Drugs for preventing postoperative nausea and vomiting

Patients coming out of anesthesia after surgery may experience nausea or vomiting, and are frequently given drugs to prevent this. But the majority of patients won't benefit from these drugs, according to a large new review of studies.

The review authors examined 737 studies involving 103,237 patients and found that while nine drugs used as antiemetics can prevent nausea and vomiting, their effectiveness and side effects have not been sufficiently studied.

Not all surgical patients are given drugs for nausea and vomiting, said lead author Dr. John Carlisle, consultant anesthetist at Torbay Hospital in Devon, England. "Anesthetists are more apt to give a drug to patients who they think are more likely to experience postoperative nausea and vomiting or to experience further complications should they vomit."

Based on the data from the studies reviewed, Carlisle and his colleague concluded that, if 80 of 100 patients were nauseated after surgery and all 100 patients were given antiemetic drugs, 28 would benefit and 72 would not.

The Cochrane Collaboration is an international organization that evaluates medical research. These reviews draw conclusions about medical practice that are based on evidence collected from many clinical studies, after the reviewers consider both the content and quality of medical studies on a given topic.

The drugs found to reliably prevent nausea and vomiting after surgery, according to the review, are cyclizine, droperidol, granisetron, metoclopramide, ondansetron, tropisetron, dolasetron, dexamethasone and ramosetron.

Up to 80 percent of surgical patients may experience nausea or vomiting after their surgery. Nausea and vomiting are obviously uncomfortable and also can delay hospital discharge. Vomiting can stress surgical wounds, cause electrolyte imbalances and cause bleeding.

Side effects of antiemetic drugs given during or just after surgery to prevent nausea and vomiting are usually mild and include headache, sedation, itchiness, constipation and dizziness.

Carlisle estimates that perhaps 10 million surgical patients in the United States and 2 million in the United Kingdom receive prophylactic treatment for nausea and vomiting each year.

The incidence of nausea and vomiting varies depending on the patient and the type of surgery, said Tong J. Gan, M.D., vice chairman of the anesthesiology department at Duke University Medical Center. While it can occur in up to 80 percent of patients, it is more likely to occur in only about 35 percent.

Women have three times the risk of developing nausea and vomiting after surgery than do men, Gan said, and nonsmokers are also more likely to become nauseated than smokers. The problem is more likely to occur after abdominal hysterectomies, breast surgery, surgery of the middle ear and surgery to correct crossed eyes, he added.

A more important factor in determining which patients are at greater risk is whether they have a previous history of nausea and vomiting after surgery, said Gan, who was not involved with the Cochrane review. Patients should also be asked if they are subject to motion sickness, since this can be a predictive factor, he added.

Carlisle said that screening for patients at increased risk can only go so far. "There will always be some patients who do not have an antiemetic who go on to have nausea or vomiting, and conversely there will always be some patients who have had an antiemetic who would not have had nausea or vomiting even without an antiemetic."

These risk factors can be used to screen patients who are at greatest risk, but are not certain, he said. "By proper screening of patients and proper use of drugs, benefits outweigh the risks."

Proper use of antiemetic drugs can increase their effectiveness and reduce the incidence of side effects such as sedation and dizziness, Gan said. Smaller doses of antiemetics are being used now than were used in years past, with the same efficacy.

The biggest change is that most anesthesiologists use two or three antiemetic drugs in combination, Gan said. "Two drugs reduce risk of nausea far more than one. Three drugs used together reduce risk by 40 to 50 percent."

By Valerie DeBenedette

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