Randomized trial on the physiologic impact of NOTES

Background: Our previous work revealed significantly less acidosis in swine undergoing natural orifice translumenal endoscopic surgery (NOTES) using endoscopic air insufflation than swine undergoing standard laparoscopy. We wanted to evaluate the differential effects of CO₂ versus intra-abdominal pressure as source for this finding. In addition, we investigated the endocrine stress response between swine undergoing NOTES peritoneoscopy with CO₂ insufflation and animals undergoing standard diagnostic laparoscopy with CO₂. Materials and methods: Twenty-eight (28) female 50-kg domestic pigs were randomly assigned to one of four groups using a permuted block randomization table: Group 1: NOTES using CO₂ insufflation, Group 2: NOTES using air insufflation, Group 3: laparoscopy max pressure 12 mmHg and Group 4: laparoscopy with max pressure 7 mmHg. Invasive monitoring lines were placed. Pneumoperitoneum was established by the respective method and maintained for 90 min, visualizing liver, spleen and colon. Arterial blood gas was obtained at baseline and four additional time points. Serum TNF-α for POD (postoperative day) 1 and cumulative urine adrenaline for the procedure were determined by ELISA. ANOVA and t test were used for statistical comparison. The study was Institutional Animal Care and Use Committees approved. Results: All experiments were completed as outlined. Blood pH showed a significant difference between groups. Serum TNF-α revealed higher levels for NOTES CO₂ on POD 1 than standard laparoscopy (p = 0.03). Conclusion: NOTES animals with CO₂ insufflation initially experienced similar pH compared to standard laparoscopy but recovered to levels seen in low-pressure laparoscopy and NOTES with air. NOTES with CO₂ appears to elicit a stronger stress response in this study than standard or low-pressure laparoscopy or NOTES with air.