• L A Fernandes, R G Stout, D G Silverman, and S J Brull.
• Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520-8051, USA.
• J Clin Anesth. 1997 Feb 1;9(1):48-51.

Study ObjectiveTo determine if posttetanic twitch following 100-Hz tetanic stimulation enables titration of a nondepolarizing relaxant infusion to a greater depth of block than that achieved with posttetanic twitch following 50 Hz.Study DesignProspective, observational study.SettingOperating rooms of a university tertiary care center.Patients10 ASA physical status II and III patients free of known neuromuscular disease and undergoing general endotracheal anesthesia for routine elective surgery.InterventionsFollowing induction of general anesthesia, neuromuscular block was maintained with a continuous intravenous vecuronium infusion. Depth of neuromuscular block was assessed by tactile evaluation of the evoked responses of the adductor pollicis muscle following supramaximal stimulation of the ulnar nerve via surface electrodes. The vecuronium infusion was titrated to loss of posttetanic twitch following 100-Hz tetanic stimulation, at which point the infusion was discontinued.Measurements And Main Results100-Hz tetanic stimulation was repeated every two minutes until recovery of the first posttetanic twitch, at which point 50-Hz tetanic stimulation was repeated every two minutes until recovery of the first posttetanic twitch. The median time (interquartile range) from discontinuation of the vecuronium infusion to recovery of the first posttetanic twitch following 100-Hz tetanic stimulation was 27% faster than the corresponding time to recovery of the first posttetanic twitch following 50-Hz tetanic stimulation [19 (10 to 24) min and 26 (20 to 30) min respectively, p < 0.002].ConclusionsPosttetanic twitch following 100-Hz tetanic stimulation enables titration of a vecuronium infusion to a greater depth of block than posttetanic twitch following 50-Hz tetanic stimulation. The present findings should enable more effective titration of this relaxant, thereby reducing the likelihood of unwanted patient movement or unduly prolonged recovery due to relaxant overdosing.

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