Abstract Postoperative pain is related to the gas used for laparoscopy as demonstrated for 100 % nitrous oxide in 2002 by Tsereteli. In a previous trial, we demonstrated that
the use of full conditioning adding 10%nitrous oxide and 4% oxygen to the CO2pneumoperitoneum with humidification and altering the temperature of the insufflation gas, the use of Hyalobarrier gel, and the administration of 5mg dexameth-asone significantly reduced postoperative pain and decreased adhesions. As we believed that just altering the insufflation gas by adding 10 % of nitrous oxide and 4 % of oxygen
would reduce pain and adhesions by itself, we performed a randomized controlled trial on women undergoing robot-assisted laparoscopic myomectomy. Fourteen women un-dergoing robot-assisted laparoscopic myomectomy were randomized 1:1 receiving 86 % CO2+10% N2O+ 4% O2or 100 % CO2. Outcome parameters were postoperative pain (visual analog scale (VAS)) and adhesions observed at second-look laparoscopy after 14 days. Pain and painkiller intake were significantly reduced by using the altered in-sufflation gas (p< 0.05). Adhesions did not show a signif-icant difference, although the study group tended to have less adhesions (p< 0.21). Addition of 10 % N2Oand 4% O2 to the pneumoperitoneum significantly decreased postoperative pain, even in alow number of participants, which suggests a strong effect.