BACKGREOUND: Several studies have demonstrated that atracurium produced cardiovascular response by releasing histamine but cis-atracurium has no any singnificant cardiovascular effect. However, evaluation of hemodynamic response of atracurium or cis-atracurium by using TEE has not yet to be reported. Accordingly, we evaluated the effect of atracurium or cis-atracurium on the left ventricular function of surgical patients using TEE. METHODS: Twenty adult patients were studied. Patients were intubated with thiopental sodium (4mg/kg), fentanyl (100 microgram) and succinylcholine (1.5 mg/kg) and anesthesia was maintained with enflurane (0.8%) and nitrous oxide (50%) and oxygen (50%). The patients were randomly assigned to give the neuromuscular blocking equipotent (2 x ED95) doses of atracurium or cis-atracurium. The transesophageal echocardiographic probe was inserted properly to measure the end-diastolic diameter, end-systolic diameter, end-diastolic area and end-systolic area. The stroke volume index (SVI), cardiac index (CI), ejection fraction (EF), fractional shortening (FS), and fractional area change (FAC) were calculated. Heart rate (HR) and mean arterial pressures (MAP) were recorded and all data were collected just before, and 1, 2, 3, 5 and 10 minutes after injection of atracurium (0.5 mg/kg) or cis-atracurium (0.1 mg/kg). RESULTS: The MAP, SVI, CI, EF, FS, and FAC did not show any statistically significant changes after the drug administration in either groups and did not show any statistically significant difference between the two groups when compared at same time points. HR at 5 and 10 minutes after injection of cis- atracurium is significantly decreased than the control. CONCLUSIONS: Two times of ED95 dose of atracurium or cis-atracurium had no significant effects on left ventricular function in healthy adult patients during the general anesthesia with N2O-enflurane.