The studies addressed different techniques of monitoring hepatic and splanchnic blood flow (SBF) during open heart surgery. Calculations of gastric mucosal pH (pHi) using tonometry was performed in 72 patients, and the effect of dopaminergic stimulation on pH1 was studied in 33 patients. Transesophageal echocardiography (TEE) for determination of hepatic venous flow (HVF) was used in 18 patients and the method was validated against indicator dilution technique with indocyanine green (ICG) in 10 patients. In 9 patients estimations of SBF by low-dose ethanol was validated against ICG. Specific aims: (1) To measure SBF in cardiac surgery with ICG. (2) To study the effect of cardiopulmonary bypass on pH1 and to evaluate the possible effect of dopexamine on a postoperatively low pHi. (3) To evaluate the possible effects on pHi of low-dose dopexamine and dopamine when used for 24 hours as a prophylactic infusion and started directly after induction of anesthesia for cardiac surgery. (4) To estimate HVF with echo-Doppler during open heart surgery and to assess right heart dynamics by recordings of hepatic venous flow patterns. (5) To compare measurements of SBF with ethanol and ICG as indicators. (6) To validate echo-Doppler measurements of HVF against dye extraction estimations of total SBF by continuous ICG infusion, before and during CPB and by low-dose ethanol infusion before, during and after CPB. Results: (I) SBF measured with ICG was 765 (s.e.m. 88) ml/min following induction of anesthesia and did not change during surgery and CPB. (2) An increase in pHi was noted during CPB (p<0.05) followed by a decrease compared to baseline after CPB. Dopexamine reduced pHi compared to the placebo group (p <0.05). (3) pHi and arterial pH did not differ between patients receiving dopexamine or dopamine versus control patients. Both the carbondioxide tension of arterial blood (PaCO2) and of the saline in the tonometer (PtonCO2) changed in parallel with a decrease during CPB and an increase after CPB. (4) HVF measured by ...