Does supplemental oxygen reduce postoperative nausea and vomiting? A meta-analysis of randomized controlled trials.

BACKGROUND Studies on the ability of supplemental oxygen to decrease the incidence of postoperative nausea and vomiting (PONV) are inconsistent, with initial studies suggesting benefit while subsequent trials demonstrate no decrease in PONV. METHODS To clarify whether supplemental oxygen is an effective and reliable method to reduce PONV, we performed a systematic review (MEDLINE, Cochrane Library, hand searching and bibliographies, with no language restriction, through March 2006) of randomized, controlled trials comparing perioperative 80% versus 30%-40% Fio(2) on the incidence of PONV. For this systematic review, PONV was defined as any nausea, retching, and/or vomiting in the first 24 h after surgery. The end-points were early PONV (0-6 h), late PONV (6-24 h), and overall PONV (0-24 h). Data from 10 trials with 1729 patients were included in our meta-analysis: 860 received 80% Fio(2) and 869 received 30%-40% Fio(2). RESULTS In patients who received 80% Fio(2),the relative risk (95% confidence intervals) of experiencing early PONV was 0.91 [0.71-1.16]; late PONV, 0.88 [0.69-1.11]; and overall PONV, 0.91 [0.77-1.06]. Results were similar for early, late, and overall nausea and vomiting. CONCLUSIONS The positive results of two initial studies reducing the risk for PONV in patients given 80% Fio(2) were not confirmed by any of the subsequent trials. Considering all available evidence, 80% Fio(2) should no longer be considered an effective or reliable method to reduce overall PONV.