Peroperative nitrous oxide delays bowel function after colonic surgery

Forty patients scheduled for elective colonic surgery were allocated at random to receive either nitrous oxide or air during surgery. Preoperative management, surgery, parenteral therapy and postoperative analgesics were similar in both groups. Anaesthetic management included isoflurane, vecuronium by infusion and fentanyl 3 micrograms kg-1 h-1. The air group required a mean inspired isoflurane concentration of 0.8% (SD 0.3), whereas the nitrous oxide group required 0.4% (SD 0.2). No differences were found in duration of operation, blood loss, need for postoperative analgesia or postoperative nausea. Patients in the air group had less gas in the small bowel (P less than 0.005) and in the large bowel (P less than 0.001), and operating conditions were better than in the nitrous oxide group (P less than 0.01). After operation, the air group had significantly earlier bowel function than the nitrous oxide group, with earlier passing of flatus (3.4 (1.2) vs 4.7 (1.4) days) (P less than 0.05) and faeces (4.7 (1.5) vs 6.3 (2.2) days) (P less than 0.05) and required a shorter postoperative hospital stay (10.0 (1.3) vs 11.7 (2.5) days) (P less than 0.05).