Tibballs 1992.

Methods	Randomised double‐blind controlled trial
Participants	Study period: not reported Setting: Royal Children's Hospital, Melbourne, Australia Inclusion criteria: hospitalised children aged 6 months or older who required endotracheal intubation for upper airway obstruction caused by croup (defined as coryzal symptoms, fever, barking cough, hoarse voice, retraction, inspiratory stridor, or cyanosis developing over several days) Exclusion criteria: children younger than 6 months old; congenital airway anomalies; previous intubations; spasmodic croup (sudden onset without preceding fever or symptoms of upper respiratory tract infection) Baseline demographics (N = 70, 3 excluded): proportion males: treatment: 63%; control: 66% mean (range) age in months: treatment: 19 (6 to 99); control: 19 (6 to 83) croup score: not measured
Interventions	All children received endotracheal intubation under inhalational anaesthesia with halothane, first with an oral endotracheal tube, in order to secure the airway rapidly and assess the diameter, and second substituted with a nasal tube. Humidification was provided with heat and moisture exchangers, with oxygen added as required. The tube was aspirated routinely every 1 to 2 hours to remove secretions. Treatment (N = 38): 1 mg/kg nasogastric prednisolone within 24 hours of intubation and then every 12 hours until 24 hours after extubation Control (N = 32, 3 excluded): 1 mg/kg of placebo within 24 hours of intubation and then every 12 hours until 24 hours after extubation
Outcomes	Use of epinephrine
Notes	Funding source: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "order determined by a table of random numbers"
Allocation concealment (selection bias)	Low risk	Quote: "Unidentified placebo and prednisolone were supplied by the pharmacy in an order determined by a table of random numbers"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "double blind" "Unidentified placebo and prednisolone were supplied by the pharmacy"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: no description of a third‐party outcome assessor. Carried over judgement from blinding of participants and personnel
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: 4% (N = 3) lost because of exclusion due to bacterial infection or protocol deviations, all in the placebo group
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol identified. All prespecified outcomes from methods appear in results.
Other bias	Low risk	Comment: no other sources of bias identified.
Overall risk of bias All outcomes	Unclear risk	Comment: at least 1 domain judged as unclear risk, and no domains judged as high risk.