Here is the design of a clinical trial:

Official Title: Efficiency of IV Dexamethasone Compared to Placebo, Administrated After a Lower Limb Blockade is Done, on the Post Operative Pain in Children : a Controled, Randomised, Double Blind Study

Included conditions:
- IV Drug Usage

Study Armgroups:
- {'label': 'dexamethasone', 'type': 'EXPERIMENTAL', 'description': 'IV dexamethasone group : dexamethasone administrated at the induction of general anesthesia, at the dose of 0,2mg/kg (= 0,2mL/kg of a syringe with a 1mg/mL concentration) maximum 8mg (=8mL).', 'interventionNames': ['Drug: Dexamethasone']}
- {'label': 'Placebos', 'type': 'PLACEBO_COMPARATOR', 'description': 'IV placebo group : saline serum is administrated at the induction of general anesthesia, at the dose of 0,2mL/kg, maximum 8mL.', 'interventionNames': ['Drug: Placebos']}

Interventions:
- {'type': 'DRUG', 'name': 'Dexamethasone', 'description': 'IV dexamethasone at the dose of 0,2mg/kg = 0,2mL/kg of a solution of 1mg/mL max 8mg', 'armGroupLabels': ['dexamethasone'], 'otherNames': ['IV dexamethasone']}
- {'type': 'DRUG', 'name': 'Placebos', 'description': 'IV saline serum at the dose of 0,2mL/kg maximum 8mL', 'armGroupLabels': ['Placebos'], 'otherNames': ['IV saline serum']}

Primary Outcomes:
- {'measure': 'Morphinic consumption in the post operative 24H', 'description': 'total morphinic consumption in morphine equivalent in mg', 'timeFrame': 'within 24 hours after dexamethasone or saline serum administration'}

Please estimate the sample size based on the assumption: 
An alpha risk of 5% and a power of 80% are considered. The analysis is based on a two-sample independent t-test. A p value of <0.05 for two-sided tests is considered significant. All analyses are performed according to the intention-to-treat principle.
Sample size estimation
        Based on our practices and published results in adult,28 we estimate that the mean morphine doses administered in the placebo group is 0.7Â±0.6âmg/kg for the 24 first hours and that dexamethasone would reduce these doses by 50% (0.3 mg/kg/day of morphine in the dexamethasone group). Considering an alpha risk of 5% and a power of 80%, and based on the two-sample independent t-test, it is necessary to include 36 patients per group to demonstrate a statistically significant difference.
        As a safety measure and to take into account possible premature stoppages and/or unusable results, we plan to include 40 patients in each group (according to parametric vs non-parametric statistics in the analysis of randomised trials with non-normally distributed data, BMC Medical Research Methodology, 2005).