[Circulatory effects of vecuronium as well as pancuronium under different conditions of anesthesia]

The cardiovascular effects of equipotent doses (1,25 X ED95) of vecuronium (70 micrograms/kg iv) and pancuronium (80 micrograms/kg iv) were studied in 16 patients scheduled for elective coronary artery bypass surgery during steady-state conditions of isoflurane (0,4-0,5 vol% end-tidal)-nitrous oxide anaesthesia. All patients were chronically treated with oral beta receptor-blocking agents. Vecuronium did not cause any significant cardiovascular changes whereas pancuronium produced increases in heart rate (13%), cardiac index (15%) and mean arterial pressure (4%) while systemic vascular resistance decreased (8%). In a second part of this study we analysed whether the magnitude of the vagolytic effects of pancuronium is influenced by the anaesthetic procedure and/or by preoperative beta-blocker therapy. A group of 8 patients who were pretreated with beta-receptor blockers and received fentanyl (7 micrograms/kg) during the anaesthetic procedure showed low control values of heart rate (HR), cardiac index (CI), mean arterial pressure (MAP) and the rate-pressure product (RPP) which were due to both, the antisympathetic effects of beta-blocker therapy and the central vagomimetic properties of fentanyl. The administration of pancuronium (80 micrograms/kg) caused the greatest percentage increases in HR (20%), CI (22%), MAP (8%) and RPP (31%) in this group of patients. In contrast, patients (n = 8) anaesthetized with isoflurane-nitrous oxide who were not on preoperative beta-receptor blocker medication, demonstrated higher haemodynamic control values and less increases in HR (10%), CI (10%) and RPP (15%), MAP did not change. The clinical significance of these findings is discussed.