Ha 2015.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Ondansetron (group O) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 31 Received treatment (n): 31 Analysed (n): 31 Age (mean ± SD, median (IQR), median (range)): 54 ± 10 Weight (mean ± SD, median (IQR), median (range)): 61 ± 10 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 22/9/0/0 Gender (female in %): 70.97 Non‐smoker (%): 90.3 History of PONV/motion sickness (%): 3.2/22.6 Type of general anaesthesia: balanced anaesthesia (sevoflurane, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 231 Use of perioperative opioids (if yes, which?): 1084 µg intraoperative remifentanil, 50 µg fentanyl during skin closure, tramadol as rescue analgesic Type of surgery: microvascular decompression with retromastoid craniotomy Ramosetron (group R) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 31 Received treatment (n): 31 Analysed (n): 31 Age (mean ± SD, median (IQR), median (range)): 53 ± 10 Weight (mean ± SD, median (IQR), median (range)): 60 ± 10 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 24/7/0/0 Gender (female in %): 70.97 Non‐smoker (%): 96.8 History of PONV/motion sickness (%): 6.5/19.4 Type of general anaesthesia: balanced anaesthesia (sevoflurane, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 261 Use of perioperative opioids (if yes, which?): 1126 µg intraoperative remifentanil, 50 µg fentanyl during skin closure, tramadol as rescue analgesic Type of surgery: microvascular decompression with retromastoid craniotomy Included criteria: 20 to 75 years of age, ASA I or II, scheduled for microvascular decompression (MVD) with retromastoid craniotomy (RMC) Excluded criteria: pregnancy; having undergone chemotherapy or ventriculoperitoneal shunt insertion; allergy to ondansetron or ramosetron; having undergone antiemetic therapy within 24 hours before the operation; having systemic steroid therapy within 24 hours before the operation or up to 48 hours during the postoperative period; having had an emergency operation; with cardiovascular disease, respiratory disease, renal disease, or hepatic disease; Glasgow Coma Scale Score < 13 points Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, non‐smoker, history of PONV/motion sickness, perioperative opioids): no; (duration of anaesthesia): yes
Interventions	Intervention characteristics Ondansetron (group O) Dose: 8 mg Time point of administration: at onset of dural closure Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV Ramosetron (group R) Dose: 0.3 mg Time point of administration: at onset of dural closure Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV
Outcomes	Vomiting (PACU, 0 to 1 hour) Outcome type: dichotomous outcome Vomiting (6 to 24 hours) Outcome type: dichotomous outcome Sedation/drowsiness (PACU, 1 to 6 hours, 6 to 24 hours, 24 to 48 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: Korea Setting: inpatient, single‐centre Author's name: Kyeong Tae Min Institution: Yonsei University College of Medicine, Anesthesia and Pain Research Institute, Seoul, Korea Email: ktmin501@yuhs.ac Address: Department of Anesthesiology and Pain Medicine, Yonsei University College of Medicine, Anesthesia and Pain Research Institute, 50, Yonsei‐ro, Seodaemun‐gu, Seoul 120‐752, Korea Duration of study: NA Language: English Study's primary outcome: NA Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were randomly allocated to receive ondansetron (group O) or ramosetron (group R) according to a computer grouping program"
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the study medication was prepared by one of the investigators (Ha, SH) in identical 5 ml syringes and administered at an equal volume of 4 ml (ramosetron was prepared with 2 ml of normal saline). The other investigators were unaware of which drug was being administered to the patients"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "investigators who were unaware of the patient treatment group evaluated the occurrence and severity of nausea, the occurrence of vomiting, pain intensity levels, and the requirements of rescue antiemetics or analgesics at the PACU at intervals of 1–6 hours, 6–24 hours and 24–48 hours after surgery"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "sixty‐two patients (31 patients in each group) among the 64 patients enrolled in the study were analyzed because two patients (1 in group O and 1 in group R) violated the experimental protocol"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	High risk	Quote: "demographic data showed no statistical significance" Quote: "but the anesthetic duration in group R was longer than that in group O (231 ± 41 minutes vs. 261 ± 53 minutes, P = 0.01, Table 1). The overall incidence rates of..." Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, non‐smoker, history of PONV/motion sickness, perioperative opioids): no; (duration of anaesthesia): yes