Target-Controlled Infusion of Alfentanil for Conscious Sedation

Cho, Duk Hyun; Kim, Dong Hee

Abstract

BACKGROUND: Opioids are frequently used to relieve pain or to induce sedation during monitored anesthesia care and regional anesthesia. Infusion rates for alfentanil range from 0.25-0.72 microgram/kg/min. This study was performed to define the optimal range of blood concentration of alfentanil to produce a conscious sedation without significant vital sign changes and side effects in spinal anesthesia patients.
METHODS
One hundred patients were administered spinal anesthesia with 0.5% hyperbaric bupivacaine 12-18 mg and then a target controlled infusion (TCI) of alfentanil using a syringe pump equiped with a stelpump program. The target concentrations of alfentanil were 20 ng/ml (n = 20, group A20), 25 ng/ml (n = 20, group A25), 30 ng/ml (n = 20, group A30), 35 ng/ml (n = 20, group A35) and 40 ng/ml (n = 20, group A40). Sedation scale, bispectral index (BIS), systolic and diastolic blood pressure, heart rate, SpO2, and anxiety score were checked during the operation and postoperatively one hour later in the recovery room.
RESULTS
The sedation scale was significantly higher in groups A30, A35, and A40 than in the other two groups (P < 0.05), but there were no significant difference in BIS among the groups. Mean infusion rates of alfentanil were 0.27-0.46 microgram/kg/min. Time from end of alfentanil infusion to response to a verbal command was significant delayed in groups A30, A35, and A40 than in the other two groups. Recall of operative procedure occurred in 50 65%. Intraoperative hypotension, bradycardia, and respiratory depression occurred more frequently in groups A35, and A40 than in the other three groups (P < 0.05). Incidences of postoperative nausea and vomiting were significantly higher in groups A35, and A40 than in the other three groups (P < 0.05). Heart rate and systolic and diastolic pressures were more significantly lowered during the operation in groups A35, and A40 than in the other three groups (P < 0.05).
CONCLUSIONS
Alfentanil has an effective sedation effect at 40% of the analgesic dosage during spinal anesthesia. But, incidences of side effects, like hypotension, bradycardia, and nausea and vomiting increased with alfentanil target concentrations. TCI of alfentanil at 30 ng/ml produces effective sedation, antianxiety effect, and fewer side effects during spinal anesthesia.