The effect of dopamine on hepatic-splanchnic blood flow after open heart surgery

Dopamine (3,4 dihydroxyphenylethylamine) increases cardiac output and in particular the renal blood flow at the expense of other regional vascular beds not yet defined. Since the results of dopamine-induced changes in splanchnic perfusion are inconsistent, the effect of 6 mcg/kg/min dopamine was studied in 9 patients early after open heart surgery. Estimated hepatic blood flow (EHBF) was calculated from the concentration-time slopes of Indocyanine Green (ICG, Cardiogreen) in arterial and hepatic venous blood following single intravenous injection. Blood volume was measured using 51Cr tagged red cells. Cardiac output was determined according to the Fick method. 6 mcg/kg/min dopamine caused a mean EHBF-increase of 82%, from 492 +/- 64 to 824 +/- 80 ml/min/m2 (P less than 0.001). Related to the corresponding increase in cardiac index (CI) from 2.6 +/- 0.2 to 3.8 +/- 0.3 1/min/m2 (P less than 0.001), the EHBF/CI-ratio changed from 18.5 to 21.7% (P less than 0.025). The arterial-hepatic venous oxygen difference was reduced from 7.40 +/- 0.53 to 4.91 +/- 0.60 Vol% (P less than 0.001). It was concluded that splanchnic perfusion does not contribute to the preferential increase of renal blood flow under dopamine under the above mentioned conditions. Dopamine had the most beneficial effect on EHBF in two cases where the latter was severely reduced.