Objective To evaluate the effects of different storage periods at room temperature on domestic cisatracurium-induced neuromuscular (N-M) block.Methods One hundred and twenty ASA Ⅰ or Ⅱ patients,aged 18-64 yr,scheduled for elective operations under general anesthesia,were randomly divided into 3 groups (n =40 each):cisatracurium stored for 60 days at 4-8 ℃ group (group LT),cisatracurium stored for 30 days at room temperature group (group RT30) and cisatracurium stored for 60 days at room temperature group (group RT60).Anesthesia was induced with iv injection of midazolam and target-controlled infusion of propofol (target plasma concentration 3 μg/ml) and remifentanil (target effect-site concentration 3-5 ng/ml).A bolus of cisatracurium 0.2 mg/kg was given intravenously over 5-10 s as soon as the patients lost consciousness.N-M block was monitored with TOF-Watch SX (Organon,Netherlands).Single stimulation was applied to the ulnar nerve at wrist.The maximal degree of N-M block,onset time,clinical duration,recovery index and 75 % recovery time were recorded.The patients were intubated and mechanically ventilated when N-M block reached the maximal degree.The intubation condition was evaluated.Hypotension,bradycardia and skin allergy were recoded.Results Compared with group LT,no significant change was found in the onset time,clinical duration,recovery index and 75% recovery time in group RT30 (P > 0.05),and the onset time was significantly prolonged,clinical duration and 75% recovery time were shortened in group RT60 (P < 0.05).The onset time was significantly longer and clinical duration was shorter in group RT60 than in group RT30 (P < 0.05).The intubation condition was excellent or good in the three groups and there was no significant difference among the three groups.There was no significant difference in the incidence of hypotension and bradycardia among the three groups (P > 0.05).No patients developed skin allergy.The maximal degree of N-M block was 100% in groups LT,RT30 and RT60 except one case with 95% in group RT60.Conclusion No significant change is found in the N-M block induced by domestic cistracurium when stored for 30 days at room temperature,however,the N-M block is significantly attenuated when stored for 60 days at room temperature. Key words: Atracurium; Neuromuscular blockade; Temperature; Time factors