Effect of digitalis on estimated splanchnic blood flow

Digitalis causes vasoconstriction of peripheral vasculature and has been shown to markedly decrease splanchnic blood flow in experimental animals in doses that are comparable to therapeutic doses in man. The effect of digitalis on splanchnic blood flow in heart failure in experimental animals and in man has been controversial. We found that i.v. ouabin reduced ESBF by 30% to 40% (p less than 0.001) in normal volunteer human subjects, that i.v. digoxin reduced ESBF by 15% to 25% (p less than 0.01) in normal subjects, and that oral digoxin had no discernible effect on ESBF in normal subjects. The difference between the effects of i.v. and oral administration appeared to be due to differences in peak blood levels, which were almost 10 times higher after i.v. administration. Glucagon prevented the effect of i.v. digoxin on ESBF in normal subjects. For patients in heart failure, the effect of i.v. digoxin on ESBF was variable: some patients had decreased ESBF but two had increased ESBF that seemed to be associated with a greater increase in cardiac output.