Ultrasound-Guided Infraclvicular Block Using Dexmedetomidine Versus Nalbuphine as Adjuvants to Bupivacaine in Upper Limb Orthopedic Surgery

Regional anesthesia is an integral component of modern anesthetic practice. It provides high-quality surgical anesthesia and superior postoperative analgesia while avoiding airway manipulation, minimizing systemic opioid use, and facilitating early ambulation and discharge .

Compared with general anesthesia, regional techniques reduce postoperative pain scores, nausea, and opioid requirements, leading to faster recovery and higher patient satisfaction. They are especially valuable in orthopedic upper-limb surgeries where prolonged postoperative analgesia is desired.

For upper limb procedures, various brachial plexus approaches-interscalene, supraclavicular, infraclavicular, and axillary-are utilized depending on the surgical site. Ultrasound guidance has greatly improved the safety and success rates of these blocks by allowing direct visualization of the nerves, needle, and spread of local anesthetic (LA).

The infraclavicular approach targets the cords of the brachial plexus surrounding the axillary artery in the infraclavicular fossa. It provides dense anesthesia and analgesia for surgeries of the elbow, forearm, and hand. Advantages over the supraclavicular or axillary approaches include reliable blockade of the musculocutaneous, median, ulnar, and radial nerves with a single injection, Lower risk of pneumothorax or phrenic nerve palsy and better catheter stability for continuous analgesia .

Despite these benefits, the main limitation is the finite duration of analgesia when using local anesthetics alone. Adjuvants have been explored to extend block duration and enhance quality without increasing toxicity. Commonly used agents include opioids, clonidine, dexmedetomidine, magnesium sulfate, dexamethasone, and others.

Dexmedetomidine is a highly selective α₂-adrenergic receptor agonist with sedative, anxiolytic, and analgesic properties and minimal respiratory depression.

It acts centrally through activation of α₂ receptors in the locus coeruleus inhibits norepinephrine release, producing sedation (Brummett et al., 2009) , and has peripheral action through hyperpolarization of C and Aδ nerve fibers via inhibition of sodium and potassium channels prolongs the effect of local anesthetics.

The addition of Dexmedetomidine as adjuvant to local bupivacaine in regional anesthesia has proven to : Shortens onset time of sensory and motor block, Prolongs block duration and postoperative analgesia by 3-6 hours, Reduces rescue analgesic consumption, and Provides mild sedation without respiratory depression.

However, potential adverse effects include bradycardia and hypotension related to systemic absorption, particularly at higher doses.

Nalbuphine hydrochloride is a synthetic opioid agonist-antagonist that acts predominantly as a κ-receptor agonist and µ-receptor antagonist. This pharmacologic profile provides potent analgesia with limited risk of respiratory depression, pruritus, or nausea commonly associated with pure µ-agonists such as morphine or fentanyl.

When used as an adjuvant to local anesthetics, nalbuphine is thought to: Prolong sensory and motor block duration, increase postoperative analgesia, Reduce opioid consumption, and has Minimal side effects . it produce its effects through acting on opioid receptors located on peripheral sensory nerve endings and by reducing inflammatory mediator release.