Respiratory Function of Dexmedetomidine in Patients Undergoing Pleuroscopy

Inclusion Criteria: * Age ≥ 18 years old * American Society of Anesthesiologists (ASA) physical status of I-IV * scheduled to undergo medical thoracoscopy/pleuroscopy. Exclusion Criteria: * general anesthesia within 7 days prior to study entry * received an α2-agonist or antagonist within 14 days before the procedure * received an intravenous opioid within 1 hour * received an oral or intramuscular opioid within 4 hours from procedure * New York Heart Association class ≥3 * acute unstable angina * acute myocardial infarction (confirmed by laboratory findings) in the past 6 weeks * heart rate (HR) ≤45-50 bpm * systolic blood pressure (SBP) ≤90 mm Hg, * 2nd or/and 3rd-degree Atrioventricular (AV) block (if the patient does not have a pacemaker) * severe functional liver or kidney disease, * obesity (body mass index ≥30 kg/m-2) * severe restrictive interstitial lung disease