ABSTRACT Title: Comparison between trendelenburg and reverse trendelenburg positioning on gastric pH during laparoscopic procedures under general anaesthesia: A prospective observational study. Background: Patient positioning during laproscopic surgery under general anaesthesia may alter the gastric pH in the presence of

pneumoperitoneum. Aims: This study was carried out to determine whether significant change in gastric pH occurs during laproscopic surgeries and whether this change is related to patient positioning. Settings and Designs: Prospective observational study in the Department of Anaesthesiology and Critical Care in a tertiary care teaching hospital. Materials and Methods: 50 adult ASA class I and II female patients between 25 to 40 years undergoing diagnostic laproscopy for infertility under general anaesthesia were selected in group T(trendelenburg) and another 50 adult female patients of the same ASA status and age group scheduled for laproscopic cholecystectomy under general anaesthesia were selected in group RT(reverse trendelenburg) . Five to eight ml of gastric secretions were aspirated, before the change in patient position and the same amount before reversal of neuromuscular block, for analysis of pH. Statistical analysis: Statistical difference of means between the groups was calculated using the unpaired t-test. Statistical difference of means between the pre and post-positioning pH value in the same group was calculated using the paired t-test. Differences were considered significant when the P value was <0.05. Results: The pre-positioning and post-positioning pH values in the T group was 2.528 and 3.272 respectively (P=0.001) and the pre and post-positioning pH values in the RT group was 2.644 and 3.028 respectively (P=0.001). The pre-positioning pH values of gastric fluid in the T group and RT group was statistically insignificant. Similarly, the post-positioning pH values of gastric fluid in the T group and RT group was statistically insignificant. Conclusion: Significant change in gastric pH occurs during laproscopic surgeries, irrespective of the patient position during the intraoperative period. Therefore patient positioning does not effect the extent of pH change. Gastric pH change during laproscopic surgery