Efficacy of Neostigmine Versus Dexamethasone as Adjuvants to Lidocaine During Intravenous Local Anesthesia for Forearm Orthopedic Surgeries

Intravenous regional anesthesia (IVRA) is described firstly in 1908 by August Bier. It is simple, safe, reliable, less cost, efficient method in forearm surgery. The advantage of this method has fast return of motor and sensory function which enables patients for earlier discharge. However, this method has disadvantages such as tourniquet pain, insufficient muscle relaxation and postoperative analgesia.

Lidocaine inhibits action potential propagation within neuronal tissue by binding to receptors in Na+ channels located on the nerve cell membrane. Lidocaine IVRA is safe and effective and is associated with a rapid onset (4.5 minutes) of anesthesia after injection and termination of analgesia (5.8 ± 0.5 minutes) once the tourniquet is deflated.

Neostigmine is a typical cholinesterase inhibitor. It increases the level of acetylcholine (Ach) and indirectly stimulates both nicotinic and muscarinic receptors. In anesthesia, neostigmine is a drug that has been used for reversal of residual neuromuscular block. Administration of neostigmine by intrathecal and epidural routes has been found to cause analgesia by inhibition of the breakdown of Ach in the spinal cord.

Dexamethasone is commonly used in anesthesia to prevent postoperative nausea and vomiting (PONV). Two recent meta-analyses have documented that dexamethasone also reduced postoperative pain and opioid requirement. Intravenous dexamethasone has also been shown to improve postoperative pain control in patients receiving spinal or epidural morphine.

Hong et al reported that intravenous dexamethasone in combination with a caudal block with ropivacaine prolonged the duration of postoperative analgesia without adverse effects in children undergoing orchidopexy. So the investigators expect that addition of dexamethasone or neostigmine will affect duration and postoperative analgesia in bier block.