Supplemental perioperative intravenous crystalloids for postoperative nausea and vomiting.

BACKGROUND Postoperative nausea and vomiting (PONV) is a common complication following general anaesthesia. It may be associated with patient dissatisfaction, increased costs of treatment, and unintended admission to hospital.Supplemental intravenous crystalloid administration in the perioperative period may be a simple intervention to prevent PONV. OBJECTIVES To assess whether supplemental intravenous crystalloid administration prevents PONV in patients undergoing surgical procedures under general anaesthesia. SEARCH METHODS We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 7), MEDLINE (1946 to August 2018), Embase (1947 to August 2018), and the Cumulative Index of Nursing and Allied Health Literature (CINAHL; 1971 to August 2018). We searched clinical trials registers for ongoing or unpublished completed studies (August 2018), handsearched three major journals (British Journal of Anaesthesia, European Journal of Anaesthesiology, and Anesthesiology; August 2018), and conducted backward and forward citation searching of relevant articles. SELECTION CRITERIA We included randomized controlled trials of participants older than six months undergoing surgical procedures under general anaesthesia and given supplemental perioperative intravenous crystalloids, defined as a volume larger than that received by a comparator group, to prevent PONV. DATA COLLECTION AND ANALYSIS We used the standard methodological procedures described by Cochrane. MAIN RESULTS We included 41 studies (4224 participants). Participants underwent ambulatory or short length of stay surgical procedures, and were predominantly American Society of Anesthesiology (ASA) class I or II. There is one study awaiting classification and three ongoing studies. All studies took place in surgical centres, and were conducted in geographically diverse settings. Risk of bias was generally unclear across all domains.Supplemental intravenous crystalloid administration probably reduces the cumulative risk of postoperative nausea (PON) (risk ratio (RR) 0.62, 95% confidence interval (CI) 0.51 to 0.75; 18 studies; 1766 participants; moderate-certainty evidence). When the postoperative period was divided into early (first six hours postoperatively) and late (at the time point closest to or including 24 hours postoperatively) time points, the intervention reduced the risk of early PON (RR 0.67, 95% CI 0.58 to 0.78; 20 studies; 2310 participants; moderate-certainty evidence) and late PON (RR 0.47, 95% CI 0.32 to 0.69; 17 studies; 1682 participants; moderate-certainty evidence). Supplemental intravenous crystalloid administration probably reduces the risk of postoperative vomiting (POV) (RR 0.50, 95% CI 0.40 to 0.63; 20 studies; 1970 participants; moderate-certainty evidence). The intervention specifically reduced both early POV (RR 0.56, 95% CI 0.41 to 0.76; 19 studies; 1998 participants; moderate-certainty evidence) and late POV (RR 0.48, 95% CI 0.29 to 0.79; 15 studies; 1403 participants; moderate-certainty evidence). Supplemental intravenous crystalloid administration probably reduces the need for pharmacologic treatment of PONV (RR 0.62, 95% CI 0.51 to 0.76; 23 studies; 2416 participants; moderate-certainty evidence). The effect of supplemental intravenous crystalloid administration on the risk of unplanned postoperative admission to hospital is unclear (RR 1.05, 95% CI 0.77 to 1.43; 3 studies; 235 participants; low-certainty evidence). No studies reported serious adverse events that may occur following supplemental perioperative intravenous crystalloid administration (i.e. admission to high-dependency unit, postoperative cardiac or respiratory complication, or death). AUTHORS' CONCLUSIONS There is moderate-certainty evidence that supplemental perioperative intravenous crystalloid administration reduces PON and POV, in ASA class I to II patients receiving general anaesthesia for ambulatory or short length of stay surgical procedures. The intervention probably also reduces the risk of pharmacologic treatment for PONV. The effect of the intervention on the risk of unintended postoperative admission to hospital is unclear. The risk of serious adverse events resulting from supplemental perioperative intravenous crystalloid administration is unknown as no studies reported this outcome. The one study awaiting classification may alter the conclusions of the review once assessed.