Elective countershock in unanesthetized patients with use of an esophageal electrode.
CONSIDERABLE attention has recently been shown in dispensing with general anesthesia during countershock.1-4 This problem has also interested us and the present report deals with our attempt at solving it by using an esophageal electrode. Only a fraction of the energy administered to the patient during countershock by the usual, surface electrode technic is usefully consumed within the heart. The remainder is dissipated elsewhere, in driving current not only to and from the heart, but through pathways that circumvent it entirely. The distribution of electrical energy among these fractions is determined by the location of the electrodes on the chest and by the spatial configuration of the varyingly resistive tissues of the thorax. When electrodes are applied directly to the heart, depolarization is achieved with about 5 watt-seconds of energy5; in clinical external countershock, even with optimal electrode placement and a good subject, energies of 50 watt-seconds or more are almost always necessary. Thus, the greater part by far of the administered energy is expended in extracardiac tissues where, since it does not participate in depolarizing the heart, it is wasted. Clinical external countershock is, then, at best an operation of appreciably low efficiency. The relevance of these considerations to the problem of avoiding the need for anesthesia 124 is that it is precisely that fraction which is dissipated outside the heart which gives rise to the discomfort of countershock: it is current flow in tissues other than the heart-principally in skeletal muscles-and not de-polarization of the heart itself that leads to the discomfort of the procedure. The problem, therefore, of dispensing with anesthesia reduces to that of increasing the efficiency with which electrical energy is delivered to the heart, in order that the extracardiac current flow may be decreased to a tolerable level. Viewed this way, the problem of administering countershock to conscious patients is essentially similar to that of pacing the heart in a tolerable fashion without resort to intra-cardiac electrodes. Both problems have interested us and we have approached both in basically the same way, by using an esopha-geal electrode.* Our purpose has been to achieve a greater proximity of the electrodes to the heart. Our technic has been to place one electrode in the esophagus, contiguous with the heart, and the other on the precordium. We hoped that this gain in electrical proximity would sufficiently improve the efficiency of energy delivery so that extracardiac current flow …