BACKGROUND: This study was designed to evaluate the hemodynamic effects of vecuronium, pancuronium and rocuronium in patients with coronary artery disease (CABG) or valvular heart disease (VHD). METHODS: With IRB approval, 121 patients (61 patients with CABG and 60 patients with VHD) were randomly divided into a vecuronium, pancuronium and rocuronium group, respectively. Midazolam and fentanyl were administered and then 3 times of ED95 of a muscle relaxant (vecuronium, 0.12 mg/kg; pancuronium, 0.12 mg/kg; or rocuronium, 0.9 mg/kg) was injected. Additional dose of fentanyl was given and the patient was intubated. Hemodynamic variables were measured before the induction of anesthesia, just prior and 1 min after the administration of the muscle relaxant, just before intubation, 5 and 10 min after intubation. RESULTS: The number of patients enrolled in the CABG-vecuronium, CABG-pancuronium, CABG- rocuronium, VHD-vecuronium, VHD-pancuronium, and VHD-rocuronium was 20, 20, 21, 19, 20, and 21 respectively. Each of 10, 4, 4, 5, 1, and 1, respectively, were treated for hypotension or bradycardia during the induction of anesthesia. The heart rate (HR) changed significantly only in the CABG- vecuronium group compared with the control value. All three muscle relaxants decreased mean systemic artery pressure (MAP) significantly in both CABG and VHD patients. The decrease in HR and MAP were significantly greater in CABG-vecuronium and VHD-vecuronium than in CABG-pancuronium and VHD-pancuronium, respectively. The decrease in HR was also greater in VHD-vecuronium than in VHD-rocuronium. Cardiac index (CI) decreased in CABG-vecuronium and all VHD patients. The decrease in CI was greater in CABG-vecuronium than in CABG-pancuronium but it was not significantly different among the three muscle relaxants in VHD patients. CONCLUSIONS: While pancuronium and rocuronium exerted minimal hemodynamic effects, vecuronium reduced HR and MAP more significantly than pancuronium in both CABG and VHD patients, and CI also decreased more significantly with vecuronium in CABG patients.