Assessment of splanchnic perfusion during cardiopulmonary bypass by continuous gastric tonometry and transesophageal echocardiography

ABSTRACT

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 [CPB] on splanchnic blood flow using Transesophageal echocardiography [TEE] Doppler-measured superior mesenteric artery blood flow and continuous gastric tonometry during coronary artery bypass graft surgery [CABG]. Twenty patients undergoing elective on-pump CABG were included in that Single-arm prospective observational study. Superior mesenteric artery blood flow [SMA-BF] was measured with duplex ultrasound using TEE probe, while gastric mucosal perfusion was assessed using continuous gastric tonometry during CABG surgery under normothermic [>35°C] CPB. Measurements were made six times Tl [after induction of anesthesia], T2 [after initiation of CPB], T3 [30 min on bypass], T4 [60 min on bypass], T5 [5 min after weaning from CPB], T6 [end of surgery]. Also blood samples were collected for arterial blood lactate levels. SMA-BF 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 at the end of surgery [T6]. While gastric mucosal CO[2]gap [Pg-aCO[2] 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. This study showed that normothermic CPB is associated with a significant reduction of both SMA-BF and gastric mucosal blood flow, however the splanchnic blood flow reduction alone cannot account for mucosal ischemia which may even become worse when blood flow is restored. Transesophageal echo-Doppler allows the intraoperative measurement of blood flow distribution to splanchnic viscera and may be considered a reliable tool specially when coupled with arterial lactate measurement and gastric tonometry to expect which patients well develop splanchnic ischemia during CPB