Heshmati 2004.

Methods	Design: double‐blind, prospective randomized controlled trial Country: Iran Multisite: no International: no Treatment duration: intraoperative period Follow‐up: 24 hours postoperatively Operative procedure(s): tonsillectomy Randomization unit: participants Analysis unit: individual
Participants	90 participants enrolled ASA I children aged 6 to 12 years old with normal BMI scheduled for tonsillectomy under general anaesthesia Exclusion criteria included: a history of motion sickness; PONV; recent common cold. Randomized to: well‐hydrated group (n = 45, 50%); control group (n = 45 50%); no withdrawals were reported. Main characteristics of participants: age (mean, standard deviation): well‐hydrated group 8 years, 3; control group 9 years, 3; number of females/males: 45/45.
Interventions	Well‐hydrated group (intervention): intraoperative infusion of 4 mL/kg/hour Ringer's lactate in addition to standard fluid management Conservative fluid group (control): standard fluid management alone Co‐interventions: none stated
Outcomes	Nausea and vomiting were assessed as dichotomous outcomes. All episodes in the 24 hours following the operation were recorded. They were reported for the overall 24‐hours postoperative time period.
Notes	Trial registration: not stated Funder: not stated A priori sample size estimation: not stated Conducted: dates not stated Declared conflicts of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants were randomly allocated, but no information on the randomization process was provided.
Allocation concealment (selection bias)	Unclear risk	Participants were randomly allocated, but no information on the allocation process was provided.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding of care staff, including the intraoperative anaesthesiologist, was not described.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Nurses responsible for outcome assessment were blinded to allocation group.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals were noted.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	There were no other sources of bias.