Li 2015‐2.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis and combination prophylaxis
Participants	Baseline characteristics Ondansetron (CS group) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 70 Received treatment (n): NA Analysed (n): 70 Age (mean ± SD, median (IQR), median (range)): 48.74 ± 8.21 Weight (mean ± SD, median (IQR), median (range)): 63.26 ± 8.61 BMI (mean ± SD, median (IQR), median (range)): 24.50 ± 2.95 ASA I/II/III/IV (n): NA Gender (female in %): 100 Non‐smoker (%): 100 History of PONV/motion sickness (%): 7.1 Type of general anaesthesia: inhalational anaesthesia (sevoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 126.93 Use of perioperative opioids (if yes, which?): 15.58 µg sufentanil intraoperative, 110.00 mg tramadol postoperative Type of surgery: modified radical mastectomy Dexamethasone + ondansetron (DS group) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 70 Received treatment (n): NA Analysed (n): 70 Age (mean ± SD, median (IQR), median (range)): 48.87 ± 7.48 Weight (mean ± SD, median (IQR), median (range)): 62.17 ± 8.18 BMI (mean ± SD, median (IQR), median (range)): 24.27 ± 3.11 ASA I/II/III/IV (n): NA Gender (female in %): 100 Non‐smoker (%): 100 History of PONV/motion sickness (%): 7.1 Type of general anaesthesia: inhalational anaesthesia (sevoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 112.60 Use of perioperative opioids (if yes, which?): 14.68 µg sufentanil intraoperative, 131.25 mg tramadol postoperative Type of surgery: modified radical mastectomy Included criteria: female, breast cancer, undergoing modified radical mastectomy with neoadjuvant chemotherapy, 18 to 60 years of age Excluded criteria: neurological disease, severe cardiac disease, severe respiratory impairment, chronic disease of the digestive tract, long‐term preoperative use of analgesics, use of antiemetics, smoker Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness, perioperative opioids): no
Interventions	Intervention characteristics Ondansetron (CS group) Dose: 8 mg (sevoflurane) Time point of administration: placebo before anaesthetic induction, ondansetron 30 minutes before end of surgical procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA Dexamethasone + ondansetron (DS group) Dose: dexamethasone 10 mg, ondansetron 8 mg (sevoflurane) Time point of administration: dexamethasone before anaesthetic induction, ondansetron 30 minutes before end of surgical procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA
Outcomes	PONV (0 to 24 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: China Setting: inpatient, single‐centre Author's name: Zhi‐yi Fan Institution: Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Anesthesiology, Peking University Cancer Hospital Institute, Beijing, China Email: 13911114196@163.com Address: Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Anesthesiology, Peking University Cancer Hospital Institute, Beijing 100142, China Duration of study: NA Language: Chinese (Google Translator) Study's primary outcome: NA Trial registry number: NA
Notes	Four groups divided into 2 sub‐studies (2 different anaesthesia regimens: TIVA, inhalational anaesthesia): Li 2015‐1 and Li 2015‐2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: quote: "randomized". No further information on sequence generation provided
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Judgement comment: no statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: no statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: no missing outcome data
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Low risk	Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness, perioperative opioids): no