Efficacy of Dexamethasone for Prevent Vomiting in Leukemic Children Who Receive Intrathecal Chemotherapy

Inclusion Criteria: * Patients aged between 2-15 years who underlying acute lymphoid or nonlymphoid leukemia and need to receive ketamine and intrathecal chemotherapy. * Personally signed and dated informed consent and assent document indicating that the subject (or legally acceptable representative) has been informed of all pertinent aspects of the trial prior to study entry. Exclusion Criteria: * Patients who had a known allergy to ketamine or dexamethasone. * Patients who had contraindication for ketamine or dexemethasone such as hypertension, increased intracranial pressure or central nervous system mass lesion, major psychiatric , and hyperglycemia. * Patients who concurrent with nausea and vomiting during that time. * Patients who received ondansetron or other antiemetic before doing Procedure. * Patients who received other chemotherapy before or after 24 hours.