Dexamethasone vs Dexmedetomidine vs Combination as Adjuvants to Popliteal Sciatic Nerve Block in Children

A Randomized, Double-Blinded, Controlled Trial Comparing Perineural Dexamethasone, Dexmedetomidine, and Their Combination as Adjuvants to Ropivacaine for Popliteal Sciatic Nerve Block in Pediatric Patients

This clinical study will evaluate three commonly used medications that can be added to local anesthetic during a popliteal sciatic nerve block in children undergoing surgery of the lower leg or foot. These medications-dexamethasone, dexmedetomidine, or a combination of both-may help the nerve block last longer and provide better postoperative pain control.

All participating children will receive a standard popliteal sciatic nerve block with ropivacaine, a commonly used local anesthetic. They will then be randomly assigned to one of three groups: (1) ropivacaine with dexamethasone, (2) ropivacaine with dexmedetomidine, or (3) ropivacaine with both dexamethasone and dexmedetomidine. Neither the children, parents, nor the clinical staff assessing pain will know which medication was given.

The goal of this study is to determine whether the combination of dexamethasone and dexmedetomidine provides longer pain relief and reduces the need for additional pain medication compared with either medication alone. The results may help identify the most effective and safest strategy for improving postoperative comfort in pediatric patients receiving regional anesthesia.

Popliteal sciatic nerve block is frequently used in pediatric anesthesia to provide effective pain control for surgical procedures involving the lower leg, ankle, and foot. Although ropivacaine alone offers good analgesia, its duration is limited, and additional medications (adjuvants) are often added to prolong the effect of the block. Two commonly used adjuvants are dexamethasone, a corticosteroid, and dexmedetomidine, an alpha-2 adrenergic agonist. Each of these medications has been shown to extend the duration of analgesia, but it remains unclear whether combining them provides an additive or potentially synergistic benefit.

This randomized, double-blinded, controlled clinical trial will compare three perineural adjuvant strategies: dexamethasone, dexmedetomidine, and their combination. All participants will receive a single-shot popliteal sciatic nerve block with 0.2% ropivacaine. Children will then be randomized into one of three treatment arms:

1. ropivacaine with perineural dexamethasone,
2. ropivacaine with perineural dexmedetomidine, or
3. ropivacaine with a perineural combination of dexamethasone and dexmedetomidine. Pain scores, block duration, opioid use, and recovery parameters will be assessed by trained observers who are blinded to group assignment. The primary aim is to determine whether the combination of dexamethasone and dexmedetomidine leads to superior analgesia compared with either drug alone. Secondary aims include evaluating the time to first rescue analgesia, total postoperative opioid requirements, behavioral pain scores (e.g., FLACC), adverse events, and early functional recovery.

This study seeks to provide high-quality evidence to guide the optimal choice of perineural adjuvants in pediatric regional anesthesia and may help establish best-practice recommendations for improving postoperative comfort and safety in children undergoing lower-limb surgery.

Inclusion Criteria:

• Children aged 3 to 12 years.
• Scheduled for elective unilateral lower limb surgery (foot, ankle, or distal lower leg) under general anesthesia with a popliteal sciatic nerve block planned for postoperative analgesia.
• ASA physical status I-III.
• Ability of parents or legal guardians to understand the study procedures and provide written informed consent.
• Child and parents/guardians available for telephone follow-up at 1 week and 1 month after surgery.

Exclusion Criteria:

• Refusal of the parents/legal guardians to provide informed consent or refusal of the child to cooperate with anesthesia or study procedures.
• Known allergy or hypersensitivity to ropivacaine, dexamethasone, dexmedetomidine, or any component of the study medications.
• Pre-existing neurological deficit or neuromuscular disease affecting the lower limbs (motor or sensory).
• Coagulopathy or current therapeutic anticoagulation that contraindicates regional anesthesia.
• Local infection, inflammation, or skin lesions at the planned block site.
• Severe cardiac, hepatic, renal, or respiratory disease that, in the investigator's opinion, increases the risk of study participation.
• History of clinically significant arrhythmias, severe bradycardia, or second/third degree atrioventricular block not treated with a pacemaker.
• Developmental delay or severe cognitive impairment that precludes reliable pain assessment or follow-up.
• Chronic use of opioid analgesics or sedatives (≥ 2 weeks of daily use before surgery).
• Participation in another interventional clinical trial within the last 30 days.
• Any other condition considered by the investigator to interfere with protocol adherence, safety monitoring, or reliable outcome assessment.