Gases for establishing pneumoperitoneum during laparoscopic abdominal surgery

Background Laparoscopic surgery is now widely performed to treat various abdominal diseases. Currently, carbon dioxide is the most frequently used gas for insufflation of the abdominal cavity (pneumoperitoneum). Many other gases have been introduced as alternatives to carbon dioxide for establishing pneumoperitoneum. Objectives To assess the safety, benefits, and harms of different gases for establishing pneumoperitoneum in patients undergoing laparoscopic abdominal surgery. Search methods We searched The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and Chinese Biomedical Literature Database (CBM) until September 2012. Selection criteria We only included randomized controlled trials comparing different gases for establishing pneumoperitoneum in patients undergoing laparoscopic abdominal surgery under general anaesthesia. Data collection and analysis Two review authors identified the trials for inclusion, collected the data, and assessed the risk of bias independently. We performed the meta-analyses using Review Manager 5. We calculated the risk ratio (RR) for dichotomous outcomes and the mean difference (MD) or standardized mean difference (SMD) for continuous outcomes with 95% confidence intervals (CI). Main results Carbon dioxide pneumoperitoneum versus nitrous oxide pneumoperitoneum Three trials randomized 196 participants (the majority with low anaesthetic risk) to carbon dioxide pneumoperitoneum (n=96) or nitrous oxide pneumoperitoneum (n=100). All of the trials were of high risk of bias. Two trials (n=143) showed lower pain scores in nitrous oxide pneumoperitoneum at various time points on the first post-operative day. One trial (n=53) showed no difference in the pain scores between the groups. There were no significant differences in cardiopulmonary complications, surgical morbidity, or cardiopulmonary changes between the groups. There were no serious adverse events related to either carbon dioxide or nitrous oxide pneumoperitoneum. Carbon dioxide pneumoperitoneum versus helium pneumoperitoneum Four trials randomized 144 participants (the majority with low anaesthetic risk) to carbon dioxide pneumoperitoneum (n=75) or helium pneumoperitoneum (n=69). All of the trials were of high risk of bias. Fewer cardiopulmonary changes were observed with helium pneumoperitoneum than carbon dioxide pneumoperitoneum. There were no significant differences in cardiopulmonary complications, surgical morbidity, or pain scores. There were three serious adverse events (subcutaneous emphysema) related to helium pneumoperitoneum. Carbon dioxide pneumoperitoneum versus any other gas pneumoperitoneum There were no randomized controlled trials comparing carbon dioxide pneumoperitoneum to any other gas pneumoperitoneum. Authors' conclusions 1. Nitrous oxide pneumoperitoneum during laparoscopic abdominal surgery appears to decrease post-operative pain in patients with low anaesthetic risk. 2. Helium pneumoperitoneum decreases the cardiopulmonary changes associated with laparoscopic abdominal surgery. However, this did not translate into any clinical benefit over carbon dioxide pneumoperitoneum in patients with low anaesthetic risk. 3. The safety of nitrous oxide and helium pneumoperitoneum has yet to be established. More randomized controlled trials on this topic are needed. Future trials should include more patients with high anaesthetic risk. Furthermore, such trials need to use adequate methods to reduce the risk of bias.