Addition of nitrous oxide and oxygen to carbon dioxide pneumoperitoneum during laparoscopic surgery for pain reduction: A double-blinded randomized controlled trial

Objective: To examine if peritoneal conditioning with an altered insufflation gas mixture is associated with reduced postoperative pain intensity compared to the standard insufflation gas (i.e., 100% CO2). Design: A prospective, single-centre, randomized, double-blind, superiority trial was performed. Setting: This study was conducted between 4 April 2019 and 10 February 2022 at the Jessa Hospital, Hasselt, Belgium. Population: Patients scheduled for elective gynaecologic laparoscopic surgery. Methods: Seventy-four patients scheduled for elective gynaecologic laparoscopic surgery were randomised to receive either the standard insufflation gas with 100 CO2 (n = 37; control group) or the altered gas mixture of 86% CO2, 10% N2O and 4% O-2 (n = 37; experimental group). Main Outcome Measures: Postoperative pain was assessed at 4, 8 and 24 hours after surgery and on postoperative day (POD) 7 by an 11-point Numeric Rating Scale, with 0 indicating no pain and 10 indicating worst imaginable pain. Results: No significant differences were found between the control and experimental groups regarding postoperative pain at 4, 8 and 24 h after surgery, as well as on POD7. In addition, the median (25% and 75%) total amount of IV piritramide consumption during the first 24 h after surgery was not significantly different between groups (control group: 18.0 [10.0, 27.0] mg vs. experimental group: 17.0 [10.0, 34.0] mg, p = 0.62). Conclusion: The alternative insufflation gas mixture comprising 86% CO2, 10% N2O and 4% O-2 used for the pneumoperitoneum during gynaecologic laparoscopic surgery does not appear to reduce postoperative pain compared to the standard insufflation gas of 100% CO2.