Background and objectives: The fixed-rate continuous background infusion mode with bolus dosing is a common modality for intravenous patient-controlled analgesia (PCA). However, some patients suffer from inadequate analgesia or opioid-related adverse effects due to the biphasic pattern of postoperative pain. Therefore, we investigated the postoperative analgesic efficacy of PCA using an optimizing background infusion mode (OBIM) where the background injection rate varies depending on the patient's bolus demand. Materials and Methods: We prospectively enrolled 204 patients who underwent laparoscopic cholecystectomy in a randomized, controlled, double-blind study. Patients were allocated to either the optimizing (group OBIM) or the traditional background infusion group (group TBIM). The numeric rating scale (NRS) score for pain was evaluated at admission to and discharge from the recovery room, as well as at the 6th, 24th, and 48th postoperative hours. Data on bolus demand count, total infused volume, and background infusion rate were downloaded from the PCA device at 30-min intervals until the 48th postoperative hour. Results: The NRS score was not significantly different between groups throughout the postoperative period (p = 0.621), decreasing with time in both groups (p < 0.001). The bolus demand count was not significantly different between groups throughout (p = 0.756). The mean total cumulative infused PCA volume was lower in group OBIM (84.0 (95% confidence interval: 78.9-89.1) mL) than in group TBIM (102 (97.8-106.0) mL; p < 0.001). The total cumulative opioid dose in fentanyl equivalents, after converting sufentanil to fentanyl using an equipotential dose ratio, was lower in group OBIM (714.1 (647.4-780.9) μg) than in group TBIM (963.7 (870.5-1056.9) μg); p < 0.001). The background infusion rate was significantly different between groups throughout the study period (p < 0.001); it was higher in group OBIM than in group TBIM before the 12th postoperative hour and lower from the 18th to the 48th postoperative hour. Conclusions: The OBIM combined with bolus dosing reduces the cumulative PCA volume and opioid consumption compared to the TBIM combined with bolus dosing, while yielding comparable postoperative analgesia and bolus demand in patients undergoing laparoscopic cholecystectomy.
Keywords: background infusion; intravenous infusions; laparoscopic cholecystectomy; opioid analgesics; patient-controlled analgesia; postoperative pain.