 We calculated a sample size of 78 patients in each group for 90 power and 95 confidence. In the calculation, we assumed that the children receiving intravenous mannitol would have a mean coma recovery time of 13.1 SD 18.5 hours and those receiving placebo would have a mean coma recovery time of 22.5 SD 18.5 hours 42.3 effect size, according to a recent study by Aceng, Byarugaba and Tumwine in the same hospital. 