In vitro inhibition of tumour growth in a helium-rich environment: Implications for laparoscopic surgery

Background: The recent results of several experimental studies have suggest ed that tumour implantation after laparoscopic surgery for intra-abdominal malignancy may be partly related to the chemical composition of the insuffl ation gas used during surgery. These studies have demonstrated that the use of helium as a laparoscopic insufflation agent for cancer surgery results in less tumour implantation and growth at port sites. To further investigat e these findings, the present study was performed to compare the growth of cultured tumour cells after exposure to simulated laparoscopic environments , rich in helium, carbon dioxide (CO2), or air. Methods: A rat mammary adenocarcinoma cell suspension was exposed to a simu lated laparoscopic environment for 40 min in one of the following groups: ( i) control (atmospheric air. equivalent to a 'gasless' laparoscopic environ ment): (ii) a CO2-rich environment; and (iii) a helium-rich environment. Ce lls were then cultured for 18 h and optical density readings wore used to a ssess the number of viable tumour cells at the end of this period. The expe riment was performed twice using an identical protocol to ensure consistenc y in the results. In a further study, pH was continuously measured using an antimony probe during a 40 min insufflation period and for 10 min after in sufflation. Results: Cell growth was significantly lower after incubation in the helium -rich environment compared to both the CO2 and control groups (P < 0.001). There was a significant decrease in pH in the CO2 group which was not obser ved during exposure to either air or helium. Conclusions: The inhibition of tumour growth in a helium-rich environment d emonstrated by this study, and the reduced incidence of port-site metastase s seen in other experimental studies. suggests that the clinical use of hel ium as an insufflation gas may have important advantages ol er CO2.