 This was a randomized, double-blind, parallel, single-dose study. All children admitted to the ICU at Childrens Hospital of Michigan postoperatively who required pain management were candidates. Enrollment required a Childrens Hospital of Eastern Ontario Pain Scale CHEOPS andor Oucher pain score meeting the protocol definition of moderate to severe pain. Each patient was randomly assigned to receive a single dose of either morphine 0.1 mgkg or ketorolac 0.6 mgkg IV as the first postoperative analgesic after arriving in the ICU. Two-milliliter venous blood samples were drawn from a site contralateral to the infusion site. Samples were obtained before the dose and at 15, 30, and 60 minutes, hourly from 1-6 hours, and at 8 and 12 hours timed from the beginning of the infusion. Pain scales were assessed at the time of each pharmacokinetic sample. Plasma was immediately separated and frozen at -80C. Urine was quantitatively collected for 12-24 hours after the study drug was administered. Urine was kept on ice at 3C throughout the collection. At completion of the collection, the urine volume was measured and recorded, and an aliquot was frozen and maintained at -80C. The plasma and urine samples from the morphine treated group in the original study were stored at -80C and were not analyzed. Sets of samples of urine and plasma from 6 subjects over a range of ages have been analyzed to insure that the samples have not deteriorated during storage. This subanalysis study will provide chemical analysis of the plasma and urine samples for morphine, morphine 3 glucuronide M3G and morphine 6 glucuronide M6G; pharmacokinetic analysis of morphine and its metabolites with comparison to demographics; and comparison of the morphine concentrations to the measures of analgesia. The ratio of the area under the plasma concentration vs time curves AUCof M6G with twice the analgesic potency as morphine and M3G with theoretical anti-analgesic properties will be compared to analgesic effects measured by the age-appropriate pain scales. 