Prospective randomized clinical trial comparing nitrous oxide and carbon dioxide pneumoperitoneum for laparoscopic surgery. Randomized trial of low-pressure carbon dioxide-elicited pneumoperitoneum versus abdominal wall lifting for laparoscopic cholecystectomy. Laparoscopic cholecystectomy using abdominal wall retraction. Hemodynamics and gas exchange, a comparison with conventional pneumoperitoneum. Randomized comparison of conventional carbon dioxide insufflation and abdominal wall lifting for laparoscopic cholecystectomy. Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum is safe even for high-risk patients. Cardiovascular and respiratory changes and convalescence in laparoscopic colonic surgery: comparison between carbon dioxide pneumoperitoneum and gasless laparoscopy. Gasless laparoscopic cholecystectomy: comparison of postoperative recovery with conventional technique. Metabolic and immunologic consequences of laparoscopy with helium or carbon dioxide insufflation: a randomized clinical study. Comparison of N2O and CO2 pneumoperitoneums during laparoscopic cholecystectomy with special reference to postoperative pain.
Recent publications demonstrating the safety and advantages of N2O for pneumoperitoneum (PP) prompted us to reconsider N2O as an agent for PP in general surgical laparoscopy. The purpose of this prospective, double-blind, randomized clinical trial was to determine whether N2O PP has any benefits over CO2 PP.
                One hundred three patients received N2O (group I, n = 52) or CO2 (group II, n = 51) PP for elective laparoscopic surgery. Heart rate, mean arterial blood pressure, end-tidal CO2, minute ventilation, and O2 saturation were recorded before PP, during PP, and in the recovery room. Postoperative pain medication use was recorded. Pain was assessed by means of visual analog scale (VAS) at postoperative hours 2 and 4, and on day 1.
                There were no differences between groups I and II in patient age, gender, weight, anesthesia risk (American Society of Anesthesiologists Score > 2), operative time, duration of PP, or length of hospital stay. Mean end-tidal CO2 increase under anesthesia was greater in group II than group I (3.0 versus 0.5 mmHg, p < 0.001) despite a greater mean intraoperative increase in minute ventilation in group II than group I (0.7 versus -0.2 L/min p < 0.001). The patients who had N2O PP had less pain 2 hours postoperatively (VAS: 4.9 versus 5.7, p <0.05), 4 hours postoperatively (VAS: 3.3 versus 5.1, p < 0.01), and 1 day postoperatively (VAS: 1.7 versus 3.5, p < 0.01) than patients who had CO2 PP. Postoperative narcotic or ketorolac use was not statistically different between groups. There were no adverse events related to either N2O or CO2 pneumoperitoneum.
                These results suggest that the use of N2O PP has sufficient advantages over CO2 that it should be considered as the standard agent for therapeutic PP. Two alternative surgical techniques for elective laparoscopic cholecystectomy (LC), low-pressure insufflation of the peritoneal cavity and abdominal wall lifting (AWL), have been developed over time to minimize the disadvantages associated with CO2-elicited pneumoperitoneum. To the best of our knowledge, the 2 methods have seldom been compared as regards their relative advantages and disadvantages.
                Eighty patients scheduled for elective LC were randomized into either a low-pressure (8 mmHg) CO2 insufflation method (LPLC) group, or a gasless technique using a subcutaneous abdominal wall lifting device (GLC group). The duration of the surgical procedure, the surgical results including level of postoperative pain, and perioperative cardiopulmonary function changes experienced by the members of both groups were compared.
                Laparoscopic surgery was completed for all but 1 patient from each group due to an inadequate surgical-site exposure. There was no mortality for study participants, and no major complications were noted for members of either group. The LPLC group evidenced a shorter surgical duration as compared to the GLC group (77 +/- 28 minutes vs. 98 +/- 27 minutes, respectively; p < 0.01) and a lower incidence of postoperative shoulder pain (2/38 vs. 8/39, respectively; p < 0.05), although significant differences in intraoperative pulmonary function were noted (an increased PaCO2, Pet CO2 and peak-airway pressure and decreased arterial blood pH; p < 0.01) for the LPLC group compared to the GLC group.
                Both alternative methods for this type of surgery appeared feasible and safe for LC. Low-pressure CO2 pneumoperitoneum had a shorter surgical duration and less postoperative shoulder pain compared to the GLC technique, but did not feature any other advantage over the AWL technique with regard to impact on cardiopulmonary function. Disadvantages related to CO2 pneumoperitoneum have led to development of the abdominal wall retractor (AWR), a device designed to facilitate laparoscopic surgery without conventional pneumoperitoneum (15 mmHg CO2). We investigated the effects of the AWR on hemodynamics and gas exchange in humans. We also investigated whether the use of an AWR imposed extra technical difficulties for the surgeon. A pilot study revealed that cholecystectomy without low-pressure pneumoperitoneum was technically impossible.
