 Eligible pediatric patients that are undergoing tonsillectomy for sleep-disordered breathing or obstructive sleep apnea AND are to be admitted into a monitored setting will be recruited for this study. They will be randomized into two groups:1 Control group receiving continuous infusion of saline placebo and 2 Study group receiving continuous infusion of low-dose ketamine at 0.1 mgkghr. Both patients will receive scheduled oral acetaminophen and rescue intravenous morphine as required. The infusions will be stopped at 0600 the next morning. Morphine requirements, pain scores at selected times, central nervous system side effects, and adverse cardiorespiratory events will be recorded. 