2. Presence of contraindications to epidural analgesia, which includes: (1) History of infectious disease of the central nervous system (poliomyelitis, cerebrospinal meningitis, encephalitis, etc.); (2) History of spinal or intra-spinal disease (trauma or surgery of spinal column, intra-spinal canal mass, etc.); (3) Systemic infection (sepsis); (4) Skin or soft tissue infection at the site of epidural puncture; (5) Coagulopathy.