Postoperative nausea and vomiting (PONV) is a common complication of GA and less often of regional anesthesia. Patients should be stratified preoperatively with regard to their risk of PONV. The incidence of PONV is higher in women, nonsmokers, and patients with a history of PONV or motion sickness and when nitrous oxide and volatile anesthetics are used under GA. Certain types of surgery (cholecystectomy, laparoscopy, and gynecologic) may also increase the risk for PONV.

1. PONV prophylaxis is not recommended in individuals believed to be at low risk. If appropriate, patients with higher risk for PONV should be offered a regional anesthetic technique. If higher-risk patients undergo GA, they should receive antiemetic prophylaxis before or during the surgery. Monotherapy or a combination of two or three antiemetic drugs from different classes is recommended along with measures aimed to diminish the baseline risk factors for PONV: preoperative anxiolysis, use of propofol for induction and maintenance of anesthesia, total IV anesthesia, adequate hydration, and minimization of perioperative opioids. If PONV occurs in a patient who has not received prophylaxis, therapy should be initiated with a serotonin antagonist and supplemented, if necessary, with medications from other classes. In patients who have received prophylaxis, rescue therapy should consist of drugs from classes other than the ones already administered. Administration of drugs from the same class within the first 6 hours after surgery has not been found to be effective in treating PONV. Common antiemetic classes and agents include the following:
2. Serotonin antagonists (ondansetron 4-mg IV bolus) are well studied as prophylactic antiemetics when administered at the end of surgery, and rescue antiemetics when nausea and emesis have occurred postoperatively. However, if a serotonin antagonist has already been given prophylactically, there is no observed benefit of readministration as a rescue agent within 6 hours of the prophylactic dose.
3. Corticosteroids are commonly used for the prevention of PONV. Dexamethasone (4- to 8-mg IV bolus) is the best studied. It is most effective for prophylaxis if administered at induction of anesthesia and can be applied as a rescue drug for established PONV. Methylprednisolone (40-mg IV bolus) can also be used for PONV prevention.
4. Butyrophenones include haloperidol and droperidol. Haloperidol (0.5- to 2-mg IV bolus) is likely as effective as ondansetron (4-mg IV bolus) in preventing PONV. Droperidol (0.625- to 1.25-mg IV bolus) is no longer used as a first-line agent owing to a 2001 US Food and Drug Administration boxed warning associating it with QT segment prolongation and torsade de pointes. A normal QT segment should be documented before droperidol administration and continuous ECG monitoring for a few hours subsequent to the dose. Droperidol is still recommended as an alternative treatment for established PONV.
5. Transdermalscopolamine (1.5 mg) is effective in prophylaxis if applied 2 hours before the start of the surgery. It may cause visual changes and sedation.
6. Phenothiazines include promethazine (6.25- to 12.5-mg IV bolus) and perphenazine (2.5- to 5-mg IV bolus), which have been used for the prevention and treatment of PONV. Promethazine should be injected carefully as extravasation, or subcutaneous injection could result in tissue necrosis.
7. Antihistamines including dimenhydrinate (1-mg/kg IV bolus), and meclizine (50 mg by mouth [PO]) can be used for PONV prophylaxis. The major side effect is sedation.
8. Propofol (20-mg IV bolus) can be used as a rescue agent in the PACU.
9. NK-1 receptor antagonists are a newer class of antiemetic agents. The only one currently available for PONV prophylaxis is aprepitant (40-80 mg PO), and it should be taken within 3 hours prior to induction. Although there are limited clinical data, initial studies are promising.