OBJECTIVE The effects of increasing cardiac output by epinephrine on indocyanine green plasma disappearance rate (ICG-PDR) and gastric mucosal PCO(2) (P(R)CO(2)) were studied as indicators of splanchnic microcirculation. METHODS A prospective clinical study. METHODS Intensive care unit of a university hospital. METHODS With ethics approval and written consent, 12 elective cardiac surgical patients (5 female, 7 male, 71 +/- 8 years) were studied. METHODS Patients underwent pulmonary artery and left atrial catheterization for clinical indications. Measurements were made at intensive care unit admission and 1 hour after (increased) epinephrine treatment. Mean epinephrine dose was changed from 0.02 to 0.08 microg/kg/min. RESULTS Heart rate significantly increased from 97 +/- 11 to 106 +/- 12 beat/min. Central venous (10 +/- 3 v 10 +/- 4 mmHg) and left atrial (10 +/- 5 v 11 +/- 5 mmHg) pressures were unchanged. Cardiac index and stroke volume index significantly increased from 2.7 +/- 0.5 to 3.2 +/- 0.5 L/min/m(2) and from 28 +/- 6 to 31 +/- 5 mL/m(2), respectively. Although systemic O(2) delivery and O(2) consumption significantly increased, ICG-PDR did not change significantly (ie, from 18.0% +/- 5.6% to 19.5% +/- 6.4% per minute). P(R)CO(2) and PCO(2) gap (difference between regional and end-tidal PCO(2)) significantly increased from 5.4 +/- 1.0 to 5.9 +/- 1.1 kPa and 1.2 +/- 0.8 to 1.5 +/- 0.7 kPa, respectively. CONCLUSIONS Increasing cardiac output by epinephrine in patients after cardiac surgery was not associated with a change in flow-dependent liver function but a deterioration in gastric mucosal perfusion.