What sedatives can be administered to supplement a regional anesthetic?
The best anxiolytic may be a solid relationship between the anesthesiologist and patient; however, excellent rap-port may be difficult to establish within the confines of a fast-paced ambulatory surgery center. It has been shown that a preoperative visit with the anesthesiologist immedi-ately before surgery may serve as a powerful anxiolytic itself.
In the pharmacologic realm, intravenous midazolam has proven to have excellent sedative and anxiolytic prop-erties (Table 77.1). It is water-soluble, nonirritating to veins, painless on administration, provides superb amnesia with rapid onset, and it is therefore well accepted by patients. Diazepam can cause significant discomfort on intravenous infusion, and if patients are followed for a number of days after injection it has been shown to cause thrombophlebitis in a significant number of cases. Therefore, intravenous diazepam has been virtually elimi-nated from the practice of anesthesia. Compared with diazepam, midazolam’s much shorter elimination half-life of 1–4 hours provides a significantly shorter time to recovery. Midazolam is best titrated every 2 minutes in 1- to 2-mg increments, because its onset is rapid and effects may be profound. Sedation after small-to-moderate intravenous doses usually lasts approximately 20–30 minutes. The pro-found amnestic properties may interfere with assimilating and following instructions, and patients may become unable to cooperate during surgery. Some patients who receive the drug may become completely disoriented, uncooperative, or even combative. This may necessitate either increasing the depth of sedation, pharmacologic reversal, or conver-sion to a general anesthetic.
Remifentanil is an excellent addition for the patient who requires a short-acting opioid to provide analgesia either during the performance of a painful block or to provide adjunctive analgesia during an inadequate block. It can be administered by intravenous bolus or by continuous infusion. Bolus doses of 0.5 μg/kg may be administered with repeat doses titrated to desired effect. For a continuous infusion, the dose ranges from 0.02 to 0.3 μg/kg/min. Side-effects common to all drugs in the opioid class include nau-sea, vomiting, and the potential for significant respiratory depression. Alternatively, fentanyl administered in intra-venous bolus doses of 25–50 μg can be employed to provide adjunctive analgesia. Instead of using a benzodiazepine to provide sedation, propofol can be administered by either bolus dose (10–20 mg) or continuous infusion (0.1–0.2 mg/kg/min) and titrated to the desired hypnotic effect. Inherent anti-nausea and anti-emetic properties of propo-fol provide a significant advantage in the ambulatory setting.