Postoperative nausea and vomiting (PONV) is common following beast surgery. Dexmedetomidine was reported to a reduced PONV due to opioid-sparing effect. It is not clear if dexmedetomidine itself is useful on reducing PONV. The hypothesis of present study: intraoperative application of single dose dexmedetomidine (0.5 mcg/kg) is is effective than placebo for reducing of PONV and improve postoperative quality of recovery score within 48 postoperative hours.

This study was approved by the Institutional Review Board of Severance Hospital, Yonsei University Health System. After written informed consent was obtained from all patients, aged 20-75 years with ASA physical status class I-II who were scheduled breast cancer surgery under general anaesthesia were enrolled in this study All the patients were randomly assigned to receive dexmedetomidine or placebo during surgery. The primary outcome was quality of recovery determined by QOR-40 in the first 24h after surgery.The secondary outcome measure was PONV assessed by visual analogue scale every 6 hours within 48 postoperative hours.

Inclusion Criteria:

• ASA I, II
• aged 20-70 years
• Undergoing breast cancer surgery

Exclusion Criteria:

• CAOD
• Bradycardia
• QT prolongation