Prevention of Postoperative Nausea and Vomiting in Surgical Patients

Research Plan 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 provide scientifically convincing evidence to support the need for a 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 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 higher incidence of PONV. We hypothesize that a regimen of low dose dronabinol
preoperatively is superior in efficacy to a standard antiemetic in preventing the incidence
of PONV, and thus not only improve patient satisfaction but also reduce length of stay in
patients undergoing surgery that is potentially outpatient based.

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, high risk surgical patients will be randomized to receive
either the study drug oral dronabinol (5 mg) preoperatively and 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 the VA, 2/3 of our patients are scheduled for outpatient surgical procedure
everyday. Our regimen will minimize postoperative and postdischarge nausea and vomiting,
improve 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 and
efficacious could substantially impact on the experience and the outcome of the veteran
undergoing surgery.

Inclusion Criteria:

- The patients undergoing outpatient operations for intra-abdominal or abdominal wall
procedures (e.g. hernias) under general anesthesia.

- Patients that are at increased risk for PONV based on the Koivuranta risk scoring
system, with inclusion of patients having a risk score of 2 or more than 2.

- Ability to give informed consent.

- Veteran eligible for treatment.

Exclusion Criteria:

- Patients <18 years old

- Patients with a history of hypersensitivity to cannabinoids or sesame oil

- Patients with current substance abuse.

Substance abuse will be identified meeting one or both of the following criteria:

- a) Review CPRS to identify inpatient, residential, or outpatient treatment for
alcohol or drug dependence recorded in CPRS within the preceding six months.

OR

- b) Patient report. Exclude patients who report current marijuana or cocaine use
within the past 30 days.

If a drug screen is clinically indicated and is positive the patient will NOT be entered
into the study.

- Patients taking medications known to have significant drug-drug interactions with the
prescribed drug and study drugs, Dronabinol and Ondansetron, will be reviewed in
Micromedex. Micromedex is a medication database used by CAVHS. If the drug could
have a drug-drug interaction with either dronabinol or ondansetron the patients will
NOT be entered into the study. If a drug is confirmed via Micromedex not to have a
drug-drug interaction, the patient will be eligible for study participation.

- Pregnant women

- Patients with prolonged QTC intervals on EKG.

- Patients enrolled in another clinical trial at the time of randomization.

- Inability to adhere to study protocol