Abdominal surgery causes severe postoperative pain. Multi-modal pain therapy is usually
applied but there is no perfect choice. It depends on physician's skill and situation. The
best regimen is patient-controlled analgesia, but it requires an expensive equipment.
Transdermal fentanyl patch, usually used in chronic pain relief, can steadily release
fentanyl into blood stream for 72 hours, but it has slow onset of 12 hours.
Hypothesis: If Transdermal fentanyl patch is applied 10-12 hours before surgery, it may
provide good analgesia for 72 hours.