This study is designed as a randomized, placebo-controlled, double-blinded, clinical trial with two parallel groups. This study investigates the association between a single dose of the drug, Clonidine, and the total amount of opioid administered under and 24 hours after surgery in children undergoing orthopedic limb surgery with the use of tourniquet. The investigators hypothesize that administration of clonidine to children undergoing limb surgery with the use of inflatable tourniquets would reduce post-procedural pain. This study is a pilot to obtain an effect size. Based on this the investigators will calculate a sample size for the main trial enabling us to reach a power of 0.8 with a significans level of 0.05.