Prevention of Postoperative Nausea and Vomiting (PONV) in Surgical Patients

Anesthesia has become remarkably safe during the past two decades, yet postoperative nausea and vomiting (PONV) continues to be a vexing problem with an unacceptably high incidence. Multiple factors including age, gender, type of surgery and anesthetic agents, perioperative opioid use and duration of anesthesia have been implicated in the cause of PONV. Several new drugs have been introduced during the last two decades to minimize PONV; however the incidence still remains significantly high, ranging from 30% during the first 24 postoperatively to 35% post discharge. Unrelenting PONV results in delayed discharge which is particularly significant after outpatient surgery. The proposed study will examine the anti-emetic properties of orally administered dronabinol given immediately prior to surgery with standard of care intravenous ondansetron given at the end of a surgical procedure in an effort to assess the need for cost effective prophylaxis of PONV.

The chemoreceptor trigger zone (CTZ) functions as emetic chemoreceptor for the vomiting centers. Many antiemetic drugs acting at the level of the CTZ are responsible for vomiting in patients receiving chemotherapy and postoperative patients. Our regimen of oral dronabinol has been proven to reduce the incidence of PONV in patients receiving chemotherapy. We intend to prove that a regimen that has been utilized in patients receiving chemotherapeutic drugs will work in patients with a high risk for developing PONV following surgery. We hypothesize that a regimen of preoperative low dose of dronabinol is superior in efficacy to a standard antiemetic in preventing the incidence of PONV, and thus will not only improve patient satisfaction but will also reduce length of stay in patients undergoing outpatient surgery.

Specific Objectives

1. Reduction of postoperative and postdischarge nausea and vomiting in ambulatory surgery patients.

2. Reduce rate of hospital admissions and length of inpatient stay after outpatient surgery.

3. Improve patient satisfaction after outpatient surgery.

Procedure After informed consent, surgical patients scheduled for outpatient abdominal surgery at the Central Arkansas Veterans Healthcare System (CAVHS) who are at high risk for developing PONV following their procedure will be randomized to receive either the study drug ( preoperative oral dronabinol-5 mg) or standard therapy ( 4 mg ondansetron intravenously at the end of surgery). The outcome measures will be the presence or absence of PONV, the severity and number of such episodes, the event count of rescue antiemetic use and patient satisfaction. All data will be recorded by personnel who are blinded to the drug regimen.

Relevance:

At CAVHS, 2/3 of our patients are scheduled for outpatient surgical procedure everyday. Our regimen will minimize postoperative and postdischarge nausea and vomiting, improve post-operative care unit (PACU) length of stay, minimize unnecessary hospital admissions, provide patient satisfaction and cost containment. The potential for application of this inexpensive intervention to other surgeries is enormous. Reducing the incidence of PONV could have a significant impact on patient satisfaction. The intervention is very low-risk, efficacious, and could substantially impact on the experience and the outcome of the Veteran undergoing surgery.