EFFECT OF TETANIC STIMULATION ON SUBSEQUENT TRAIN-OF-4 RESPONSES SAT VARIOUS LEVELS OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCK

Tetanic stimulation influences subsequent neuromuscular responses. In addition, the tetanus-induced changes in neuromuscular responses diffe r according to the level of neuromuscular block at which tetanic stimu lation is delivered. We studied the tetanus-induced effect on subseque nt train-of-four (TOF) responses at various levels of vecuronium-induc ed neuromuscular block in 45 anaesthetized patients. Tetanic stimulati on was applied when a twitch height of T1 returned to 25%, 50% and 75% of its control twitch height (T0) (groups 1, 2 and 3, respectively) a fter administration of vecuronium 0.1 mg kg(-1). Maximum posttetanic p ercentage increases in TOF responses in groups 1,2 and 3 were 257 (SD 119)%, 107 (75)% and 68 (54)% for T1/T0 (P < 0.001 for group 1 vs 2; P < 0.001 for group 1 vs 3) and 535 (259)%, 421 (213)% and 292 (171)% f or T4/T1 (P < 0.01 for group 1 vs 3), respectively. Durations of postt etanic increases in TOF responses in groups 1, 2, and 3 were 52 (19) s , 37 (14) s and 32 (13) s for T1/T0 (P < 0.05 for group 1 vs 2; P < 0. 01 for group 1 vs 3) and 53 (17) s, 46 (15) s and 35 (12) s for T4/T1 (P < 0.05 for group 1 vs 3), respectively. These data suggest that the tetanus-induced effect on subsequent TOF is more apparent and lasts l onger at greater degrees than at lesser degrees of neuromuscular block .