Splanchnic oxygen transport after cardiac surgery: Evidence for inadequate tissue perfusion after stabilization of hemodynamics

Abstract

Objective. To evaluate the adequacy of visceral oxygen transport and gastric pH(i) after open heart surgery in patients with stable hemodynamics. Design. Nonrandomized control trial. Setting. A general intensive care unit in a tertiary care center. Patients: Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics. Interventions. The effect of dobutamine infusion (6 μg kg-1 min-1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pH(i) by gastric tonometer. Measurements and results. Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2 ± 0.6 vs 4.4 ± 0.71·min-1·m-2: P < 0.05), splanchnic blood flow (0.68 ± 0.28 vs 0.91 ± 0.28 l·min-1·m-2; p < 0.05) and femoral blood flow (0.25 ± 0.08 vs 0.32 ± 0.11 l·min-1·m-2; p < 0.05). Changes in splanchnic oxygen:delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pH(i) did not change (7.30 ± 0.08 vs 7.31 ± 0.06; NS), while in the control group, gastric pH(i) tended to decrease (7.32 ± 0.04 vs 7.28 ± 0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141 + 11 vs 149 ± 11 ml·min-1·m-2; P < 0.05) but did not change in the control group. Conclusions. We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.