Cannabidiol Oil Extract for Prevention of Postoperative Nausea and Vomiting

The overall aim of this study is to evaluate the effect of Cannabidiol oil on postoperative nausea and vomiting in elective gynaecological surgical patients undergoing general anaesthesia at the University Hospital of the West Indies, Jamaica and to determine if total analgesic requirements are reduced in the intervention group in the first 24 hours.

Primary Objective:

To compare the incidence of postoperative nausea and vomiting in gynaecological patients who receive 5.5mg of Cannabidiol oil sublingually two to three hours preoperatively to those receiving a placebo in adult elective gynaecological surgical patients.

Secondary Objectives:

• To compare the total amount of rescue anti-emetic medications administered in the first 24 hours postoperatively between the group receiving Cannabidiol oil and the placebo group.
• To compare total analgesic requirements in the first 24 hours postoperatively between those receiving Cannabidiol oil and the placebo group.
• To compare the level of patient satisfaction with the overall anaesthetic experience between the intervention group and the placebo group.

We propose to use a dose of 5.5mg sublingually based on studies which have demonstrated the effectiveness of these for chemotherapy induced vomiting. As there are numerous factors which may affect postoperative nausea and vomiting, including sex, type of surgery and degree of postoperative pain, we will include only female patients undergoing gynaecological surgery to minimise these confounding factors. Of note, this patient group is one of the high-risk groups for postoperative nausea and vomiting, with an incidence in obstetrics and gynaecology of 40-80%. Cannabidiol oil is typically well tolerated with a favourable side effect profile as it non psychoactive. Previous studies have documented that the most common side effects observed were somnolence, sedation and altered mood.

Recruitment of patients will be done on the ward on the day prior to surgery. Time will be allowed for questioning and gathering of information and all risks will be explained. Written consent will be obtained by the researcher, or the research assistant, who will not be involved in the intra-operative management of the patient. The preoperative assessment will be conducted by the anaesthetist as per usual.

The study will be a single centre, double-blinded (patient and attending Anaesthetist) randomised controlled trial. Patients will be randomly allocated into one of two groups:

• Group 1 - Intervention group
• Group 2 - Placebo group

A sample size of 120 patients was calculated, 60 per group, based on an alpha value of 0.05, beta value of 0.2 and an expected proportion of 50%. An increase by 10% was done to address anticipated drop outs. The Intervention group will receive 5.5mg (10 drops) of Cannabidiol oil (infused peppermint oil) sublingually. The placebo group will receive 10 drops of peppermint oil or similar taste.

The intervention (Cannabidiol oil) and placebo will be placed in identical amber, 2ml glass bottles, each having a different assigned number-letter code. The assigned codes will be computer generated and the bottles will be labelled by the pharmacist. The participants will be randomised using an online randomiser programme (www.randomization.com). The pharmacist will assign an appropriate code to the patient/s based on the randomisation table on the day prior to surgery, which will be given to the researcher.

Two to three hours prior to surgery, the assigned agent will be administered by the researcher or assistant. The person administering the intervention will not participate in the conduct of anaesthesia or the collection of data. A protocol is in place to monitor and manage any untoward adverse drug reactions, including anaphylaxis. A standardized technique of General Anaesthesia will be implemented:

• Induction with propofol at 2mg/kg
• Muscle relaxation with Cisatracurium 0.1mg/kg
• Morphine 0.1mg/kg
• Panadol 1g

Data will be collected on medications administered, length of anaesthesia and estimated blood loss. For antiemetic prophylaxis, a standardised protocol of dexamethasone 8mg and dimenhydrinate 0.5mg/kg (~50mg) will be given. In the postoperative period, the rescue protocol in the event of an episode of vomiting or severe nausea is as follows:

1. Step 1: Repeat dose of dexamethasone 4mg
2. Step 2 if no resolution: Kytril 1mg

The proposed study will also include an assessment of the risk of post operative nausea and vomiting, assessment of the presence and severity of any nausea and vomiting and an assessment of patient satisfaction with their overall anaesthesia experience. The Apfel score will be used to assess the risk of postoperative nausea and vomiting, and includes four factors: sex, smoking history, previous history of nausea and vomiting or motion sickness and any plan to use postoperative opioids by the medical team. This produces a score between I and IV and the risk of postoperative nausea and vomiting increases with an increasing score. An Apfel score of I usually carries a 20% risk of postoperative nausea and vomiting and this increases to 80% with a score of IV. The purpose of determining the Apfel score at the time of written consent is to evaluate the effect of the Cannabidiol intervention on not only the overall incidence of postoperative nausea and vomiting, but also to be able to determine how it affects different risk groups. The BARF scale will be used to assess the presence of nausea, which is a subjective sensation and challenging to capture.It consists of six faces, with a scale from 0 to 10. The BARF scale will be checked on arrival to and on discharge from the Post Anaesthetic Care Unit. The Leiden Peri-operative care Patient Satisfaction questionnaire (LPPSq) will be used to assess patient satisfaction and will be conducted 24 to 48 hours postoperatively. It assesses satisfaction with respect to information received, any fears and concerns, professional competence, service and staff-patient relationships.

The data will be collected by the anaesthesia and recovery room nursing staff from the intra-operative anaesthetic and recovery room records. The researcher will then collect all sheets and conduct the patient satisfaction questionnaire between 24 and 48 hours postoperatively. The Apfel score will be assessed by the anaesthetist in charge of the patient at the preoperative visit. The BARF scale will be done by the recovery room and ward nursing staff.

Data will be entered into and analysed using SPSS v. 26.