The effect of Nitrous Oxide on post-operative gastric pain in Cataract Surgery under general anesthesia with laryngeal mask airway

Background: Gastric distension is one of the troublesome complications of laryngeal mask airway (LMA) use in anesthesia practice. On the other hand, we know that Nitrous Oxide (N2O) can distend the closed gas spaces including in the stomach. We aimed to determine whether N2O can aggravate LMA induced gastric distension and pain. Method: One hundred and sixty four patients aged between 50-65 years, American Society of Anesthesiologists (ASA) status I, and scheduled for cataract surgery under general anesthesia, were randomly allocated in two groups. After induction of anesthesia, it was maintained with propofol and nitrous-oxide oxygen (60%-40%) in group "A" versus propofol and oxygen 100% in group "B". Quality of mask ventilation before inserting LMA, heart rate and blood pressure were monitored and recorded. Using the Visual Analogue Scale (VAS) pain and also the incidence of nausea and vomiting after the surgery were recorded at 10, 20, 30 and 45 minutes after the operation. Data were analyzed using SPSS software, version 16, and P value less than 0.05 was considered as statistically significant in all instances. Results: In group "A", 60 patients (72.3%) did not report any pain after operation and 23 patients (27.7%) reported epigastric pain. In group B, 70 patients (86.4%) did not have any pain, and 11 (13.6%) had epigastric pain. Statistical analysis of the results showed that the incidence of epigastric pain in the two groups was significantly different and those who received N2O suffered more postoperative epigastric pain. Conclusion: According to the results of this study, when we use LMA and we are afraid of postoperative epigastric pain, we can eliminate N2O from our anesthetic drugs.