Median effective dose of cisatracurium priming accelerating onset of neuromuscular block in patients of different genders

Objective To investigate the median effective dose (ED50) of cisatracurium priming accelerating the onset of neuromuscular block in patients of different genders. Methods Ninety ASA Ⅰ or Ⅱ patients aged 18-55 yr undergoing elective abdominal operation under general anesthesia were divided into 2 groups ( n = 45 each): male group (group M) and female group (group F). Neuromuscular block was monitored with accelerograph F (TOF-Watch SX). A single twitch stimulation of ulnar nerve was used to monitor neuromuscular function.Anesthesia was induced with midazolam 0.04 mg/kg and fentanyl 1 μg/kg. Accelerograph F was opened after the patients lost consciousness. The priming dose of cisatracurium was injected intravenously, then fentanyl 5 μg/kg and propofol 2 mg/kg were injected intravenously 3 min later and the left dose of cisatracurium for intubation was injected intravenously 4 min later. Tracheal intubation was performed when the ratio of the single twitch stimulation value to control value (T/Tc). decreased to 10%. Anesthesia was maintained with iv infusion of propofol and remifentanil and inhalation of isoflurane. The priming dose of cisatracurium was determined by up-and-down sequential trial. The initial priming dose was set at 5 μg/kg. The ratio of two successive doses was 1.2. T/Tc, time to 90% block, onset time, maximal neuromuscular block and clinical duration were recorded 4 min after the administration of the priming dose. The ED50 and 95% confidence interval (CI) of cisatracurium priming required to accelerate the onset were caculated. Results Time to 90% block was significantly longer-in group M than in group F (P ＜0.05). No significant difference was found in the other parameters among the groups. The ED50 and 95% CI of cisatracurium priming required to accelerate the onset were 21.36 μg/kg (95% CI 20.52-22.23 μg/kg)in group M and 14.53 μg/kg (95% CI 13.77-15.33 μg/kg) in group F. The ED50 was significantly higher in group M than in group F ( P ＜ 0.05). Conclusion The ED50 of cisatracurium priming accelerating thd onset is 21.36 and 14.53 μg/kg in male and female respectively and it is significantly higher in male than in female. Key words: Atracurium; Sex factrs; Dose-response relationship,drug