Intravenous Dexmedetomidine Versus Thoracic Epidural Anesthesia in Patients Undergoing Thoracic Surgery

• invasive blood pressure,arterial blood gas and bispectral index score monitoring [ Time Frame: immediately before anesthesia (T1), 5 min after endotracheal intubation (T2), immediately after incision (T3), 5 min after OLV initiation (T4), 5 min after double-lung ventilation initiation (T5), and immediately after extubation (T6) ] [ Designated as safety issue: Yes ]
  Routine monitoring was applied pre-operatively including a radial artery catheter contralateral to the operated site for invasive blood pressure monitoring and arterial blood gas sampling. Heart rate and mean arterial blood pressure (MAP) were continuously monitored. Arterial oxygen saturation was monitored by pulse oximetry. Inspired oxygen fraction, end-tidal sevoflurane concentration and end-tidal carbon dioxide were measured. The bispectral index score (BIS) was monitored using a BIS sensor.
  
  

• measuring the plasma concentrations of epinephrine, norepinephrine and cortisol. [ Time Frame: immediately before anesthesia (T1), 5 min after endotracheal intubation (T2), immediately after incision (T3), 5 min after OLV initiation (T4), 5 min after double-lung ventilation initiation (T5), and immediately after extubation (T6) ] [ Designated as safety issue: Yes ]
  In the operating room, after placement of the epidural catheter at T4-6 in patients of Group E, a test dose of 3 mL of 1% lidocaine was administered to exclude intrathecal catheter placement.After pre-oxygenation for 3min, general anesthesia was induced with midazolam 0.04 mg/kg, sufentanil 0.5μg/kg, propofol 2-2.5mg/kg and rocuronium 0.6 mg/kg. A left-side double-lumen tube was inserted and the correct position was assured by auscultation and by fibreoptic bronchoscopy before and after the patient was in the lateral decubitus position. The patient's lung was ventilated with an intermittent positive pressure. Plasma samples were taken upon arrival to the operating room for measurements of epinephrine, norepinephrine, and cortisol in each of the three groups.
  
  

The investigators designed a prospective, randomized, placebo-controlled study to determine whether a single-dose of dexmedetomidine versus thoracic epidural anesthesia (TEA) combined with general anesthesia would provide improved hemodynamic stability and reduce the stress hormone responses in patients undergoing thoracic surgery with one-lung ventilation.