                A prospective randomized controlled trial: Twenty patients undergoing laparoscopic cholecystectomy were randomly allocated into group 1: AWR with low-pressure pneumoperitoneum (5 mmHg), or group 2: conventional pneumoperitoneum (15 mmHg).
                Surgery using the AWR lasted longer, 72 +/- 16 min (mean +/- SD) vs 50 +/- 18 min compared with standard laparoscopic cholecystectomy. There were no differences between the groups with respect to hemodynamic parameters, although a small reduction of the cardiac output was observed using conventional pneumoperitoneum (from 3.9 +/- 0.7 to 3. 2 +/- 1.1 l/min) and an increase during AWR (from 4.2 +/- 0.9 to 5.2 +/- 1.5 l/min). Peak inspiratory pressures were significantly higher during conventional pneumoperitoneum compared to AWR. A slight decrease in pH accompanied by an increase in CO2 developed during pneumoperitoneum and during the use of the AWR. In both groups arterial PO2 decreased.
                The results indicate that the view was impaired during use of the AWR and therefore its use was difficult and time-consuming. Possible advantages of this devices' effects on hemodynamics and ventilatory parameters could not be confirmed in this study. Gasless laparoscopy using abdominal wall lifting (AWL) has been developed in an attempt to avoid the adverse effects of carbon dioxide pneumoperitoneum that may occur in conventional laparoscopy. However, lifting has been criticized for its poor operative space and surgical invasiveness. This study compared the AWL method with conventional CO2 pneumoperitoneum for laparoscopic cholecystectomy with respect to operation performance, postoperative course, and stress response.
                During a 6-month period, 95 patients with symptomatic gallstones were randomly assigned to receive laparoscopic cholecystectomy with conventional CO2 pneumoperitoneum (CO2 group; N = 47) or the AWL method (AWL group; N = 48). Operative results and operative time were recorded. Cardiopulmonary functions were assessed, and arterial blood gases were analyzed during surgery. Urinary cortisol, vanillylmandelic acid, metanephrines, and nitrogen loss; serum complement 3, C-reactive protein, and interleukin-6; postoperative pain; and the presence of nausea and vomiting were assessed for 48 hours after surgery. Postoperative time to recovery of flatus, tolerance of a full oral diet, and full activity were also determined.
                Only three significant differences were found. First, intraoperative ventilatory function deteriorated significantly less in the AWL group. Second, arterial blood gas determinations and capnography showed a greater decrease in intraoperative arterial pH and compliance with CO2 retention and an increase in peak airway pressure in the CO2 group (P < 0.05), reflecting poorer ventilatory performance. Third, preparation time and total operating time were significantly greater with the AWL method (P < 0.05).
                Although AWL required a longer operation time, our results suggest that the technique may still have value in high-risk patients with cardiorespiratory diseases. Because of absorbed carbon dioxide (CO(2)) and elevated intraabdominal pressure (IAP), CO(2) pneumoperitoneum (CO(2)PP) has potentially harmful intraoperative circulatory and ventilatory effects. Although not clinically significant for healthy patients, these effects are assumed to be deleterious for patients with a high risk for anesthesia (American Society of Anesthesiology [ASA] 3 and 4) and significant cardiopulmonary, renal, or hepatic diseases. The authors assessed CO(2)PP-related adverse effects by comparing ASA 3 and 4 patients who underwent laparoscopic cholecystectomy (LC) with or without CO(2)PP.
                A total of 20 successive ASA 3 and 4 patients who underwent LC were randomized into CO(2)PP (n = 10) and abdominal wall elevator (Laparolift) (n = 10) groups. The parameters for perioperative hemodynamics, ventilation, perfusion of intraabdominal organs, and blood chemistry were recorded periodically from before the induction of the anesthesia until postoperative day 2 and compared between the groups.
                Mean age, height, weight, the proportional number of ASA 3 vs ASA 4 patients, the volume of perioperative fluid loading, and the dose of analgesics did not differ significantly between the groups. The length of the operation was 49.9 +/- 10.6 min for the CO(2)PP group and 50.6 +/- 17.2 min for Laparolift group (nonsignificant difference). The mean central venous pressure (CVP) 30 min after insufflation was higher (12.3 +/- 4.8 vs 7.9 +/- 3.7 mmHg) and the (Gastric Mucosal pH) pHi at the end of the operation was lower (7.29 +/- 0.07 vs 7.35 +/- 0.04) in the CO(2)PP group than in the Laparolift group (p < 0.05). Later, CVP and pHi did not differ significantly. Other parameters of hemodynamics including oxygenation, perfusion, and blood chemistry did not differ significantly.
                For LC for patients with an ASA 3 and 4 risk for anesthesia, no significant adverse effects could be attributed to CO(2 )pneumoperitoneum. For high-risk patients, preoperative preparation and active perioperative monitoring are essential for safe anesthesia for LC with or without CO(2)PP. Gasless laparoscopy produces smaller cardiopulmonary and systemic changes than carbon dioxide (CO2) laparoscopy during colonic surgery.
