- IV PCA with oxycodone is started after the administration of loading dose. A semi-electronic pump (Automed 3200; Ace Medical, Seoul, South Korea) is used for PCA with demand bolus of 1 ml, background infusion of 1 ml/h and lock-out time of 15 min. The concentration of oxycodone in IV PCA bag is 1 mg/ml, and the volume of oxycodone-normal saline mixture delivered to patients for approximately 4 days is 200 ml.