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This Month in Anesthesiology  |   July 2001
Influence of Thoracic Epidural Anesthesia on Arrhythmias Explored in a Canine Model.
Article Information
This Month in Anesthesiology
This Month in Anesthesiology   |   July 2001
Influence of Thoracic Epidural Anesthesia on Arrhythmias Explored in a Canine Model.
Anesthesiology 7 2001, Vol.95, 6A. doi:
Anesthesiology 7 2001, Vol.95, 6A. doi:
Influence of Thoracic Epidural Anesthesia on Arrhythmias Explored in a Canine Model. Meissner et al. (page 132)
Meissner et al.  used monophasic action potential (MAP) recording, a technique that permits simultaneous measurement of cardiac action potential duration and effective refractory period, in awake mongrel dogs to elucidate the possible protective effect of thoracic epidural anesthesia (TEA) against arrhythmias mediated by enhanced adrenergic tone. MAP electrodes were implanted in the right hearts of seven dogs. After their recovery, epidural catheters were inserted during a separate procedure. After baseline electrocardiographic measurements had been obtained, the team performed unipolar cathodal pacing using the MAP catheters for stimulation to establish pacing thresholds, the data for which were digitized and stored on disk. Effective refractory periods were determined after 1 min of ventricular stimulation at a cycle length of 400 ms. Beginning at the eighth beat, a ventricular extrastimulus was introduced and increased or decreased incrementally until capture was lost on two consecutive occasions.
Subsequent to all baseline measurements, TEA was induced by injection of 0.4 mg/kg lidocaine. Autonomic nervous system blockade was performed by simultaneously injecting propranolol and hexamethonium. Programmed ventricular stimulation was used to determine local right ventricular refractory periods and MAP duration simultaneously. Atrial pacing thresholds ranged from 0.8 to 5.0 mA at cycle lengths from 200 to 400 ms. TEA increased right ventricular MAP-90 over the entire range of steady-state cycle lengths. Changes in action potential duration were paralleled by a prolongation of effective refractory period at higher rates, so that effective refractory period/action potential duration was unaffected. These results suggest that there may be a protective role of TEA against generation of ventricular arrhythmias during anesthesia. The benefits of TEA may be stronger at the ventricular as opposed to the atrial site, which showed only a trend toward prolongation of repolarization even at short cycle lengths.