BACKGROUND: Hemodynamic changes through the histamine-induced release of atracurium are relatively common, but can be particularly dangerous in hemodynamically unstable patients. This study evaluated the effectiveness of a pretreatment with an anti-histamine agent before the administration of atracurium in the prevention of histamine-induced hemodynamic changes. METHODS: Forty-eight ASA class I and II patients were assigned to four groups. Groups 1 and 2 were assigned to receive atracurium through a bolus 0.5 mg/kg. Groups 3 and 4 were assigned to receive atracurium through a bolus 1.0 mg/kg. Group 1 and 3 were pretreated with pheniramine (H1-blocker) and ranitidine (H2-blocker) intravenously before the induction of general anesthesia. After induction, HemosonicTM 100 was installed and the following hemodynamic parameters were measured: systemic vascular resistance (SVR), cardiac index (CI), heart rate (HR) and blood pressure (BP) immediately before, 1, 2, 3, 5 and 10 min after the rapid administration of the atracurium bolus before the skin incision. RESULTS: Groups 1 and 3 showed more stable hemodynamics than groups 2 and 4. Group 2 showed more significant changes in the SVR, CI, BP, HR than group 1 (P< 0.05). Group 4 showed more significant changes in the SVR, CI, BP, HR than group 3, and some cases were significant hemodynamically (P< 0.05). Group 4 showed more significant changes in the SVR, CI, BP, HR than group 2 (P <0.05). CONCLUSIONS: Pretreatment with an anti-histamine drug prior to the administration of atracurium can be effective in attenuating the hemodynamic responses.