A Prospective, Randomized Trial Comparing Hydromorphone and Nalbuphine for Postcesarean Patient-Controlled Analgesia and Developing a Risk Prediction Model for Inadequate Analgesia

Kaiwen Zhang,1,* Jiaoli Sun,1,* Caixia Zhang,2 Bo Jiao,1 Wencui Zhang,1 Shangchen Yu,1 Xueqin Cao,1 Zhiqiang Zhou,1 Guanglei Zhang,1 Xianwei Zhang1 1Department of Anesthesiology and Pain Medicine,Hubei Key Laboratory of Geriatric Anesthesia and Perioperative Brain Health, and Wuhan Clinical Research Center for Geriatric Anesthesia, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China; 2Department of Anesthesiology, Wuhan No. 1 Hospital, Wuhan, People’s Republic of China*These authors contributed equally to this workCorrespondence: Guanglei Zhang, Department of Anesthesiology and Pain Medicine, Hubei Key Laboratory of Geriatric Anesthesia and Perioperative Brain Health, and Wuhan Clinical Research Center for Geriatric Anesthesia, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095 Jiefang Avenue, Qiaokou District, Wuhan, Hubei Province, 430030, People’s Republic of China, Email zsytd528@163.com Xianwei Zhang, Department of Anesthesiology and Pain Medicine, Hubei Key Laboratory of Geriatric Anesthesia and Perioperative Brain Health, and Wuhan Clinical Research Center for Geriatric Anesthesia, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095 Jiefang Avenue, Qiaokou District, Wuhan, Hubei Province, 430030, People’s Republic of China, Email ourpain@163.comPurpose: Effective postoperative analgesia is essential for maternal recovery following cesarean delivery. Hydromorphone and nalbuphine are commonly used opioids with differing pharmacologic properties, but direct comparisons in postcesarean patient-controlled analgesia (PCA) are limited. This study aimed to compare the analgesic efficacy and safety of hydromorphone versus nalbuphine and to develop a predictive model for inadequate analgesia.Patients and Methods: In this prospective, randomized, double-blind clinical trial conducted from December 2024 to March 2025, 212 women undergoing elective cesarean section under spinal anesthesia were randomized (1:1) to receive hydromorphone (0.1 mg/mL) or nalbuphine (1 mg/mL) via standardized intravenous PCA. The primary outcome was the incidence of inadequate analgesia within 24 hours, defined as a numerical rating scale (NRS) score ≥ 4 at rest or during movement. Secondary outcomes included adverse events, PCA consumption, and recovery indicators. Multivariable logistic regression was used to identify predictors of inadequate analgesia, and a nomogram was constructed and internally validated.Results: Nalbuphine was associated with a significantly lower incidence of inadequate analgesia than hydromorphone (14.2% vs 26.4%; P = 0.026), as well as reduced nausea and vomiting (18.9% vs 32.1%; P = 0.001) and pruritus (0% vs 5.7%; P = 0.029). Independent predictors of inadequate analgesia included PCA regimen (OR, 0.30; P = 0.026), gestational diabetes mellitus (OR, 4.40; P = 0.007), blood type AB (OR, 3.80; P = 0.043), and preoperative anxiety (OR, 0.20; P = 0.044). The predictive model showed good discrimination (AUC = 0.754).Conclusion: Nalbuphine demonstrated superior analgesia and fewer adverse effects compared with hydromorphone for postcesarean PCA. The developed predictive model may support individualized pain management by identifying patients at risk for inadequate analgesia.Keywords: postoperative analgesia, patient-controlled analgesia, hydromorphone, nalbuphine, predictive model