[Validation of a risk score for prediction of vomiting in the postoperative period]

A risk score to predict postoperative vomiting was presented in a recent issue of this journal. In the present study this score was evaluated at another hospital under different surgical and anaesthetic conditions. Furthermore, we examined whether the score, which was originally designed to predict the occurrence of postoperative vomiting (POV) only, is also useful for prediction of postoperative nausea and vomiting (PONV).

The risk score was applied to 226 patients undergoing inpatient orthopaedic surgery under standardised general anaesthesia (propofol, desflurane in N(2)O/O(2), fentanyl, vecuronium, postoperative opioid analgesia). For 24 hours postoperatively, the patients were followed up for the occurrence of nausea, retching, and vomiting. Perioperatively, risk factors for POV were recorded (gender, age, smoking habits, history of previous PONV or motion sickness, duration of anaesthesia). Using these risk factors the individual risk for suffering POV was calculated for each patient. With these data two ROC-curves (for prediction of POV and PONV respectively) were constructed and the area under the ROC-curve (AUC) as a means of the prediction probabilities of the score was calculated.

The incidence of POV as predicted by the score (22,8%) fits well to the actual incidence of this event (19,5%). The score predicts the occurrence of POV significantly better than can be expected by a random estimation. In spite of different surgical and anaesthetic conditions, the accuracy of the prediction in the present dataset was not significantly different from that reported by the authors of the scores in their validation set. Furthermore, the prediction properties for POV (AUC: 0,73) were not different from the prediction of PONV (AUC: 0,72).

The present risk score provides valid prognostic results even under modified surgical and anaesthetic conditions, and, thus, may obviously be applied to other institutions. Furthermore our results support the hypothesis, that individual risk factors rather than the type of surgery or anaesthetic management have a major impact on the occurrence of POV and PONV.