Granisetron vs Granisetron and Dexamethasone on the Reduction of Postoperative Nausea and Vomiting
Granisetron vs Granisetron and Dexamethasone on the Reduction of Postoperative Nausea and Vomiting
Intrathecal morphine (ITM) has proven to be excellent in reducing postoperative pain.
 However, its use has commonly been associated with the occurrence of postoperative nausea and
 vomiting (PONV). In recent years, the combination therapy of antiemetics comprising of a
 serotonin receptor antagonist and corticosteroid has been implemented to diminish the
 occurrence of PONV. Despite being routinely used, the evidence in the efficacy of this
 combination in parturients are conflicting and lacking. In this study, we wish to compare the
 efficacy between the combination therapy of granisetron plus dexamethasone versus granisetron
 alone on the occurrence of postoperative nausea and vomiting (PONV) in 126 parturients
 undergoing elective Caesarean delivery supplemented with intrathecal morphine.
126 parturients aged between 18 and 45 years old who falls within the American Society of
 Anaesthesiology (ASA) physical status I and II undergoing Caesarean deliveries from the 1st
 of October 2020 till the 1st of April 2021 will be enrolled. Informed and written consent
 shall be obtained on recruitment.

 Subjects will be randomised using a computer-generated randomisation software using block
 size 3 into 2 groups; group A and group B each consisting of 63 subjects. The order of
 interventions within each block was random as determined by computer random number generator.
 This technique was chosen to ensure similar numbers of patients in each group at any point
 during the study. Both patients and the assessors of PONV which is the Acute Pain Service
 (APS) team will be blinded.

 Patients are subjected to fasting 6 hours prior to surgery with clear fluid allowed up to 2
 hours before surgery. Intravenous (IV) metaclopromide 10mg, IV ranitidine 50mg and mist
 sodium citrate 30 mls will be administered as part of the acid aspiration prophylaxis.
 Standard monitoring with continuous noninvasive blood pressure monitoring (NIBP),
 electrocardiogram (ECG), respiratory rate and pulse oximetry (SpO2) will be implemented
 throughout anaesthesia.

 Ringer's lactate solution 10ml/kg will be infused for coloading to mitigate hypotension post
 spinal anaesthesia. Spinal anaesthesia will be administered in the upright position,
 implementing a height-based dose for heavy bupivacaine 0.5% administration. Based on the
 subject's height, those who are less than 150cm, 151-154cm and those who are more than 155cm
 will receive 1.5mls, 1.7mls and 1.9mls heavy bupivacaine 0.5% (AstraZeneca) respectively.
 Fentanyl 15-20 mcg and morphine 0.1 mg are added to supplement the spinal anaesthesia.

 On the completion of spinal anaesthesia, 4 mg of dexamethasone will be administered to
 parturients in group A while group B received 1ml of normal saline injected intravenously.
 1mg of IV granisetron will be administered to both groups of subjects after cord clamping.
 These drugs will be given by the anaesthetist administering the spinal anaethesia. The
 anaesthetist in charge is not blinded as this is of paramount importance in ensuring patients
 safety should any complication arises during the delivery of anaesthesia.

 Post surgery, subjects will be monitored in the recovery area for an hour. To supplement ITM
 as the postoperative analgesia, tablet paracetamol 1g qid and voltaren 50mg tds will be
 provided to patients postoperatively. The use of opioid is avoided during the first 24 hours
 of intrathecal morphine administration. Patients will be monitored for complications of ITM
 for 24 hours and assessments will be carried out by the APS team which include an anaesthetic
 medical officer and 2 staff nurses.

 Assessments are made at 1 hour post surgery, 4 hourly for 12 hours post surgery up to 24
 hours after surgery. Episodes of nausea, retching and vomiting will be elicited by direct
 questioning and recorded at each assessors' visit. Nausea is described as an unpleasant
 sensation related to the urge to vomit. Retching is defined as an involuntary effort to vomit
 but without the expulsion of the gastric contents, while vomiting is the when expulsion of
 gastric contents occur.

 The requirement of rescue antiemetics at each time interval will also be documented. Rescue
 antiemetic is given when a patient developed one or more episodes of vomiting. IV ondansetron
 4 mg is given to group A while either IV dexamethasone 4mg or iv ondansetron is given to
 group B. Subsequent requirement of antiemetics will be decided based on the anaesthetist
 discretion.

 Sample size is calculated based the assumption that the combination of a serotonin receptor
 antagonist with a corticosteroid would be superior than its monotherapy and thus, the
 addition of dexamethasone to granisetron would reduce the incidence of PONV from 20% to 3.3%.
 From the calculation using PS software, the sample required for each group is 57, and with
 the additional 10% for dropout rate, this study required 63 patients in each group, giving a
 total of 126 patients.

 Data analysis will be performed using SPSS version 27 for MAC. The incidences of nausea,
 retching, vomiting and the use of rescue antiemetic will be analysed using Chi-Square test.
 Data is presented as percentage and a p-value of <0.05 is considered statistically
 significant.
Inclusion Criteria:

 -  American Society of Anaesthesiologists (ASA) I-II category

 -  2 risks factors or more for PONV according to Apfel Score.

 Exclusion Criteria:

 -  Unfit for spinal anaesthesia.

 -  Coagulopathy

 -  Uncorrected hypovolemia

 -  Indeterminate neurologic disease

 -  Infection at site of injection

 -  Raised intracranial pressure(ICP)

 -  Morbidly obese patients, BMI> 40 kg/m2 according to ICD-10 (International Statistical
 Classification of Diseases 10)

 -  Patients allergic towards morphine.

 -  Contraindicated for antiemetics use

 -  Granisetron: allergy towards Granisetron, prolonged QT interval

 -  Ondansetron: allergy towards ondansetron, prolonged QT interval

 -  Dexamethasone: allergy towards Dexamethasone, uncontrolled Diabetes Mellitus (DM).