Sufentanil-ropivacaine combination is commonly used for epidural labor anesthesia, but is associated with some adverse events. Dexmedetomidine and esketamine, each has been effectively used for neuraxial anesthesia in combination with local anesthetics. Plenty of evidences show that both dexmedetomidine and esketamine, combined with ropivacaine, are also effective as the sufentanil-ropivacaine combination when used for epidural labor analgesia. This pilot trial is designed to evaluate the efficacy and safety of the dexmedetomidine-esketamine-ropivacaine versus sufentanil-ropivacaine combination for epidural labor analgesia, and to test the feasibility of a future large randomized trial.

Sufentanil-ropivacaine combination is commonly used for epidural labor anesthesia, but is associated with some adverse events. Dexmedetomidine and esketamine, each has been effectively used for neuraxial anesthesia in combination with local anesthetics. Plenty of evidences show that both dexmedetomidine and esketamine, combined with ropivacaine, are also effective as the sufentanil-ropivacaine combination when used for epidural labor analgesia.

The investigators hypothesize that the dexmedetomidine-esketamine-ropivacaine combination, by avoiding sufentanil and decreasing ropivacaine concentration, may provide non-inferior analgesia with less harmful effect on neonatal outcomes when compared with the sufentanil-ropivacaine combination. This pilot trial is designed to evaluate the efficacy and safety of the dexmedetomidine-esketamine-ropivacaine versus sufentanil-ropivacaine combination for epidural labor analgesia, and to test the feasibility of a future large randomized trial.

Inclusion Criteria:

1. Aged 18 years or above;
2. Single term cephalic pregnancy preparing for vaginal delivery;
3. Agreed to receive epidural labor analgesia.

Exclusion Criteria:

1. History of schizophrenia or epilepsy;
2. Presence of contraindications for epidural analgesia, including: (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.
3. Relative contraindications for the use of dexmedetomidine, including prenatal bradycardia (HR<60 beats per minute) and second-degree or higher atrioventricular block;
4. Relative contraindications for the use of esketamine, including uncontrolled hypertension (systolic blood pressure >180 mmHg) and hyperthyroidism;
5. Not well controlled systemic diseases, including heart disease, liver disease, kidney disease, or an ASA classification >III;
6. Other conditions that are considered unsuitable for study participation.

Pregnant women preparing for vaginal delivery.