Abstract
Intraoperative administration of opioids is important for postoperative pain management by using patient-controlled analgesia (PCA) . For successful postoperative pain management, the effect-site concentrations of opioids such as morphine and fentanyl have to reach minimum effective analgesic concentration (MEAC) before the patient wakes up from general anesthesia.
Postoperative MEAC of morphine is estimated to be 30 ng/ml. To maintain the effect-site concentration of morphine at 30 ng/ml at the end of general anesthesia, 0.2 mg/kg of morphine should be administered approximately 30 minutes before the end of general anesthesia.
The postoperative MEAC of fentanyl is estimated to be 1 ng/ml. The effect-site concentration of fentanyl can be maintained at approximately 1 ng/ml by intraoperative loading administration of fentanyl, i.e., 3 injections of 2μg/kg of fentanyl at 30-minute intervals and continuous administration of 0.5μg/kg/hr of fentanyl, 3 hours before the end of general anesthesia.
