This prospective, double blind, placebo-controlled, parallel group study will be conducted in three study centers in Guangzhou, China. Patients aged older than 65 (ASA I-III) undergoing primary elective abdominal surgery with general anesthesia will be involved in this study. According to previous studies and our pilot trial, the sample size was estimated to be 900 subjects (each center recruiting 300 patients). All eligible patients will be randomly assigned to one of two groups: study group receiving parecoxib and control group receiving normal saline. All patients will be managed with by a standard clinical anesthesia protocol with a sevoflurane-based general anesthesia with continuous intravenous remifentanil, followed by a postoperative PCA with morphine. The emergence delirium will be evaluated by two persons blinding to medication and grouping using Riker sedation-agitation scale immediately since tracheal extubation and at specific time points until patients being discharged from PACU. Pain intensity assessments and pain relief assessments will also be conducted by the patients at given time points in 2 days postoperatively. The morphine-sparing effect, tolerability and safety of parecoxib will be investigated as well.

The inclusion criteria of this study includes:

• Aged older than 65;
• Primary elective abdominal surgery under general anesthesia;
• Ability to understand how to use pain assessment scales and PCA device.

The outcome measures of this study includes:

• Emergence Delirium Assessment;
• Pain intensity and pain relief efficacy endpoints;
• Tolerability and Safety Assessments

Inclusion Criteria:

• Aged older than 65;
• Body weight of at least 50 kg;
• Primary elective abdominal surgery under general anesthesia;
• Preoperative health graded as class ASA I-III, based on medical history and physical examination;
• Ability to understand how to use pain assessment scales and PCA device

Exclusion Criteria:

• Emergency or revised abdominal surgery;
• History of known use of analgesics or any other agent that could interfere with analgesic responses during the up to 24 h before receipt of the study medication which including NSAIDs, tricyclic antidepressants, neuroleptic or antipsychotic agents, or corticosteroids (except routine preoperative medication);
• History of known or suspected drug abuse;
• Known allergy, sensitivity, or contraindication to opioid and non-opioid analgesic drugs;
• History of bleeding disorders, peptic ulceration, or anticoagulant use within the past month;
• History of asthma or bronchospasm;
• History of inflammatory bowel disease, a chronic or acute renal or hepatic disorder, coronary heart disease;
• History of dementia and psychological disorder;
• Contraindication to parecoxib.