Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. II. Effects of enflurane and isoflurane during exposure to epinephrine with and without muscarinic blockade.

摘要: BACKGROUND Atrial dysrhythmias precede ventricular during epinephrine-anesthetic sensitization, and may be caused by an altered relationship between automaticity of primary subsidiary pacemakers. The following hypotheses were tested: (1) epinephrine-induced pacemaker shifts with enflurane or isoflurane require intact vagal reflexes (2) these anesthetics sensitize the atrial myocardium to dysrhythmias. METHODS Eight dogs instrumented for chronic electrophysiologic investigation, including electrodes at SA node, appendages, right ventricle, His bundle, along sulcus terminalis. After conscious-state testing, anesthetized exposed epinephrine, without atropine methylnitrate. Eight-channel ECG recordings analyzed before epinephrine infusions. pacemakers assigned values 1-6 increasing distance from normalized expressed as site earliest activation value (SEA). RESULTS Epinephrine increased SEA anesthesia. Atropine enhanced this increase anesthesia, but abolished Enflurane only when combined atropine. Isoflurane did not under any test conditions. CONCLUSIONS With enflurane, in chronically are direct depression node a relative isoflurane, reflex-induced suppression escape latent sensitizes muscarinic blockade; does atrium.