Abstract: To investigate the effect of thoracic epidural anesthesia (TEA) on the intramucosal pH (pHi). Methods: Thirty ASAⅠ～Ⅱ patients who were going to undergo colectomy randomly were divided into TEA and control groups. 0.5% bupivacanine of 8?ml or isotonic sodium chloride solution was injected into the epidural space. Gastric mucosal tonometry was placed into the stomach to measure the intramucosal CO2 (PiCO2) and the pHi was calculated before and 60, 120, 180, 240?minutes after epidural injucation. Meanwhile, the concentration of corticoserone and blood glucose were titrated. Results: pHi and PiCO2 had a statistical significance between the groups of 180 and 240 minutes, and the maximal pHi significantly decreased (P<0.01) in the control group (0.16±0.04) compared with that in the TEA group (0.07±0.05). There were 10 patients in the control group and 2 in the TEA group whose pHi<7.32 at the end of the study (P<0.01). There were significant differences between groups in the concentration of corticoserone and blood glucose (P<0.05～0.01). A negative correlation was established between the pHi and the concentration of corticoserone（r=-0.58, P<0.01）. Conclusion: TEA can prevent the decrease of pHi induced by surgical stress and increase the flow of visceral perfusion.

Key words: Anesthesia, epidural, Gastric mucosa, Gastric acidity determination, Abdominal surgery