The study will evaluate the post-operative morphine-sparing effect, pain reduction, and side effects of a continuous ketamine infusion after tonsillectomy in pediatric patients.

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 mg/kg/hr. 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.

Inclusion Criteria:

• Patients requiring tonsillectomy for diagnosis of sleep disordered breathing/obstructive sleep apnea that will be admitted for overnight cardiorespiratory monitoring, based on positive polysomnography test, positive nocturnal home oximetry, or strong signs/symptoms of OSAS

Exclusion Criteria:

• Patients with significant developmental delay, abnormal airway anatomy, significant co-morbidities such as cardiac disorders, respiratory disorders, neurological disorders, anad renal disorders.
• Previous reaction to study medications.
• Postoperative bleeding within the first 24 hours
• Refusal to be involved in the study..