title: Volatile anaesthetics may be the main cause of early but not delayed postoperative vomiting: a randomized controlled trial of factorial design.
abstract: BACKGROUND
  Despite intensive research, the main causes of postoperative nausea and vomiting (PONV) remain unclear. We sought to quantify the relative importance of operative, anaesthetic and patient-specific risk factors to the development of PONV.
  
  
  METHODS
  We conducted a randomized controlled trial of 1180 children and adults at high risk for PONV scheduled for elective surgery. Using a five-way factorial design, we randomly assigned subjects by gender who were undergoing specific operative procedures, to receive various combinations of anaesthetics, opioids, and prophylactic antiemetics.
  
  
  RESULTS
  Of the 1180 patients, 355 (30.1% 95% CI (27.5-32.7%)) had at least one episode of postoperative vomiting (PV) within 24 h post-anaesthesia. In the early postoperative period (0-2 h), the leading risk factor for vomiting was the use of volatile anaesthetics, with similar odds ratios (OR (95% CI)) being found for isoflurane (19.8 (7.7-51.2)), enflurane (16.1 (6.2-41.8)) and sevoflurane (14.5 (5.6-37.4)). A dose-response relationship was present for the use of volatile anaesthetics. In contrast, no dose response existed for propofol anaesthesia. In the delayed postoperative period (2-24 h), the main predictors were being a child (5.7 (3.0-10.9)), PONV in the early period (3.4 (2.4-4.7)) and the use of postoperative opioids (2.5 (1.7-3.7)). The influence of the antiemetics was considerably smaller and did not interact with anaesthetic or surgical variables.
  
  
  CONCLUSIONS
  Volatile anaesthetics were the leading cause of early postoperative vomiting. The pro-emetic effect was larger than other risk factors. In patients at high risk for PONV, it would therefore make better sense to avoid inhalational anaesthesia rather than simply to add an antiemetic, which may still be needed to prevent or treat delayed vomiting.
authors.affiliation: Department of Anaesthesiology, Julius-Maximilians-University of Wuerzburg, Germany.
authors.forename: C C
authors.initials: CC
authors.lastname: Apfel
authors.forename: P
authors.initials: P
authors.lastname: Kranke
authors.forename: M H
authors.initials: MH
authors.lastname: Katz
authors.forename: C
authors.initials: C
authors.lastname: Goepfert
authors.forename: T
authors.initials: T
authors.lastname: Papenfuss
authors.forename: S
authors.initials: S
authors.lastname: Rauch
authors.forename: R
authors.initials: R
authors.lastname: Heineck
authors.forename: C A
authors.initials: CA
authors.lastname: Greim
authors.forename: N
authors.initials: N
authors.lastname: Roewer
mesh_terms: D000293:Adolescent; D000328:Adult; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D020250:Postoperative Nausea and Vomiting / Q000139:chemically induced*; D011184:Postoperative Period; D012307:Risk Factors
chemical_list: D018685:Anesthetics, Inhalation