Intraoperative and early postoperative gastric intramucosal pH predicts morbidity and mortality after major abdominal surgery.

The present study was undertaken to investigate the correlation between the intraoperative and postoperative gastric intramucosal pH (pHi) with important perioperative variables and to explore any potential relationship of the measured pHi with the patients' postoperative course. A prospective study was carried out in a group of 48 patients who underwent major abdominal operations over an 8-month period at St. John Hospital and Medical Center. An automated air tonometer was used for gastric pHi monitoring. Twenty-eight elective and 20 emergency abdominal operations were performed in 23 men and 25 women. Twenty-six patients (54%) required postoperative hospitalization in the Intensive Care Unit (ICU). Seventeen patients (35%) developed early postoperative complications. The non-ICU and ICU mortality rates were 4.5 and 19.2 per cent respectively. The mean intraoperative pHi (pHiOR) and postoperative pHi (pHiPO) ranged between 7.03 and 7.58 (7.38+/-0.12) and 6.89 and 7.56 (7.35+/-0.12) respectively (mean +/- standard deviation). There was a significant decrease of the gastric pHi at the first hour intraoperatively compared with the pHi after induction to anesthesia (7.44 vs 7.38+/-0.14, P < 0.001). Patients who underwent emergent abdominal procedures were characterized by lower pHiOR and pHiPO values (7.43+/-0.08 vs 7.30+/-0.13 and 7.39+/-0.84 vs 7.30+/-0.15, P < 0.001 and P < 0.05). Similarly patients who required surgical ICU admission had significantly lower pHiOR and pHiPO measurements (7.3+/-0.12 and 7.28+/-0.12) compared with the rest (7.46+/-0.06 and 7.43+/-0.06; P < 0.001). Overall, lower pHiOR and pHiPO values were associated with the occurrence of postoperative complications (P < 0.001), the postoperative mortality (P < 0.001), the requirement for postoperative mechanical ventilator (P < 0.001) and its duration (P < 0.001), longer ICU stay (P < 0.001), and prolonged hospitalization (P < 0.05). Evidence of intraoperative and early postoperative gastric mucosal ischemia (pHiOR and pHiPO < or = 7.32) was observed in 12 (25%) and 15 (31%) patients respectively. The incidence of postoperative complications and the mortality rate were higher in this group of patients (P < 0.001). At a cutoff point of 7.32 gastric pHiOR gave a sensitivity of 69 per cent and specificity of 97 per cent for predicting postoperative complications as well as a sensitivity and specificity of 67 per cent and 81 per cent for predicting death. Intraoperative and early postoperative gastric pHi is a reliable predictor of patient outcome after major abdominal operations. Splanchnic ischemia may play an important role in determining early complications and survival; therapy guided by the gastric pHi might improve outcome.