Up to 30 percent of patients vomit after surgery. As well as being distressing for the patient and those nearby, postoperative nausea and vomiting stresses sutures, drains, and intravenous lines; promotes bleeding and venous hypertension; and increases the risk of pulmonary aspiration. Prolonged vomiting may cause problems with hydration and electrolyte balances. Women are two to three times more likely to develop postoperative nausea and vomiting than men, and the incidence appears to be particularly high (up to 84 percent) after breast surgery. Layeeque and colleagues studied the ability of the combination of dronabinol (Marinol; an anticannabinoid) and prochlorperazine (Compazine; an anticholinergic) to prevent postoperative nausea and vomiting in patients who had breast surgery.

The researchers examined the records of 242 women who underwent breast surgery with general anesthetic at a university hospital before and after a change in protocols for standard perioperative care. The control cohort of 127 women had standard care that did not routinely include antiemetic medications. The 115 women in the intervention cohort received standard administration of prophylactic oral dronabinol (5 mg) before anesthesia plus rectal prochlorperazine (25 mg) after anesthesia. Cardiovascular and neurologic statuses were monitored in all patients, and women in the intervention group were asked about possible medication side effects. Episodes of postoperative nausea and vomiting and use of antiemetic medications were measured for both groups.

Six patients in the intervention group did not receive prophylactic therapy, and 20 patients in the control group received prophylactic antiemetic treatment. Nevertheless, by intention-to-treat analysis, the rate of postoperative nausea was significantly lower in the intervention group (15 percent) than in the control group (59 percent). The rate of postoperative vomiting also was significantly different: 3 percent in the intervention group and 29 percent in the control group. Additional antiemetic treatment was given to 60 percent of control patients but to only 11 percent of the intervention group.

Postoperative nausea was significantly more prevalent in patients with cancer (47 percent) than in women with a benign diagnosis (19 percent). Similarly, rates of postoperative vomiting were significantly higher in patients with cancer (22 percent compared with 5 percent in those without cancer). The diagnosis of cancer had odds ratios of 3.88 for likelihood of nausea after surgery and 7.49 for likelihood of vomiting; but the most significant factor in multivariate analysis was being in the intervention group, which had odds ratios of 7.79 for reduction in nausea and 14.65 for reduction in vomiting. No significant side effects were documented during the study.

The authors conclude that routine prophylaxis using drugs targeting two stimulating mechanisms of the emetic center provided effective, inexpensive, and easily administered antiemetic therapy during common surgeries.