Randomization and blinding
Participants who gave their consent for the study were randomly assigned to one of four groups using a computer-generated list of random numbers with a 1:1:1:1 ratio. Before the incision was closed, 30 ml of study drugs were injected into the skin, subcutaneous tissue and paraspinal muscle.Here are the different groups and their respective solutions:Group R: 15 mL of ropivacaine 1% mixed with 15 mL of NS (normal saline).Group R + DXM: 15 mL of ropivacaine 1% mixed with 10 mg of dexamethasone in 15 mL NS.Group R + DEX: 15 mL of ropivacaine 1% mixed with 1 µg/kg of dexmedetomidine in 15 mL NS.Group R + DXM + DEX: 15 mL of ropivacaine 1% mixed with 10 mg of dexamethasone and perineural dexmedetomidine 1 µg/kg in 15 mL NS.All patients did not take dexmedetomidine or dexamethasone before and after surgery. The randomization tables were kept in the hospital pharmacy, and a nurse who was not involved in the study prepared the study medication and the patient-controlled anesthesia (PCA) solution. The group assignments were kept blinded from the patients, surgeons, anesthesiologists and researchers who collected the data.