AIM: Previous studies have shown that the administration of remifentanil (a mu-agonist opioid) is often accompanied by bradyarrhythmias preventable or manageable by parasympatholytic drugs. The aim of this paper is to evaluate if these negative chronotropic effects are exclusively due to an increased parasympathetic activity or to a direct action of remifentanil on heart conduction fibres. METHODS: A transesophageal pacing electrophysiological study on 40 healthy subjects scheduled for orthopaedic surgical treatment under general anaesthesia has been carried out. We determined either the correct sinus recovery time or the occurrence of Wencke-bach atrio-ventricular block in the awake state and, again, during remifentanil administration. RESULTS: In all patients either a significant depression of sino-atrial automatism or a decrease of atrio-ventricular node conduction reserve was noticed. In 2 cases, in particular, a sinus arrest and a junctional rhythm, respectively, both spontaneously recovered were observed. CONCLUSION. Atropine normalized all parameters, confirming that remifentanil-associated hypokinetic cardiac phenomena are exclusively vagally mediated.
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