A priming technique accelerates onset of neuromuscular blockade at the laryngeal adductor muscles.

Purpose: Priming is a known technique to accelerate onset of neuromuscular blockade (NMB). Its effect on NMB of the larynx has not been studied yet.

Methods: We compared a priming technique with a bolus application of rocuronium on the onset of NMB at the laryngeal adductor and the adductor pollicis muscles (AP). In 30 female patients, after induction of anesthesia a tube with a surface electrode was placed into the trachea prior to the administration of any neuromuscular blocking agent to monitor electromyography (EMG) of the laryngeal adductor muscles. Neuromuscular monitoring consisted of EMG of the laryngeal adductor muscles and the left AP. Patients were randomized into two groups. After transcutaneous stimulation of the recurrent laryngeal nerve and ulnar nerve, a bolus of rocuronium 0.6 mg x kg(-1) (Bolus group) or a priming dose of rocuronium 0.06 mg x kg(-1) followed by rocuronium 0.54 mg x kg(-1) three minutes later (Priming group) were injected. Lag time, onset 90%, onset time and peak effect of NMB were recorded and compared; a P < 0.05 was considered significant.

Results: The onset 90% and onset time measured at the laryngeal adductor muscles (onset: 44.7 +/- 7.4 vs 74.0 +/- 23.8 sec) and at the AP (onset: 105.4 +/- 29.9 vs 139.2 +/- 51.5 sec) were significantly shorter in the Priming group than in the Bolus group. Within groups, the onset times were significantly shorter at the laryngeal muscles in comparison to AP.

Conclusion: Our results indicate that a priming technique with rocuronium significantly accelerates the onset of NMB at the laryngeal adductor muscles. Our results further support the use of rocuronium as an alternative to succinylcholine for rapid sequence induction.