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An analysis of the mechanisms of pentobarbital induced myocardial depression by a study of electrolyte distribution Robertson, Anne Cochrane


Continuous infusions of barbiturates in artificially-respired animals result in profound cardiovascular depression with terminal cardiac arrest. In an attempt to elucidate the nature of this cardiac depression at a cellular level, tissue electrolyte analyses were performed on mammalian hearts in failure following infusion of the intact animal with sodium pentobarbital. The patterns of electrolyte distribution encountered were compared to those in animals receiving control saline infusions, and to those in cats subjected to partial myocardial ischemia through ligation of the left coronary-artery. Significant species differences in resistance to the cardiolethal effect of pentobarbital were observed. On the basis of differences in effects on electrolyte distribution and pattern of failure, the conclusion was reached that myocardial ischemia was probably not responsible for pentobarbital failure in the cat and the dog. In cat auricles, pentobarbital exerted a selective action on electrolyte metabolism which may have been related to depression of atrial electrical activity. In addition, evidence was found of a direct action of pentobarbital on cardiac contractility independent of Na and K distribution. Control electrolyte values provided support for the hypothesis that electrolyte distribution is related to cardiac automaticity.

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