Beyond opioid dosage: temporal dynamics of intravenous patient-controlled analgesia use captured by electronic device logs—a post hoc analysis of three randomized controlled trials

Background: Intravenous patient-controlled analgesia (IV-PCA) is widely used for postoperative pain management.However, its temporal usage pattern remains poorly characterized.Methods: This secondary analysis included 332 patients from three randomized controlled trials investigating postoperative analgesia following robot-assisted laparoscopic prostatectomy, video-assisted thoracoscopic surgery, and minimally invasive distal gastrectomy (MIDG).Each trial compared two analgesic strategies, yielding six groups.Only the conventional MIDG group received IV-PCA alone without multimodal analgesia.Hourly fentanyl-based IV-PCA consumption and bolus attempts were obtained from electronic device logs.The primary outcome was the first time when 75% of patients reached an hourly IV-PCA consumption of ≤ 20 µg fentanyl/hr, predefined as the lowutilization threshold.The secondary outcomes included the first time when 75% of patients reached a bolus attempt rate ≤ 1/hr, temporal trajectories of PCA use, delivery-to-demand ratio, and correlations between pain scores and cumulative opioid consumption.Results: The low-utilization threshold was reached within 6-8 hours by 75% of patients in all groups, except for the conventional MIDG group.Similarly, bolus attempts declined to ≤ 1/hr after 7-9 hours postoperatively, again excluding the opioid-only group.Delivery-to-demand ratio was the lowest immediately after surgery and increased over time, showing higher values with multimodal analgesia.Pain intensity correlated significantly, but only weakly, with PCA consumption (r = 0.16-0.24,P < 0.05 for all comparisons).Conclusions: Fentanyl-based IV-PCA use declined rapidly, indicating that its benefit is largely confined to the early postoperative phase and that its duration can be shortened when multimodal analgesia is well established.