Infusion of vecuronium assessed by tactile evaluation of evoked thumb twitch.

In 15 patients (ASA I-II) undergoing intraabdominal gynaecological surgery, muscle paralysis for tracheal intubation and surgery was achieved by a combined bolus and demand infusion of vecuronium. The initial loading dose of 67 micrograms kg-1 and the rate of subsequent infusion were determined by evaluation of the tactile twitch response to train-of-four (TOF) stimulation of the ulnar nerve while the neuromuscular blockade obtained was recorded blindly for control on the contralateral arm. A maintenance dose of 4.9 mg h-1 (2.0-7.6 mg h-1) produced a smooth course of blockade with minimum and maximum values of twitch height during infusion of 2% and 12%, respectively. A period of 15.9 min elapsed from the end of infusion to a TOF-ratio of 0.7, when neostigmine 2.5 mg was administered at the point of two palpable twitches to TOF-stimulation. Simple tactile evaluation of peripheral nerve stimulation is sufficient to determine the infusion rate of vecuronium required to produce stable and appropriate neuromuscular blockade during intra-abdominal surgery.