A comparison of 2 intravenous patient-controlled analgesia modes after spinal fusion surgery: Constant-rate background infusion versus variable-rate feedback infusion, a randomized controlled trial

BACKGROUND: Conventional intravenous patient-controlled analgesia (PCA), which usually involves constant-rate background infusion plus demand dosing, may cause adverse effects or insufficient analgesia. When variable-rate feedback infusion plus demand dosing mode is used, the infusion rate can be changed according to the patient's needs. METHODS: In this prospective randomized double-blind study, 78 adults who were undergoing spinal fusion surgery were randomly allocated to either the constant-rate background infusion plus demand dosing group (group C) or the variable-rate feedback infusion plus demand dosing group (group V). The number of demands, volume delivered, numerical rating scale (NRS) score, adverse effects and the use of rescue analgesics were examined at 30 minutes after the operation in the post-anesthesia care unit, and at 6, 12, 24, and 48 hours. RESULTS: The number of demands was significantly lower in group V than in group C at 12-24 hours (4.59 ± 4.31 vs 9.21 ± 6.79 times, P = .001) and over the total period. The volume delivered via PCA was significantly lower in group V than in group C at 12 to 24 hours (13.96 ± 13.45 vs 21.19 ± 8.66 mL, P = .006), 24 to 48 hours (13.39 ± 12.44 vs 33.6 ± 12.49 mL, P = .000), and over the total period. NRS scores, administration of rescue analgesics, and postoperative nausea and vomiting showed no between-group differences. CONCLUSIONS: Variable-rate feedback infusion plus the demand dosing mode can control postoperative pain more efficiently, with lower dosages of analgesics, than constant-rate background infusion plus demand dosing in patients who undergo spinal fusion surgery.