Objective To observe the
histamine release and haemodynamic changes after intravenous bolus of different doses of 4 kinds
of intermediate-acting muscle relaxants. The neuromuscular blocking effects and intubation conditions were also observed. Methods Fifty one ASA I -Ⅱ patients undergoing elective surgery were divided into 7 groups which received a single bolus of different doses of vecuronium, ci-satracurium , rocuronium and atracurium respectively. Anesthesia was induced with midazolam, etomidate and fentanyl. The neuromuscular blocking effect was monitored with a Biometer accelograph, Train-of-four (TOF) stimulation was applied to the ulnar nerve at the wrist. Venous blood samples were obtained before administration of relaxant and at 2 and 5min after administration of relaxant for determination of plasma histamine concentrations using fluorometry. The haemodynamic changes before and 1-5min after administration of relaxant were also recorded. Results The plasma histamine concentrations and haemodynamic changes before and after administration of relaxant had no significant differences in 7 groups (P >0.05). The maximum block effect and condition of intubation had no significant differences in 7 groups. The onset time of Vec I was similar to that of Vec Ⅱ , but the onset time of Cis Ⅱ and Cis Ⅲ was significantly shorter than that of Cis I and Atr ( P < 0. 05 ) . The onset time of Roc was the shortest in 7 groups ( P < 0. 05 ) . Conclusion There was no significant changes neither in plasma histamine concentration nor in
haemodynamics after injection of doses of 2×ED95 of 4 kinds of muscle relaxants.