Postoperative nausea and vomiting (PONV) is a common complication of anesthesia, affecting 71 million patients per year. Without prophylactic treatment, PONV occurs in 20%-30% of the general population and up to 70%-80% of high-risk surgical patients. Because of its high prevalence, identifying risk factors for PONV and optimizing treatment is essential to the practice of operative anesthesia.
Although many studies have aimed to identify risk factors for PONV, only a few baseline risk factors have been consistently identified: female gender, nonsmoking, and history of PONV or motion sickness. Additional risk factors that are less reliable include migraine, young age, anxiety, and low ASA risk classification.
In addition to these, many patient factors augment risk of PONV but are not actually independent risk factors. Factors that augment risk for PONV include obesity, anxiety, and antagonizing neuromuscular blockade with acetylcholinesterase inhibitors such as neostigmine.
Postoperative nausea and vomiting has also been associated with particular anesthesia techniques, including anesthesia with volatile anesthetics, nitrous oxide, and the use of postoperative opioids. These effects are dose-related, so longer procedures increase risk and so does increased postoperative opioid consumption. In fact, each 30 minute increase in duration of surgery increases PONV risk by 60%.
Type or surgery also correlates with incidence of PONV; however, it is unclear if this is a causal relationship. Abdominal and gynecological surgeries are often implicated, especially laparoscopic procedures where insufflation of the abdomen may play a role in increasing risk. The risk of PONV may also be increased during ear, nose, and throat surgeries where the eye is manipulated causing transient increase in intracranial pressure.
Avoiding Triggers of PONV
Limiting exposure to volatile anesthetics, nitrous oxide, and opioids in any manner will theoretically decrease risk. Patients receiving regional anesthesia are nine times less likely to experience PONV. Use of propofol for induction and maintenance of anesthesia decreases PONV during the first 6 hours of recovery. Avoiding nitrous oxide altogether can decrease incidence of PONV, and is a rather easy strategy in patients with risk factors considering other viable alternatives.
Tailoring a pain management plan to decrease opiate use can also minimize risk. Nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 inhibitors, and gabapentinoids have been shown to have a morphine-sparing effect in the postoperative period and may help limit PONV related to opioid use.
Limiting reversal of neostigmine may possibly decrease risk of PONV, although the effect of neostigmine on PONV is not well established. The patient, surgical and anesthesia factors that increase the risk for PONV are listed in Table 115-1.
TABLE 115-1Risk Factors for PONV