Anesthetic strategies to prevent vomiting include using regional anesthesia whenever possible and avoiding medications that cause vomiting. Medications to treat and prevent PONV are limited by both cost and the adverse effects. People with risk factors likely warrant preventive medication, whereas a "wait and see" strategy is appropriate for those without risk factors. Preoperative fasting
Fasting guidelines often restrict the intake of any oral fluid 2-6 hours preoperatively, but in a large retrospective analysis in Torbay Hospital, unrestricted clear oral fluids until transfer to theatre could significantly reduce the incidence of postoperative nausea and vomiting without an increased risk in the adverse outcomes for which such conservative guidance exists. Medications
A multimodal approach to treating a patient with PONV can be efficacious. Numerous patient factors and medication adverse effects must be taken into consideration when selecting a treatment regimen. Serotonin (5-HT3) receptor antagonists can be administered as a single dose at the end of surgery. Adverse effects include prolongation of the QT interval on electrocardiogram (EKG). Medications include ondansetron, granisetron, and dolasetron. Anticholinergics can be used as a long-acting patch placed behind the patients ear. Adverse effects include dry mouth and blurry vision. Care must be taken when handling the patch, as transfer of medication to the eye can induce pupillary dilation. Avoid use in elderly patients. Medications include scopolamine. Glucocorticoids have direct antiemetic effects and can reduce need for postoperative opioids. Adverse effects include a transient increase in serum glucose level, and poor wound healing (controversial). Medications include dexamethasone.
Postoperative nausea and vomiting (PONV) is the phenomenon of nausea, vomiting, or retching experienced by a patient in the postanesthesia care unit (PACU) or within 24 hours following a surgical procedure. PONV affects about 10% of the population undergoing general anaesthesia each year. PONV can be unpleasant and lead to a delay in mobilization and food, fluid, and medication intake following surgery. Cause
Emetogenic drugs commonly used in anaesthesia include nitrous oxide, physostigmine, and opioids. The intravenous anaesthetic propofol is currently the least emetogenic general anaesthetic. These medications are thought to stimulate the chemoreceptor trigger zone. This area is on the floor of the fourth ventricle and is effectively outside of the blood-brain barrier, which makes it incredibly sensitive to toxin and pharmacological stimulation. Several neurotransmitters are known, such as histamine, dopamine, serotonin, acetylcholine, and the more recently discovered neurokinin-1 (substance P). Risk factors
A 2008 study compared 121 Japanese patients who experienced PONV after being given the general anesthetic propofol to 790 people who were free of postoperative nausea after receiving it. Those with a G at both copies of rs1800497 were 1.6 times more likely to experience PONV within six hours of surgery compared to those with the AG or AA genotypes, but they were not significantly more likely to experience PONV more than six hours after surgery.PONV results from patient, surgical, and anesthetic factors.Surgical factors that confer increased risk for PONV include procedures of increased length and gynecological, abdominal, laparoscopic  and ENT procedures, and strabismus procedures in children.