Effectiveness and safety of nurse-led different epidural analgesia methods based on symptom management theory in patients with severe acute pancreatitis: A single-center RCT protocol - You Yuan; Qian Luo; Feiyu Yan; Li Li; Lifeng He; Yan Zhou; Chunlan Wu; Mingli Zhong; Fang Chen; Xia Zhang; Junxi Chen; Bao Fu; et al. (PLoS ONE, 2026)