This randomised, double-blind study compared remifentanil and dexmedetomidine for monitored anaesthesia care (MAC) during minimally invasive corrections of vertebral compression fracture (vertebroplasty (VP) and kyphoplasty (KP)).

In total, 80 ASA physical status I-III patients scheduled for VP and KP randomly received remifentanil or dexmedetomidine to maintain OAA/S scale ≤ 4 during the procedures. Multiple hemodynamic variables of patients were recorded and the frequency of oxygen desaturation, respiratory depression, intraoperative need for other opioids, recovery time, operator satisfaction score, and patients' overall pain experiences were also compared.

The investigators are expecting that both remifentanil and dexmedetomidine appear to be quite safe for MAC during VP and KP. Thus, dexmedetomidine may be an alternative for MAC during VP and KP in elderly patients.

All patients fasted for 8 h before the procedure and were premedicated with midazolam 0.02 mg/kg. In the prone position, patients were monitored by ECG, non-invasive blood pressure, and pulse oximetry, and received supplemental oxygen (3 L/min) via a nasal cannula during the procedure.

Study drugs were prepared in 20 mL and 50 mL syringes to maintain a double-blind design. One anaesthesiologist administered normal saline or dexmedetomidine contained in the 20-mL syringe during the initial 10 min for loading dose of dexmedetomidine. Then, another investigator who did not know which syringes contained remifentanil or dexmedetomidine adjusted the infusion rate with a 50-mL syringe according to patients' response. After all patients in both groups received a bolus dose of propofol 0.3 mg/kg, patients given remifentanil received continuous infusion of the drug at 1-5 µg/kg/h, and patients receiving dexmedetomidine were given that drug at 0.3-0.4 µg/kg over 10 min, followed by continuous infusion of dexmedetomidine 0.2-1 µg/kg/h throughout the procedure. Levels of patient sedation were checked during the procedure and infusion rates of the study drugs were adjusted to maintain alertness/sedation below 4 on the OAA/S scale.

Mean arterial pressure (MAP), heart rate (HR), oxygen saturation (SpO2), respiratory rate (RR), and adverse effects of the study drugs were recorded during the procedure. Ephedrine 5 mg was injected when systolic blood pressure decreased below 90 mmHg. Duration of PACU stay was also recorded.

Operator satisfaction score and patient's overall pain experience were also recorded.

Inclusion Criteria:

• patients who are scheduled for vertebroplasty or kyphoplasty under monitored anesthesia care
• ASA status I-III
• aged more than 65 years old.

Exclusion Criteria:

• obesity (BMI > 30 kg/m2)
• hypotension (systolic blood pressure < 100 mmHg)
• bradycardia (heart rate < 60 bpm)
• heart block
• baseline oxygen desaturation (SpO2 < 90%)
• sleep apnea
• asthma, or chronic obstructive pulmonary disease
• those who refused to give informed consent