Objective: Abdominal complications after cardiac surgery while relatively uncommon are associated with a significant mortality. Perioperative splanchnic ischemia appears to be an important cause of these complications. The aim of this study was to evaluate the effects of normothermic cardiopulmonary bypass on global and regional splanchnic blood flow using TEE and continuous gastric tonometry during CABG surgery.Design: Single-arm prospective observational study.Setting: Cairo University hospital cardiothoracic operative theater.Participants: Twenty patients of both sexes undergoing elective on-pump CABG were included in the study.Methods: Superior mesenteric artery blood flow was measured with duplex ultrasound using TEE probe, while gastric mucosal perfusion was assessed using continuous gastric tonometry (Pg-aCO2 gap) simultaneously during CABG surgery under normothermic CPB (>35°C). Measurements were made six times: T1 (after induction of anesthesia), T2 (after initiation of CPB), T3 (30 min after initiation of CPB), T4 (60 min after initiation of CPB), T5 (5 min after weaning from CPB), T6 (end of surgery). Results: Superior mesenteric artery blood flow showed a highly significant decrease from baseline value (p value < 0.01) after initiation of CPB (T2) till its end (T4) and increased shortly after bypass then decreased again significantly below baseline (p value = 0.04) at the end of surgery (T6). While Pg-aCO2 gap showed a highly significant increase from baseline value (p value < 0.01) 30 minutes after CPB initiation (T3) then 5 minutes after weaning from CPB (T5) and at the end of surgery (T6), however no correlation was found between both variables.Conclusion: Normothermic cardiopulmonary bypass is associated with significant splanchnic ischemia that can not be explained by decreased global splanchnic blood flow. TEE allows intraoperative assessment of blood flow to splanchnic viscera.