Pain level and amount of opioid consumption (determined using the intravenous PCA pump) were recorded to evaluate the analgesic effect. Pain levels during the four periods were estimated using a VAS that ranged from 0 (no pain) to 10 (worst imaginable pain) during each of the four study periods. Opioid (fentanyl) consumption was recorded for each of the four periods and summed to obtain consumption during the entire72-hour study period.