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.