The aim of this study is to compare two modes of labour epidural analgesia:

programmed intermittent epidural boluses (PIEB) versus continuous epidural infusion (CEI), with patient controlled epidural analgesia (PCEA), using dexmedetomidine in addition to low-dose bupivacaine and through measuring the total volume of local anesthetic received through patient controlled epidural analgesia per hour

Labour although varies with the individual may be the most painful experience, any women may ever encounter. Concerns about pain in labour are as old as mankind. Pain can make patients feel uncomfortable and become sleepless and agitated. Pain also stimulates the sympathetic nervous system, which causes increase in the heart rate, blood pressure, sweat production, endocrine hyper-function, and delays the patients' prognosis. Labor pain often causes a strong stress response. Several inhalation and parenteral anesthetics, sedatives, tranquilizers, and analgesics have been used for pain relief during labor, while over the last decade, lumbar epidural analgesia has greatly increased. The ideal labor analgesia should be based on maternal and child safety and should have a fast-acting good analgesic effect and less adverse reaction. Different adjuvants such as opioids and α2-adrenergic agonists were added to local anesthetics to improve the quality of intraoperative and postoperative analgesia. 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. It decreases the sympathetic tone with attenuation of the neuroendocrine and hemodynamic response to anesthesia and surgery, reduce anesthetic and opioid requirement, cause sedation and analgesia. Dexmedetomidine was used to enhance the analgesic property of local anesthetics like lidocaine, bupivacaine and ropivacaine. 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. Maintenance of epidural analgesia involved intermittent provider , administered boluses, patient-controlled epidural analgesia, and continuous epidural infusions with or without patient-controlled epidural analgesia. Continuous epidural infusion is the standard application setting for epidural infusion, highly effective, and provides consistent analgesia. however, is associated with greater local anesthetic consumption . A newer approach to maintenance of labor epidural analgesia involves the administration of programmed intermittent epidural boluses with patient-controlled epidural analgesia dosing for breakthrough pain. Earlier studies have suggested that programmed intermittent epidural boluses may be superior to continuous epidural infusion for labor analgesia and may be associated with a reduction in local anesthetic requirement, decreased motor blockade, lower risk of instrumental deliveries, and improved patient satisfaction. This may be related to increased pressure generated during automated boluses, resulting in improved distribution of the local anesthetic in the epidural space .

Inclusion Criteria:

• Age 18 - 45 years
• Scheduled for normal vaginal delivery
• ASA physical status ӀI-IӀӀ.
• Singleton non-complicated pregnancy.
• At least 36 weak of gestation.
• Vertex presentation.

Exclusion Criteria:

• Patient refusal to epidural analgesia.
• History of cardiac, liver, or kidney diseases.
• History of allergy to amide local anesthetics or study medications.
• Any neurological problem.
• History of chronic opioid analgesic use.
• Any contraindication of regional anesthesia.
• Evidence of intrauterine growth restriction or fetal compromise.
• Failed or unsatisfactory analgesic block.
• Body mass index ≥40 kg/m2