Effect of ouabain on total vascular capacity in the dog

Whereas the cardiac effects of digitalis glycosides have been extensively studied, less is known of the extracardiac effects of the drug, in particular the effects on vascular capacity. We investigated the effects of parenteral ouabain on vascular capacity in the dog with particular emphasis on transhepatic resistance and its interaction with splanchnic and total intravascular capacity. We studied 49 dogs on total cardiopulmonary bypass in which the splanchnic and extrasplanchnic circulations could be separately perfused and drained, and the portal vein could be vented to systemic venous pressure. The results indicate: (a) ouabain produces a net central displacement of blood at 30 min after administration of 150 ± 70 ml (SEM), (b) this displacement occurs despite a substantial increase in transhepatic resistance, although the early rise in transhepatic resistance may delay the net displacement of blood, and (c) the decrease of overall vascular capacity is due to an effect of ouabain on the capacitance vessels of both the splanchnic and extrasplanchnic circulations. The peripheral vascular capacity effects of ouabain may therefore contribute to overall cardiac performance.