High intra-operative
oxygen concentration reportedly reduces
postoperative nausea and vomiting (
PONV), but recent data are conflicting. Therefore, we tested whether the effectiveness of supplemental
oxygen depends on the endpoint (
nausea vs.
vomiting), observation interval (early vs. late) or surgical field (abdominal vs. non-abdominal). We randomly assigned 560 adult patients undergoing various elective procedures with a
PONV risk of at least 40% to intra-operative 80% (supplemental) or 30%
oxygen (control). Potential confounding factors were similar between groups. Incidences of
nausea were similar in the groups during early (12% (supplemental) vs. 10% (control), p = 0.43) and late intervals, 26%vs. 20%, p = 0.09, as were the incidences of
vomiting (early: 2%vs. 3%, p = 0.40; late: 8%vs. 9%, p = 0.75). Supplemental
oxygen was no more effective at reducing
PONV in abdominal (40%vs. 31%, p = 0.37) than in non-abdominal surgery (25%vs. 21%, p = 0.368). Thus, supplemental
oxygen was unable to reduce
PONV independent of the endpoint, observational period or site of surgery.