The investigators try to find whether thoracic epidural analgesia (TEA) shortens the first gas-out time compared to iv-PCA and promotes earlier discharge after major upper abdominal surgery.

Postoperative ileus (POI) is a prolonged inhibition of coordinated bowel activity after surgery. Half of patients undergoing major abdominal surgery experience POI making it one of the limiting factors for early recovery.

The pathogenesis of POI is multifactorial, and includes neurogenic, inflammatory and pharmacological mechanisms. Thoracic epidural analgesia (TEA) can induce sympathetic block, attenuate inflammatory reaction and limit use of systemic opioids. In addition, sympatholysis induced by TEA can improve microcirculation of bowels and parasympathetic activation can increase gastrointestinal motility.

However, studies comparing TEA and iv-PCA on POI are rare in major upper abdominal surgeries. This study, therefore, compares TEA and iv-PCA in terms of bowel function recovery as a primary endpoint in major upper abdominal surgeries. Secondary endpoints are side effects and hospital stay.

Inclusion Criteria:

• American Society of Anesthesiologists' (ASA) physical statusⅠ-Ⅲ

Exclusion Criteria:

• ASA status of Ⅳ, or more
• Body mass index 30 kg.m2-1 or more
• Severe renal, hepatic, or neurologic diseases
• Opioid or systemic analgesic preoperatively