Differential pressor response to intravenous ephedrine during recovery from deliberate hypotension.

Abstract Study objective To determine whether nitroglycerin or trimethaphan alters pressor response to intravenous (IV) ephedrine. Design Prospective, randomized study. Setting Operating room of a university hospital. Patients 60 ASA physical status I female patients scheduled for mastectomy. Interventions Patients were assigned to one of six groups (n = 10 in each). Group 1: nitroglycerin + normal saline (NS) IV, Group 2: nitroglycerin + ephedrine 0.1 mg/kg IV, Group 3: nitroglycerin + ephedrine 0.15 mg/kg IV, Group 4: trimethaphan + NS IV, Group 5: trimethaphan + ephedrine 0.1 mg/kg IV, and Group 6: trimethaphan + ephedrine 0.15 mg/kg IV. Measurements Hemodynamic responses to ephedrine following withdrawal of vasodilators were observed for 15 minutes. Main results Ephedrine increased heart rate and mean blood pressure. After ephedrine 0.1 mg/kg IV, the maximum pressor response in the trimethaphan group was approximately twofold that of the nitroglycerin group ( p = 0.038). Conclusions Ephedrine restored BP more easily in those patients who had received trimethaphan compared with those who had received nitroglycerin for deliberate hypotension.