title: Randomized trial on the physiologic impact of NOTES.
abstract: 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.
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. bingenercasey.juliane@mayo.edu.
authors.forename: Juliane
authors.initials: J
authors.lastname: Bingener
authors.affiliation: Department of Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.
authors.forename: Erica A
authors.initials: EA
authors.lastname: Loomis
authors.affiliation: Department of Statistics and Probability, Michigan State University, East Lansing, MI, USA.
authors.forename: Marianne
authors.initials: M
authors.lastname: Huebner
authors.affiliation: Department of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gostout
mesh_terms: D000005:Abdomen / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D004195:Disease Models, Animal; D005260:Female; D006863:Hydrogen-Ion Concentration; D007327:Insufflation / Q000379:methods; D010535:Laparoscopy / Q000379:methods; D057605:Natural Orifice Endoscopic Surgery / Q000379:methods*; D011028:Pneumoperitoneum, Artificial / Q000379:methods*; D011312:Pressure; D013312:Stress, Physiological / Q000502:physiology*; D034421:Sus scrofa; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
chemical_list: D014409:Tumor Necrosis Factor-alpha; D002245:Carbon Dioxide
keywords: Bowel; CO2; Clinical papers/trials/research; Endoscopy; Pneumoperitoneum