[Differences in the neuromuscular blockade of the larynx and thenar muscles following relaxation with vecuronium].

To objectivate the clinical impression of different neuromuscular depression in the larynx- and limb-musculature, an attempt was made in 5 patients to quantify laryngeal muscle relaxation by electromyographic recordings of evoked responses from the vocalis muscle during endolaryngeal microsurgery. Mechanographic and evoked electromyographic recordings of the thenar muscles were obtained simultaneously. Nearly total suppression of evoked responses at the peripheral muscle site was observed after a bolus dose of either 60 micrograms/kg or 100 micrograms/kg of the nondepolarising muscle relaxant Vecuronium. However, the vocalis muscle was not blocked completely. The neuromuscular depression ranged from 61 to 92% depending on the dose. In no case was the recommended intubating dose (ED 95) of 60 micrograms/kg sufficient for complete relaxation of the vocalis muscle. The present results do not support that the extent and/or time course of intrinsic laryngeal muscle relaxation correlates with peripheral neuromuscular depression in a quantitative manner. The different degree of relaxation achieved by Vecuronium in the hand and larynx is probably due to their different content of acetylcholine receptors.