Objective: To analyze the causes of excessive residual volume (≥ 100 mL) upon removal of patient‑controlled analgesia (PCA) pumps in patients undergoing lower abdominal surgery under an intelligent closed‑loop management model, and to provide evidence for optimizing analgesic regimens and drug management. Methods: A retrospective survey was conducted among 292 eligible patients from September 2022 to August 2023. Data on departmental distribution, timing of pump removal, adverse reactions, and antiemetic addition were collected. Results: Among the 292 patients, gastrointestinal surgery accounted for 78.42%. Pump removal was concentrated on postoperative days 3–4 (51% combined). The most prevalent adverse reactions were poor sleep (28.42%), nausea (19.86%), and non‑pain complaints (23.96%). Notably, 97.94% of PCA pumps were prescribed without antiemetics. Conclusion: Postoperative nausea and vomiting, non‑pain discomfort, and sleep disturbances are key surface manifestations leading to premature pump discontinuation or clamping, resulting in residual drug volume. The insufficient addition of antiemetics and the urgent need for training in adverse reaction differentiation within the intelligent closed‑loop management system require immediate attention.