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Regional anesthesia has become more popular in cesarean deliveries because most of the
parturients prefer being awake during the birth process. In addition, regional anesthesia may
be a safer method than general. In spinal anesthesia local anesthetics alone may not be
enough for an effective postoperative analgesia and hemodynamic stability of the patient wich
is crucial during cesarean section. So far many adjuvants have been used to augment the
analgesia produced by intrathecal local anesthetics and to reduce their adverse effects .

Various intrathecal adjuvants to local anaesthetics have found to improve the quality and
extend duration of spinal block. Prolongation of duration of spinal block is desirable both
for long procedures and for postoperative pain relief. Efficacy and safty of intrathecal
magnesium as analgesic adjuvant has been tested by several clinical trails in recent
years.Antinociceptive effect of magnesium appears to be relevant for the management of
chronic and post operative pain. These effects are primarily based on regulation of calcium
influx in to the cell. Magnesium blocks calcium influx and non competitively antagonizes NMDA
channels. NMDA receptor signelling plays an impartent in determining the duration of acute
pain3).) addition of magnesium to spinal anaesthesia improved postoperative analgesia in
orthopedic setting. addition of intrathecal magnesium sulfate to 10 mg bupivacaine plus 25µg
fentanyl prolonged spinal anaesthesia in patients undergoing lower extremity surgery.

Dexmedetomidine is a highly selective 2-adrenergic agonist which has been used as
pre-medication and as an adjuvant to general anesthesia.Dexmedetomidine have several
beneficial actions during perioperative period. They decrease sympathetic tone with
attenuation of the neuroendocrine and haemodynamic response to anaesthesia and surgery,
reduce anaesthetic and opiod requirement, cause sedation and analgesia. Dexmedetomidine was
first introduced into clinical practice as a short term intravenous sedative in intensive
care. Like any other adjuvant dexmedetomidine is not free from adverse effects. Use of
dexmedetomidine is often associated with a decrease in heart rate and blood
pressure.Dexmedetomidine was used to enhance the analgesic property of local anaesthetics
like lidocaine bupivacaine and ropivacaine. In vivo and in vitro studies indicated that these
local anaesthetics had significant neurotoxicity. Dexmedetomidine showed protective or growth
promoting properties in tissues, including nerve cells from cortex. Intrathecal
dexmedetomidine has a neuroprotective effect similar to methylprednisolone.

The mechanism by which intrathecal alpha 2-adrenergic agonists prolong the motor and sensory
block of local anesthetics is not clear. It may be an additive or synergistic effect
secondary to the different mechanisms of action of local anesthetic and alpha 2 adrenergic
agonist. The local anesthetics act by blocking sodium channels, whereas the alpha 2
adrenergic agonist acts by binding to pre synapyic C fibre and post synaptic dorsal horn
neurons. Intrathecal alpha 2 adrenergic agonist produce analgesia by depressing the realease
of C fibre transmission by hyperpolarization of post synaptic dorsal horn neurons. Li et al
observed that Glutamate is involved in excitatory neurotransmission nociception and plays an
essential role in relaying noxious stimuli in the spinal cord. Intrathecal injection of alpha
2 adrenergic agonists produces potent antinociceptive effects by altering spinal
neurotransmitter release and effectively treats acute pain.