Onset and Duration of Succinylcholine and Vecuronium Neuromuscular Blockade at Laryngeal Adductor and Adductor Pollicis Muscles

Hwang, Seung Ok; Kim, Seok Kon; Park, Nam Hoon

Abstract

Adequate relaxation of the laryngeal adductor muscle is required to obtain good tracheal intubating condition. But we couldnt check rountinely laryngeal adductor muscle response, so we quantify the effects of succinylcholine and vecuronium at the laryngeal adductor muscles and the adductor pollicis. Twenty adult patients of ASA physical status 1-2 were studied during propofol-fentanyl anesthesia. The trachea was intubated without the use of muscle relaxants and the tube cuff placed between the vocal cords. Succinylcholine 1.5 mg/kg or vecuronium 0.1 mg/kg was given as a single bolus by random allocation. Muscular activity was evoked with supramaximal stimuli in a train-of-four sequence every 12 sec to the ulnar nerve and the anterior branch of the recurrent laryngeal nerve at the notch of the thyroid cartilage and forehead. Neuromuscular transmission was monitored at wrist by mechano-myography and laryngeal response was measured as pressure changes in the cuff of the tracheal tube positioned between the vocal cords. Pressure inside the cuff was measured with an air-filled transducer. TOF responses of both sites were continuously recorded on strip chart. Lag time and onset time were no statistically significant differences at the laryngeal adductor and adductor pollicis after succinylcholine or vecuronium bolus injection. Clinical durations were significantly shorter at the laryngeal adductor than at the adductor pollicis after succinylcholine and vecuronium injection. In one patient, onset of neuromuscular blocking effect with vecuronium was 125 sec slower at the laryngeal adductor than at the adductor pollicis. We recommand that if vecuronium is selected for gentle and smooth tracheal intubation, intubation will be delayed sufficient time after adductor pollicis relaxation.