Background and Goal of Study: From previous studies, intraoperative high oxygen concentration does not affect postoperative nausea and vomit (PONV). However, we admitted some cases whose PONV were suppressed as oxygen was supplied. We hypothesized that longer postoperative oxygen administration reduces PONV. We investigated whether the duration of post-postoperative oxygen supply affects PONV for patients under laparoscopic gynecological surgery.

Materials and Methods: We randomly assigned 1338 patients undergoing laparoscopic gynecological surgery to 1 hour group (1H) with 1 hour oxygen administration postoperatively or 5 hours group (5H) with 5 hours administration and tested whether the duration difference affects PONV occurrence. Intra-operative anesthetic management was basically total intravenous anesthesia under 40-60% oxygen concentration with intravenous dexamethasone as an antiemetics and intravenous fentanyl-based patient-controlled analgesia for postoperative pain relief. Brief volatile anesthetics was accepted if necessary. For statistical analysis, student t test is used for continuous variables and Fisher's exact test or chi-square test for nominal variables. A p<0.05 was considered statistically significant. Analyses were done with an intention-to-treat(ITT) approach.

Results and Discussion:
687 patients were in 1H group and 651 in 5H group. There were no significant difference in both nausea [43.8% for 1H group and 45.5% for 5H group (p=0.546)], and vomit [21.1% and 24.0% (p=0.214)].  There were also no significant difference in both early(1-5h) and late(5-48h) PONV between two groups.
 
Conclusion(s):Longer postoperative oxygen administration did not suppress PONV incidence. Further investigation will be required.

11 / The relationship between duration of postoperative oxygen administration and postoperative nausea and vomit in patients undergoing laparoscopic gynecological surgery