Comparison: Constant-rate Infusion Plus Demanding Dosing VS Variable-rate Feedback Infusion Plus Demanding Dosing

The PCA regimen consisted of fentanyl 20 μg/kg and Ramosetron Hcl 0.3 mg (total volume including saline: 100 ml) and was programmed to deliver 1 ml /h as a background infusion and a bolus of 1.5 ml on-demand, with a 15 min lockout time. It can increment or decrement rate(0.2ml/hr) by press bolus button during a 48 h period

The PCA regimen consisted of fentanyl 20 μg/kg and Ramosetron Hcl 0.3 mg (total volume including saline: 100 ml) and was programmed to deliver 1 ml /h as a background infusion and a bolus of 1.5 ml on-demand, with a 15 min lockout time during a 48 h period