COMPARATIVE RECOVERY OF 50-HZ AND 100-HZ POSTTETANIC TWITCH FOLLOWINGPROFOUND NEUROMUSCULAR BLOCK

Study Objective: To determine if posttetanic twitch following 100-Hz t etanic stimulation enables titration of a nondepolarizing relaxant inf usion to a greater depth of block than that achieved with posttetanic twitch following 50 Hz. Study Design: Prospective, observational study . Setting: Operating rooms of a university tertiary care center. Patie nts: 10 ASA physical status II and III patients free of known neuromus cular disease and undergoing general endotracheal anesthesia for routi ne elective surgery. Interventions: Following induction of general ane sthesia, neuromuscular block was maintained with a continuous intraven ous vecuronium infusion. Depth of neuromuscular block was assessed by tactile evaluation of the evoked responses of the adductor pollicis mu scle following supramaximal stimulation of the ulnar nerve via surface electrodes. The vecuronium infusion was titrated to loss of posttetan ic twitch following 100-Hz tetanic stimulation at which point the infu sion was discontinued. Measurements and Main Results: 100-Hz tetanic s timulation was repeated every two minutes until recovery of the first posttetanic twitch, at which point 50-Hz tetanic stimulation was repea ted every two minutes until recovery of the first posttetanic twitch. The median time (interquartile range) from discontinuation of the vecu ronium 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 TO-Hz tetanic st imulation [19 (10 to 24) min and 26 (20 to 30) min respectively, p < 0 .002]. Conclusions: Posttetanic twitch following 100-Hz tetanic stimul ation enables titration of a vecuronium infusion to a greater depth of block than posttetanic twitch following 50-Hz tetanic stimulation. Th e present findings should enable more effective titration of this rela xant, thereby reducing the likelihood of unwanted patient movement or unduly prolonged recovery due to relaxant overdosing. (C) 1997 Elsevie r Science Inc.