted. Cats which could not be intubated at the first attempt (n = 34), were randomly medicated with either 0.1 mL LH 10% spray on the laryngeal mucosa (n = 17) or 0.6 mg kg(-1) intravenous RB (n = 17). Sixty seconds later, a second attempt at EI was performed. The effect of both drugs was assessed using a previously published scale (Sandor Agoston). EI conditions associated with laryngoscopy, vocal cord position and movement, cough, patient movement, time and attempts needed in order to perform EI were recorded. Heart rate and end-expired CO2 concentration were monitored.

Groups were comparable in age, weight, gender and hematological parameters. Clinically acceptable EI conditions were not significantly different between RB and LH assisted groups (p = 0.31). However, there was a significant difference in cough, vocal cord movement and position between the RB and the LH groups. The group intubated at the first attempt and receiving neither RB nor LH coughed persistently (11/13). The cats receiving RB had to be ventilated for 10-28 minutes.

The present study shows that, when used in cats anesthetized with XTZ, RB paralyzes the internal laryngeal muscles keeping the vocal cords in an intermediate position (paramedial) 60 seconds after being administered. RB is an effective alternative to LH to overcome the airway protective reflexes when performing EI but requires ventilatory support until the paralysis wears off.