Anesthesia protocol
A total of 90 adult patients were randomly assigned to Group Control (saline solution) ), Group DEX0.5 (0.5 μg/kg dexmedetomidine), or Group DEX1.0 (1.0 μg/kg dexmedetomidine). The gastroenterologists, anesthesiologist and patients, were blinded to the grouping.
Each patient did not receive pre-medication. A 20-G intravenous catheter was inserted into the right or left antecubital region for fluids and medicationsHR, MAP, Electrocardiogram, noninvasive systolic arterial pressure, respiration rate, and peripheral oxygen saturation (SpO2) were monitored (Philips IntelliVue). All patients were given oxygen by nasal catheter (the oxygen flow of 3-5 L/min) during procedure.
A nurse who did not participate in this study diluted the dexmedetomidine solution to 20 mL. After preoxygenation, patients were given different doses of dexmedetomidine: saline solution (Group Control), 0.5 μg/kg dexmedetomidine (Group DEX0.5), or 1.0 μg/kg dexmedetomidine (Group DEX1.0). The same volume (20 mL) of dexmedetomidine solutions or saline solution was administered in 5 min. Then, propofol was given by Graseby 3500 TCI Syringe Pump with the Marsh parameters. The plasma target-controlled concentration of the first patient for each group was 2.5 μg/mL. Once the target concentration on the TCI pump was achieved, gastroenterologists started gastroscopy. In our endoscopy center, patients underwent gastroscopy followed by colonoscopy in one anaesthetic treatment. Target-controlled infusion of propofol is maintained until the end of colonoscopy. A stable sedation without patient body movements is necessary to enhance the precision and swiftness of the gastrointestinal endoscopy and enhance the patient satisfaction and the gastroenterologist satisfaction. The flow chart of the Dixon’s up-and-down methodology was shown in Figure 7. Whether the patients were “responsive” is determined by the anesthesiologist who does not know the grouping and dexmedetomidine dose (saline solution). .
Emergency equipment was always on standby. Ephedrine 6-10 mg was administered in case MAP dropped blow 60 mmHg or 30% less than the baseline, and atropine 0.25 mg was given in case HR were lower than 50 beats per minute. Appropriate nitroglycerin was administered in case MAP were over 120 mmHg. If SpO2 < 92% for more than 5 seconds, ventilation support was performed by the anesthesiologist when necessary.