Dexmedetomidine for Sedation of Endobronchial Ultrasound-guided Transbronchial Needle Aspiration

Preventing hypoxemia is one of the major goal of studies for bronchoscopic sedation. Dexmedetomidine is a sedative agents via α2 adrenergic agonist, with little respiratory suppression. In the preset study, we evaluate the safety and feasibility of the Dexmedetomidine in the specific bronchoscopic procedure, endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration.

Patients undergoing flexible bronchoscopy (FB) experience procedure-related symptoms. Current guidelines of FB recommend sedation to all patients undergoing FB, except when there are contraindications. Propofol plus an opioid is the common combination used to improve patient tolerance and satisfaction during FB. However, controversy about combining propofol and opioids persists because of the risk of over-sedation and cardiopulmonary depression, especially for the time-consuming endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA). Similar with other published data, around 40% of hypoxemia event was observed during FB sedation in the investigators' hospital. Dexmedetomidine, is a sedative agents via α2 adrenergic agonist, with little respiratory suppression. It has been applied in patients with mechanical ventilation, undergoing gastroendoscopy and extracorporal shockwave lithotripsy. Little evidences are available for Dexmedetomidine in sedation for EBUS-TBNA.

In this study, the investigators will evaluate the safety and feasibility of Dexmedetomidine for sedation of EBUS-TBNA comparing to Propofol for sedation of EBUS-TBNA. Generally, the FB sedation can divided into three parts: the induction (from starting sedative administration to insertion of bronchoscope); the maintenance ( from insertion of bronchoscope to its removal) and the recovery (from bronchoscope removal to patients gain consciousness). The primary endpoint is the proportion of patients with hypoxemia during maintenance of sedation. the investigators will also observe the other sedative outcomes, e.g. blood pressure, sedative drug dosing and patient tolerance and cooperation. The present study will also observe the association between brain perfusion and sedative outcomes via non-invasive monitor. Based on the unique pharmacokinetic property of Dexmedetomidine and the real-time brain perfusion monitor, Dexmedetomidine-based sedation may provide better safety profile for EBUS-TBNA than propofol and discover novel connection between sedative outcomes and brain perfusion.

Eligibility Criteria:
Inclusion Criteria:

* Patients undergoing elective bronchoscopy and sedation

Exclusion Criteria:

* Age less than 20 years
* American Society of Anaesthesiologists (ASA) physical status classification IV or V
* Mallampati score of 4
* Severe sleep apnoea syndrome (apnoea-hypopnea index more than 40)
* Body mass index more than 42 in males or 35 in females
* Neurologic disorders or other conditions contributing to difficulty in assessing response
* Forced expiratory vital capacity (FVC) less than 15 ml/kg body weight, forced expiratory volume in one second (FEV1) less than 1000 ml, or FEV1/FVC less than 35%
* History of second or third degree atrioventricular block, heat rate less than 50 beat per minute or systolic blood pressure less than 90 mmHg
* Pregnancy
* Patients with a known history of allergy to the study drugs, or to eggs, soybeans or sulfite products