title: Oncological effects of insufflation with different gases and a gasless procedure in rats.
abstract: BACKGROUND
  The validity of using carbon dioxide (CO2) pneumoperitoneum in laparoscopic tumor surgery has not been investigated thoroughly. The oncologic effects of a gasless procedure and insufflation with different gases were compared in rats.
  
  
  METHODS
  In all the experiments, Donryu rats were randomized to receive a gasless procedure; to receive insufflation with CO2, helium, or air at 10 mmHg for 30 min, or to serve as control subjects without insufflation. In experiment 1, involving 60 rats, ascites hepatoma AH130 cells were inoculated intraperitoneally just before the procedures. The S-phase fraction of the intraperitoneal tumor cells was determined using a flow cytometry on day 7. In experiment 2, 60 rats injected intraperitoneally with latex particles received one of the procedures. At the end of the procedure, peritoneal macrophages were harvested to determine the number of phagocytosed particles. In experiment 3, 75 rats inoculated intraperitoneally with AH130 cells received one of the procedures for 5 consecutive days and were followed for survival analysis.
  
  
  RESULTS
  EXPERIMENT 1: The S-phase fraction was lower after insufflation with air or helium (p < 0.01) than with the anesthesia control condition. Insufflation with CO2 showed a higher S-phase fraction than the gasless procedure or insufflation with air or helium (p < 0.01). EXPERIMENT 2: The phagocytotic activity of peritoneal macrophages was increased by insufflation with helium and air, as compared with the control condition (p < 0.01). Insufflation with CO2 deteriorated the phagocytotic activity more than the gasless procedure (p < 0.05) or insufflation with air or helium (p < 0.001). EXPERIMENT 3: Insufflation with gases demonstrated shorter survival than the anesthesia control condition or the gasless procedure regardless of the gases used (p < 0.01).
  
  
  CONCLUSIONS
  These results suggest that the choice of gases may affect the proliferation of tumor cells and the phagocytotic activity of peritoneal macrophages, insufflation itself may promote tumor spread regardless of the gases used, and the gasless procedure may be oncologically advantageous in this animal model.
authors.affiliation: Department of Surgery, Saitama Medical Center, Saitama Medical School, 1981 Kamoda Kawagoe, Saitama, 350-8550, Japan. 21myoko@saitama-med.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Yokoyama
authors.forename: H
authors.initials: H
authors.lastname: Ishida
authors.forename: T
authors.initials: T
authors.lastname: Okita
authors.forename: N
authors.initials: N
authors.lastname: Murata
authors.forename: D
authors.initials: D
authors.lastname: Hashimoto
mesh_terms: D000388:Air; D000818:Animals; D002245:Carbon Dioxide / Q000008:administration & dosage; D002455:Cell Division; D045744:Cell Line, Tumor; D006371:Helium / Q000008:administration & dosage; D007327:Insufflation / Q000379:methods*; D009369:Neoplasms / Q000473:pathology*; D010587:Phagocytosis; D011028:Pneumoperitoneum, Artificial / Q000379:methods*; D051381:Rats; D016196:S Phase
chemical_list: D002245:Carbon Dioxide; D006371:Helium