Abstract: AIM: To compare the time-course of relaxant effect of rocuronium in Acetylcholine receptors (AchR) antibody seropositive and seronegative patients with myasthenia gravis(MG). METHODS: Twenty ASAⅠorⅡMG patients with both sexes, aged 23-59 years, with body mass index of 18-25 kg/m²,scheduled for elective extended thymectomy,were divided into 2 groups according to AChR antibody test: seropositive group (group P, n=10) and seronegative group (group N, n=10).Aesthesia was induced with iv injection of fentanyl 2 μg/kg,midazolam 0.05 mg/kg, and propofol 1.5 mg/kg.All patients were tracheal intubated and mechanically ventilated. Twitch tension was monitored in the adductor pollicis muscle by train-of-four stimulation of the ulnar nerve(intensity 60 mA,interval 12s,frequency 2 Hz, wave length 0.2 ms). Rocuronium 0.6 mg/kg was injected intravenously after calibration. The onset time of muscle relaxation,and time for T₁ to recover to 25%,time for T₁ to recover to 50% and recovery index were recorded.The heart rate variability (HRV) was analyzed during the surgery.RESULTS: There were no significant changes in MAP, HR, HRV, LF/HF ratio at all time in two groups(P>0.05). Compared with group N, there was no significant change in the onset time of muscle relaxation,and the time for T₁ to recover to 25%,time for T₁ to recover to 50% and recovery index were significantly prolonged in group P(P<0.05).CONCLUSION: The duration of rocuronium-induced neuromuscular block is significantly longer in seropositive patients with MG than seronegative,while the onset time is similar between the two groups.

Key words: androstanols, myasthenia gravis, acetylcholine receptors antibody, neuromuscular blockade, heart rate variability