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.
Butyrophenones are typically administered as a single injection at the end of surgery. Adverse effects include prolongation of the QT interval on EKG. Medications include droperidol and haloperidol. Phenothiazines are particularly effective in treating opioid-induced PONV. Adverse effects are dose-dependent and include sedation and extrapyramidal symptoms. Medications include promethazine and prochlorperazine. Neurokinin 1 (NK1) receptor antagonists prevent an emetic signal from being transmitted. Medications include aprepitant and rolapitant. Histamine receptor antagonists can be administered by multiple routes, including orally, intramuscularly, or rectally. Adverse effects include dry mouth, sedation, and urinary retention. Medications include dimenhydrinate and diphenhydramine. Propofol, an anesthetic medication, confers its own antiemetic properties.The 2020 Cochrane Anaesthesia Review Group review of Drugs for preventing postoperative nausea and vomiting in adults
after general anaesthesia: a network meta-analysis (Review)  demonstrated that combination therapy is more effective than single anti-emetic, and that dexamethasone and ondansetron (a commonly used combination) are two of the most effective anti-emetics for PONV. The review adds robust evidence of efficacy for drugs in newer classes, such as aprepitant or fosapreitant, or newer agents in familiar classes, such as ramosetron. The review does not cover the cost effectiveness of the agents included and, despite increased efficacy for newer novel agents, this may preclude their immediate utilisation in anaesthetic practice. Alternative medicine
In conjunction with antiemetic medications, at least one study has found that application to the pericardium meridian 6 acupressure point produced a positive effect in relieving PONV. Another study found no statistically significant difference.