Background and Objectives Patients treated with regional anesthesia often require concomitant medication for comfort and sedation. Propofol is widely used for this purpose. Remifentanil, a new ultra-short-acting opioid, exhibits at low doses distinct sedative properties that may be useful for supplementation of regional anesthesia. This study compared the effectiveness of remifentanil and propofol infusions for providing sedation during regional block placement and surgery.

Methods In an open, prospective trial, 28 patients were randomly allocated to receive continuous infusions of remifentanil (6 μg/kg/h) or propofol (3 mg/kg/h) for sedation during spinal or axillary regional anesthesia. Infusion rates were titrated to maintain a sedation level ≥ 2 as assessed with the Observer's Assessment of Alertness Scale. Vital signs were measured continuously, during and for 2 hours after ending study drug infusion.

Results Similar scores for comfort and sedation were obtained in both groups during placement of the regional block and during surgery. Degree of sedation correlated with drug infusion rate of remifentanil (P < .002) but not for propofol. Respiratory rate decreased in the remifentanil group in absence of surgery (P < .05). Mean arterial pressure and heart rate were 20% lower in the propofol group (P < .05). Return to alertness occurred after 10 ± 6 minutes in the remifentanil group and after 16 ± 15 minutes in the propofol group. Similar incidences of hypotension, bradycardia, and nausea and vomiting were found in both groups, but intraoperative respiratory depression and nausea were more prominent in the remifentanil group.

Conclusions When titrated to the same sedation level, remifentanil provided a smoother hemodynamic profile than propofol during regional anesthesia. The frequent occurrence of remifentanil-induced respiratory depression requires cautious administration of this agent. The incidence of adverse reactions seen with both agents during and after their administration makes the management of such sedative infusion techniques difficult.