Gastric mucosal pH does not reflect changes in splanchnic blood flow after cardiac surgery.

Despite the widespread use of gastric tonometry to assess splanchnic oxygen transport, no human data are available on the relationship between splanchnic blood flow, splanchnic oxygen delivery and gastric mucosal pH. We have studied the effect of splanchnic blood flow and oxygen delivery on gastric mucosal pHi after cardiac surgery. During the first postoperative hours of intensive care, dopexamine was infused to increase cardiac output in eight patients, while six patients served as controls. Gastric mucosal pH (gastric tonometry), splanchnic blood flow and splanchnic oxygen delivery and consumption (dye dilution) were measured. Dopexamine administration significantly increased splanchnic blood flow (0.72 vs 1.02 litre min-1 m-2) (P < 0.05) and oxygen delivery (117 vs 161 ml min-1 m-2) (P < 0.05) compared with baseline values. However, splanchnic oxygen consumption remained unchanged and gastric mucosal pH levels decreased (7.30 vs 7.25) (P < 0.05). The proportion of splanchnic blood flow of cardiac output did not change in response to infusion of dopexamine, that is dopexamine did not favour blood flow distribution to the splanchnic region. In the control group there were no changes in splanchnic blood flow and oxygen delivery, while splanchnic oxygen consumption increased (36 vs 39 ml min-1 m-2) (P < 0.05) and gastric mucosal pH tended to decrease (7.33 vs 7.29) (ns). We conclude that after cardiac surgery gastric mucosal pH did not reflect changes in splanchnic blood flow and oxygen delivery suggesting heterogeneous or inadequate blood flow distribution within the splanchnic region.