                Prospective randomized trial.
                Department of Surgery in a university hospital.
                Twenty-two patients scheduled for laparoscopic colonic resection; 5 patients were excluded because of conversion to open surgery (N = 17).
                Patients were randomized to either gasless (n = 9) or conventional CO2 (n = 8) surgery.
                Intraoperative assessment of hemodynamic factors and pulmonary function, and postoperative assessment of pain, pulmonary function, convalescence, and various injury factors were done several times until 30 days after surgery. Surgical complications were noted.
                Descending aorta blood flow after 30 minutes (P=.03) and heart rate after 150 minutes were higher in the CO2 group (P=.009). Central venous pressure, PaCO2 inspiration pressure, and end tidal CO2 level were significantly higher in the CO2 group (P = .05, .03, .04, and .01, respectively). Patients in the CO2 group had less pain during mobilization and coughing (P = .008 and .006, respectively), and were significantly more fatigued (P = .04). No other important differences were observed in intraoperative hemodynamic factors, postoperative convalescence, immunocompetence, or pulmonary function.
                No clinically important differences in cardiovascular and systemic response were observed between patients undergoing CO2 or gasless laparoscopy for colonic disease. We have compared, in a randomized study in 26 patients, immediate and late postoperative recovery after elective laparoscopic cholecystectomy using the gasless, mechanical abdominal wall lift method with conventional carbon dioxide pneumoperitoneum. After the gasless method, tracheal extubation was performed significantly earlier than after the conventional method (P < 0.01). End-tidal carbon dioxide concentrations were significantly higher after pneumoperitoneum for 30 min after operation (P < 0.01). In the conventional group, deviation in Maddox-Wing recordings from preoperative values remained at a significantly higher level during the 3-h recovery room period (P < 0.01). There was a positive correlation between the total amount of carbon dioxide used and duration of drowsiness (r = 0.61, P < 0.001) and the Maddox-Wing deviation (r = 0.62, P < 0.001). Postoperative nausea and vomiting, and right shoulder pain occurred less often after the gasless method (P < 0.05). Late recovery criteria (ability to drink, void and walk) in patients in the gasless group were fulfilled approximately 7 h earlier than in those in the pneumoperitoneum group (P < 0.01). Gasless laparoscopic cholecystectomy resulted in more uneventful and faster immediate and late postoperative recovery than conventional carbon dioxide pneumoperitoneum. Previous studies using animal models have demonstrated that carbon dioxide (CO2) pneumoperitoneum during laparoscopy is associated with adverse physiological, metabolic, immunological and oncological effects, and many of these problems can be avoided by the use of helium insufflation. The present study was performed in patients to compare the effect of helium and CO2 insufflation on intraperitoneal markers of immunological and metabolic function.
                Eighteen patients undergoing elective upper gastrointestinal laparoscopic surgery were randomized to have insufflation achieved by using either helium (n = 8) or CO2 (n = 10) gas. Intraperitoneal pH was monitored continuously during surgery, and peritoneal macrophage function was determined by harvesting peritoneal macrophages at 5 min and 30 min after commencing laparoscopy, and then assessing their ability to produce tumour necrosis factor-alpha (TNF-alpha), and their phagocytic function.
                Carbon dioxide laparoscopy was associated with a lower intraperitoneal pH at the commencement of laparoscopy, although this difference disappeared as surgery progressed. The production of TNF-alpha was better preserved by CO2 laparoscopy, but the insufflation gas used did not affect macrophage phagocytosis. Patients undergoing helium laparoscopy required less postoperative analgesia.
                The choice of insufflation gas can affect intraperitoneal macrophage function in the clinical setting, and possibly acid-base balance. The present study suggested no immunological advantages for the clinical use of helium as an insufflation gas. The outcomes of the present study, however, are different to those obtained from previous laboratory studies and further research is needed to confirm this outcome. To study the possible benefits of N2O pneumoperitoneum, 40 patients scheduled for laparoscopic cholecystectomy for symptomatic cholelithiasis were randomized into either CO2-induced (n = 20) or N2O-induced (n = 20) pneumoperitoneum groups. The intensity of postoperative pain was assessed by the patients themselves using an visual analogue pain score scale. CO2 insufflation caused respiratory acidosis. The total amount of anesthetic enflurane needed was lower in the N2O than in the CO2 group (p < 0.041). The N2O group experienced less pain 1 hour (p < 0.040) and 6 hours (p < 0.017) postoperatively and the next morning. Serum cortisol and plasma adrenaline concentrations in the N2O group did not differ from those in the CO2 group. Patients with N2O pneumoperitoneum seem to have less pain without the side effects caused by CO2. The N2O pneumoperitoneum is a good alternative to the CO2 pneumoperitoneum, especially for prolonged laparoscopic operations in patients with chronic cardiopulmonary diseases.
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.