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.
Statistical analysis and sample size calculation
      
        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).
      
      
        Statistical analysis
        The analysis of the results is performed using SAS software V.9.4 (SAS Institute, Cary, North Carolina, USA).
        A descriptive analysis and a comparison of the main sociodemographic and medical characteristics between the two study groups is scheduled, using a Ï2 test for qualitative variables and a Studentâs t-test for quantitative variables. Then, the total amount of nalbuphine or morphineâin morphine equivalentâadministered during the first 24âhours, as well as the three secondary outcomes, are compared between the two groups by using a Mann-Whitney U test or a generalised linear model with adjustment for the patientsâ characteristics if they differ between groups.
        A p value of <0.05 for two-sided tests is considered significant. All analyses are performed according to the intention-to-treat principle. In case of unblinding or for patients quitting the study before the end of follow-up, the measurements will be continued (if possible).