On average the incidence of nausea or vomiting after general anesthesia ranges between 25 and 30% [Cohen 1994]. Nausea and vomiting can be extremely distressing for patients and is therefore one of their major concerns [Macario 1999]. Vomiting has been associated with major complications such as pulmonary aspiration of gastric content and might endanger surgical outcomes after certain procedures, for example after maxillofacial surgery with wired jaws. Nausea and vomiting can delay discharge and about 1% of patients scheduled for day surgery require unanticipated overnight admission because of uncontrolled postoperative nausea and vomiting.

A 2008 study compared 121 Japanese patients who experienced PONV after being given the general anesthetic propofol to 790 people who were free of post-operative 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.

Postoperative nausea and vomiting results from patient factors, surgical factors, and anesthetic factors. It has been proven that there is a direct like between length of surgery and risk of postoperative nausea and vomiting (PONV). Due to the length of the procedure, abdominal and laparoscopic are at a higher risk for PONV. Procedures in ENT have an increased risk as well due to the involvement of the vestibulocochlear system. In addition to the length of the surgery the dose of the anesthetic also play a large role in the risk of PONV.

Patients that are female or who have a history of postoperative nausea and vomiting are at greater risk. Smokers have a decreased risk, but this would never be recommended by any physician. Older patients suffer less PONV.

Obesity, age less than 16 years, past history of motion sickness and high levels of pre-operative anxiety are also risk factors for PONV.