Behdad 2011.

Methods	Design: double‐blind, prospective randomized controlled trial Country: Iran Multisite: no International: no Treatment timing: intraoperative period Follow‐up: 24 hours postoperatively Operative procedure(s): tympanomastoidectomy Randomization unit: participants Analysis unit: individual
Participants	97 participants enrolled ASA I males and females, undergoing tympanomastoidectomy under general anaesthesia Screened participants were excluded: if they had significant underlying disease (e.g. hypertension, cardiovascular disease, heart failure, epilepsy, diabetes, gastrointestinal disease, history of motion sickness, history of PONV, anti‐emetic use 24 hours preoperatively, smoking, drug allergy, or ASA greater than I); in the event of intraoperative hypotension (i.e. systolic blood pressure below 80 mmHg) and intraoperative haemorrhage. Randomized to: group G4 (n = 30, 30.9%); group G10 (n = 33, 34.0%); group G20 (n = 34, 35.1%). Main characteristics of participants: age (mean, standard deviation): G4 26.4, 9.5; G10 28.9, 11.2; G20 30.0, 11; number of females/males: 49/48.
Interventions	G4 (control): infusion of 4 mL/kg Ringer's lactate G10 (intervention): infusion of 10 mL/kg Ringer's lactate G20 (intervention): infusion of 20 mL/kg Ringer's lactate Co‐interventions: none stated
Outcomes	Vomiting measured dichotomously Nausea was measured on an ordinal scale of "mild", "moderate", or "severe" Postoperative pain was evaluated by VAS (0 to 10 score range) Antiemetic administration in PACU was recorded Sore throat, thirst, and vertigo were also measured These outcomes were all measured in the recovery room until discharge from the recovery room.
Notes	Trial registration: not stated Funder: not stated A priori sample size estimation: stated Conducted: summer 2009 Declared conflicts of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Paper states participants were (quote) "randomly allocated" but does not explain further.
Allocation concealment (selection bias)	Unclear risk	Paper states participants were (quote) "randomly allocated" but does not explain further.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	It is stated that the study is (quote) "double‐blind", but it is not clear that the surgical care team was blinded to the intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Study personnel measuring outcomes were not aware of group allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals were stated.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	There were no other sources of bias.