Introduction
Gastrointestinal endoscopy plays a very important role in the diagnosis and treatment of gastrointestinal diseases. To facilitate the work of the gastroenterologist and provide patient comfort, patients are given sedation during the endoscopic procedures [1,2]. Propofol is a popular drug during gastrointestinal endoscopy because of its rapid onset, short duration of action, and minimal adverse effects [3-7]. However, propofol may result in sedation-related adverse events such as, respiratory depression and hypotension [8]. Adjuvants are usually needed in endoscopic procedures in order to decrease the propofol dosage and adverse events [9,10]. Dexmedetomidine, a α2receptor agonist, could be an ideal adjuvant to propofol for endoscopy because it provides both analgesia and sedation without respiratory depression [11]. However, the bradycardia caused by dexmedetomidine was often reported [12-16]. Nonaka T et al. [16] demonstrated that that the incidence of bradycardia (defined as a pulse rate ≤ 45 bpm) in the combination of dexmedetomidine with propofol group was higher than that in the propofol alone group (37.9% vs. 10.3%). Whether dexmedetomidine is an ideal adjuvant drug to propofol during gastrointestinal endoscopy is worthy of our further study.
In the present study, we hypothesized that dexmedetomidine could reduce the median effective concentration (EC50) of TCI propofol during gastrointestinal endoscopy. The primary endpoint was to determine the EC50 of TCI propofol with different doses of dexmedetomidine. The secondary endpoint was to compare the effects of different doses of dexmedetomidine on heart rate (HR) and mean arterial pressure (MAP) during gastrointestinal endoscopy.