Tomar 2017.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Placebo (group B) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 27 Received treatment (n): 27 Analysed (n): 27 Age (mean ± SD, median (IQR), median (range)): 44.6 ± 9.6 Weight (mean ± SD, median (IQR), median (range)): 68.3 ± 9.4 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 51.85 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 88.62 Use of perioperative opioids (if yes, which?): 102.36 µg fentanyl intraoperative, 147.6 µg fentanyl postoperative Type of surgery: unilateral nephrectomy Dexamethasone (group D) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 28 Received treatment (n): 28 Analysed (n): 28 Age (mean ± SD, median (IQR), median (range)): 43.6 ± 10.8 Weight (mean ± SD, median (IQR), median (range)): 70.4 ± 10.48 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 42.86 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 90.8 Use of perioperative opioids (if yes, which?): 98.62 µg fentanyl intraoperative, 98.6 µg fentanyl postoperative Type of surgery: unilateral nephrectomy Included criteria: ASA I or II, either sex, 18 to 65 years of age, undergoing elective unilateral nephrectomy Excluded criteria: history of anaphylaxis to local anaesthetics, diabetes, hypertension, cyanotic heart disease, pregnancy, neurological and respiratory disease, coagulopathy, acid peptic disease Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids): yes
Interventions	Intervention characteristics Placebo (group B) Dose: saline Time point of administration: after induction Route of administration: perineural Rescue antiemetics (if yes, which?): NA Dexamethasone (group D) Dose: 8 mg Time point of administration: after induction Route of administration: perineural Rescue antiemetics (if yes, which?): NA
Outcomes	PONV (0 to 24 hours) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: India Setting: inpatient, single‐centre Author's name: Gaurav Singh Tomar Institution: Department of Anaesthesiology and Critical Care, St. Stephen’s Hospital, Delhi, India Email: spunkygst@gmail.com Address: Flat‐5C, Vidhata Apartment, Vasundhara enclave, Delhi‐96, India 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 using a computer‐generated randomization list into 2 groups (n 5 30)"
Allocation concealment (selection bias)	Unclear risk	Quote: "sealed envelops containing one syringe with bupivacaine and saline or bupivacaine and dexamethasone were prepared by an anesthesiology resident not involved in this study" Judgement comment: not stated; "sequentially numbered, opaque" envelopes (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the enrolled patient, concerned anesthesiologist, and surgeon were unaware of the nature of the drug in each syringe" Quote: "sealed envelops containing one syringe with bupivacaine and saline or bupivacaine and dexamethasone were prepared by an anesthesiology resident not involved in this study"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "all patients were observed postoperatively by anesthesiology resident who was unaware of the study group"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "among 60 patients, 6.67% (2 patients) in group D and 10% (3 patients) in group B were declared as failure to perceive desired effect with medications given. These 5 patients were excluded from the study (Figure 1). Hence, 57 patients were available for data analysis"
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 variables in terms of age, gender, body weight, and height were found to be comparable along with duration of surgery in both groups (P. 0.05) (Table 1). The groups were also comparable regarding fentanyl and propofol consumption during intraoperative period (P. 0.05) (Table 2)" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids): yes