Haemodynamic interaction of high‐dose fentanyl and increasing doses of vecuronium in patients undergoing myocardial revascularization

Background. Bradyarrhythmia has been reported with vecuronium when given with high dose narcotics. We hypothesized that if the bradycardic response is dependent on a vagal reaction mediated by narcotics, it should be independent of the vecuronium dose. A dose‐related response of vecuronium on heart rate (HR) would be in favour of a chronotropic action of this agent.Methods. We examined three induction techniques using high doses of fentanyl in which vecuronium was given in increasing doses. In addition, a reference group received a low dose of atracurium. Forty patients scheduled for elective CABG surgery were anaesthetized with fentanyl (50 μg) given over 5 min, and were randomly assigned to receive either 0.056, 0.14, 0.28 mg/kg of vecuronium or 0.28 mg/kg of atracurium. Haemodynamic measurements were obtained at the following intervals: before induction (time 0), after the administration of fentanyl (at 5 min), and 1, 2 and 5 min after tracheal intubation (at 10, 11 and 15 min).Results. In vecuronium‐treated groups, there were significant decreases in HR, mean arterial pressure, and cardiac output (P<0.05). There were no differences between the three vecuronium groups. Although the atracurium‐treated group displayed no significant haemodynamic changes, 2 patients of this group developed HR < 40 bpm.Conclusions. Over the range of vecuronium doses studied, we observed a reduction in HR during induction for CABG surgery with high doses of fentanyl and vecuronium. This effect was not dose dependent and is likely related to a direct effect of a high‐dose narcotic technique and/or due to a vagal stimulation regarding the airway procedure.