Remifentanil Administration During Monitored Anesthesia Care

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Abstract
This randomized, double-blind study was designed to evaluate the analgesic effectiveness and respiratory stability of remifentanil when administered as intermittent bolus injections, a variable-rate infusion, or a combination of a constant basal infusion supplemented with intermittent boluses during monitored anesthesia care (MAC). Forty-five patients undergoing extracorporeal shock wave lithotripsy (ESWL) procedures were randomly assigned to one of the three modes of remifentanil administration. All patients received midazolam 2 mg IV, followed by a propofol infusion at 50 [micro sign]g [center dot] kg-1 [center dot] min-1. Two minutes before administering a series of test shock waves: Group I received a remifentanil infusion of 0.1 [micro sign]g [center dot] kg-1 [center dot] min-1, and a saline bolus (5 mL); Group II received a saline infusion and a remifentanil bolus (25 [micro sign]g in 5 mL); and Group III received a remifentanil infusion of 0.05 [micro sign]g [center dot] kg-1 [center dot] min-1, and a remifentanil bolus (12.5 [micro sign]g in 5 mL). The average pain intensity was scored on an 11-point scale, with 0 = no pain to 10 = severe pain. During the ESWL procedure, pain was treated by increasing the study drug infusion rate by 25%-50% and administering 5-mL bolus injections of the study medication in Groups I (saline) and II (remifentanil 25 [micro sign]g). In Group III, intermittent 5-mL boluses (remifentanil 12.5 [micro sign]g) were administered as needed. Patients in Groups II and III reported lower pain scores in response to the test shocks. Significantly more remifentanil was administered in Group I (379 +/- 207 [micro sign]g) than in Group II (201 +/- 136 [micro sign]g). However, more interventions were required for the treatment of intraoperative pain in the intermittent bolus group (Group II). When remifentanil is administered as the analgesic component of a MAC technique, these data support the use of intermittent bolus doses (12.5-25 [micro sign]g) alone or in combination with a basal infusion (0.05 [micro sign]g [center dot] kg-1 [center dot] min-1) as alternatives to a variable-rate continuous infusion. Implications: In this study, three different modes of remifentanil administration were used during monitored anesthesia care for extracorporeal shock wave lithotripsy procedures. These results suggest that using intermittent bolus injections of remifentanil (25 [micro sign]g) or a continuous infusion (0.05 [micro sign]g [center dot] kg-1 [center dot] min-1) supplemented with intermittent bolus (12.5 [micro sign]g) injections may be more effective than a variable-rate infusion of remifentanil during propofol sedation. (Anesth Analg 1999;88:518-22)