• H Kirkegaard-Nielsen, H S Helbo-Hansen, P Lindholm, I K Severinsen, and K Bülow.
• Department of Anaesthesia and Intensive Care, Odense University Hospital, Denmark.
• J Clin Anesth. 1995 Dec 1;7(8):635-9.

Study Objective(1) To determine the time to peak effect of neostigmine (time to peak antagonism) during atracurium- or vecuronium-induced neuromuscular block; and (2) to determine the effect on time to peak effect of neostigmine during atracurium-induced neuromuscular block, when the dose of neostigmine is increased from 35 micrograms/kg to 70 micrograms/kg.DesignProspective, randomized clinical study.SettingGynecologic operating room suite at a university hospital.Patients45 ASA I and II women admitted for gynecologic laparotomy.InterventionsAnesthesia was performed with thiopental sodium, fentanyl, halothane, nitrous oxide, and atracurium or vecuronium. Train-of-four (TOF) stimulation and mechanomyography were used to monitor neuromuscular transmission. Neostigmine was administered while a constant degree of neuromuscular block was maintained at a twitch height at a point between 4% and 11% of the control twitch height, using a continuous infusion of atracurium or vecuronium. The patients were randomized to three groups, with 15 patients in each group. Group 1 received atracurium block antagonized with neostigmine 35 micrograms/kg; group 2 received vecuronium block antagonized with neostigmine 35 micrograms/kg; and group 3 received atracurium block antagonized with neostigmine 70 micrograms/kg.Measurements And Main ResultsThe degree of neuromuscular block at antagonism was similar in the three groups. Time to peak effect (mean +/- SD) on TOF ratio was significantly longer in Group 1 (9.7 +/- 3.0 minutes) versus Group 2 (6.6 +/- 1.4 minutes; (p < 0.05). The time to peak effect on TOF ratio during atracurium-induced block was reduced from 9.7 +/- 3.0 minutes to 6.3 +/- 2.0 minutes when the dose of neostigmine was increased from 35 micrograms/kg to 70 micrograms/kg (p < 0.05). The peak effect on TOF ratio was significantly greater in Group 3 compared with Group 1 (p < 0.05), while it was similar in groups 1 and 2.ConclusionThe time to peak effect of neostigmine 35 micrograms/kg is about 6 to 10 minutes when antagonizing a constant degree of atracurium- or vecuronium-induced neuromuscular block at a twitch height at a point between 4% and 11%. Even though the time to peak effect was longer with atracurium than with vecuronium, clinically significant differences between the antagonizing effect of atracurium versus vecuronium block were not demonstrated. The time to peak effect during atracurium-induced block decreased when the dose of neostigmine was increased from 35 micrograms/kg to 70 micrograms/kg.

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