Riskfactors for nausea and vomiting after general anaesthesia: fiction andfacts

Numerous factors have been claimed to influence postoperative nausea and vo miting (PONV). A critical review of the literatur reveals, that strong evid ence based on original double-blind, randomized, controlled trials or their meta-analyses is only available for very few risk factors. For most other factors, although mentioned in narrative reviews, there is insufficient evi dence. Sufficient evidence on original data or meta-analyses is present for female gender, a history of PONV or motion sickness, non-smoking-status, y oung age, volatile anaesthetics, nitrous oxide and postoperative opioids. F actors with conflicting results are the menstrual cycle, hypnotics for indu ction, mask ventilation and nasogastric tube, the experience of the anaesth etist, muscle relaxants and their antagonists and laparoscopic procedures. Insufficient evidence is present for the other types of operation, psycholo gical factors including anxiety and pain. No evidence due to lack of data a pplies to postoperative movement, hemodynamic stability, hypercarbia and ac id-base-shifts, For adipositas there is not only a lack of evidence for an effect but evidence for a lack of effect based on several multivariate anal yses. In conclusion, we have developed the following simplified view: PONV is mainly caused by opioids and volatile anaesthetics when applied to susce ptible patients (females, non-smoker, positive history of previous sickness ).