title: A risk score to predict the probability of postoperative vomiting in adults.
abstract: BACKGROUND
  The aim of this study was to identify factors most relevant for postoperative vomiting (PV) and to develop a risk score to predict the probability of PV.
  
  
  METHODS
  Adult inpatients scheduled for elective ear, nose and throat (ENT) surgery under general anaesthesia were offered to participate in a prospective study for PV over 24 h. No prophylactic antiemetics were used. The data of 1137 patients were randomized and split into an evaluation set (n=553) and a validation set (n=584). The evaluation set was subjected to logistic regression analysis to quantify the relative impact of anaesthetic, surgical and individual factors and to develop a risk score. The score was then tested by applying it to the validation set. The area under a receiver operation characteristic (ROC) curve was calculated and the predicted and actual incidences of patients were correlated.
  
  
  RESULTS
  In the evaluation set, patient-related factors (female gender, young age, non-smoking, history of PV or motion sickness) and a high duration of anaesthesia were independent risk factors for PV. The probability of PV could be estimated from the equation: PV=1/(1+exp(-z)) where z=1.28 (gender)-0.029 (age)-0.74 x (smoking)+0.63 x (history of PV or motion sickness)+0.26 x (duration)-0.92. In the validation set this score achieved an area under the ROC-curve of 0.78 and the actual incidence correlated strongly with the predicted risks (R2=0.93, P<0.001).
  
  
  CONCLUSIONS
  The data suggest that the probability of PV following ENT surgery under inhalational anaesthesia with low-dose opioids can be predicted by a score mainly based upon patient-related risk factors.
authors.affiliation: Department of Anaesthesiology, University of Wuerzburg, Germany.
authors.forename: C C
authors.initials: CC
authors.lastname: Apfel
authors.forename: C A
authors.initials: CA
authors.lastname: Greim
authors.forename: I
authors.initials: I
authors.lastname: Haubitz
authors.forename: C
authors.initials: C
authors.lastname: Goepfert
authors.forename: J
authors.initials: J
authors.lastname: Usadel
authors.forename: P
authors.initials: P
authors.lastname: Sefrin
authors.forename: N
authors.initials: N
authors.lastname: Roewer
mesh_terms: D000328:Adult; D000367:Age Factors; D000465:Algorithms; D000768:Anesthesia, General / Q000009:adverse effects; D018681:Anesthetics, General / Q000009:adverse effects; D018685:Anesthetics, Inhalation / Q000009:adverse effects; D019540:Area Under Curve; D017558:Elective Surgical Procedures; D005069:Evaluation Studies as Topic; D005260:Female; D005544:Forecasting; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009041:Motion Sickness / Q000150:complications; D009294:Narcotics / Q000009:adverse effects; D010038:Otorhinolaryngologic Diseases / Q000601:surgery; D011183:Postoperative Complications; D011336:Probability; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking; D013997:Time Factors; D014839:Vomiting / Q000209:etiology*
chemical_list: D018681:Anesthetics, General; D018685:Anesthetics, Inhalation; D009294:Narcotics