Kim WJ 2013.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Midazolam (group M) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 30 Received treatment (n): NA Analysed (n): 32 Age (mean ± SD, median (IQR), median (range)): 47.0 (39.3 to 47.8) Weight (mean ± SD, median (IQR), median (range)): 60.1 ± 9.0 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 150 Use of perioperative opioids (if yes, which?): 0.5 mg/kg fentanyl IV 15 minutes before end of surgery, IV–PCA device connected, 20 mg/kg fentanyl in 100 mL solution at 0.2 mL/h with a bolus of 1.2 mL and lockout time of 15 minutes Type of surgery: thyroidectomy Ramosetron + midazolam (group RM) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 32 Received treatment (n): NA Analysed (n): 32 Age (mean ± SD, median (IQR), median (range)): 48.5 (37.3 to 54.0) Weight (mean ± SD, median (IQR), median (range)): 59.3 ± 9.2 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): 100 History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 145.0 Use of perioperative opioids (if yes, which?): 0.5 mg/kg fentanyl IV 15 minutes before end of surgery, IV–PCA device connected, 20 mg/kg fentanyl in 100 mL solution at 0.2 mL/h with a bolus of 1.2 mL and lockout time of 15 minutes Type of surgery: thyroidectomy Included criteria: non‐smoking females, 20 to 65 years of age, ASA I or II, anticipated need for opioids for postoperative pain management, 3 or 4 risk factors for PONV Excluded criteria: diabetes mellitus or gastrointestinal disease, smoker, menstruating or had taken an antiemetic medication 72 hours before surgery Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, perioperative opioids): no; (history of PONV/motion sickness): unclear
Interventions	Intervention characteristics Midazolam (group M) Dose: 75 µg/kg Time point of administration: immediately before anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV, dexamethasone 5 mg IV Ramosetron + midazolam (group RM) Dose: ramosetron 0.3 mg, midazolam 75 µg/kg Time point of administration: immediately before anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV, dexamethasone 5 mg IV
Outcomes	Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A1003700) Country: Korea Setting: inpatient, single‐centre Author's name: Hyun Kang Institution: Department of Anaesthesiology and Pain Medicine, College of Medicine, Chung‐Ang University, Seoul, Republic of Korea Email: roman00@cau.ac.kr Address: Department of Anaesthesiology and Pain Medicine, Chung‐Ang University College of Medicine, 224‐1 Heukseok‐dong, Dongjak‐gu, Seoul 156‐755, Republic of Korea Language: English Duration of study: January to September 2012 Trial registry number: ACTRN12612000757819 Study's primary outcome: primary endpoint of this study was severity of PONV
Notes	Two out of 3 groups relevant (midazolam)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "the randomization was based on a random table, generated using the R Project for Statistical Computing (http://www. r‐project.org/) Block randomization with a block size of four and equal allocation was employed to prevent imbalances in treatment assignments. The randomization sequence was generated by a statistician who was not involved with the study"
Allocation concealment (selection bias)	Unclear risk	Quote: "the randomization sequence was generated by a statistician who was not involved with the study. Patient group allocation was revealed to the anaesthetist immediately prior to induction of anaesthesia, by means of numbered and sealed envelopes" Quote: "participate in conducting the study and data collection" Quote: "decisions to enrol or exclude patients were made by an investigator at the preoperative anaesthetic evaluation who did not otherwise..." Judgement comment: not stated; "sequentially numbered, opaque, and sealed envelopes" (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "patient group allocation was revealed to the anaesthetist immediately prior to induction of anaesthesia" Judgement comment: anaesthesiologists were not blinded
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "patients were questioned by an anaesthetic nurse, who was unaware of the group identities, as to the severity of nausea and incidence of retching and vomiting"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "a total of 100 patients were enrolled in the study; four patients were excluded because of incomplete data collection and two patients were excluded because of withdrawal of consent"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: ACTRN12612000757819 (retrospective registration). Date of study start given in the protocol differs from that given in the study report
Other bias	Unclear risk	Quote: "patient characteristics and operative data were similar in the three groups (Table 1)" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, perioperative opioids): no; (history of PONV/motion sickness): unclear