Evaluation of the Analgesic Effect of Dexmedetomidine Versus Fentanyl as Adjuvants to Epidural Bupivacaine in Patients Undergoing Lumbar Spine Surgeries

Relieving post-operative pain of spine surgeries has become an indispensable component in anesthesiology. Various methods have been tried for the management of post-operative pain in spine surgeries out of which regional techniques are becoming most promising. The quality of regional anesthesia has been reported to improve with the addition of opioids (such as morphine, fentanyl, and sufentanil) and other drugs (such as dexmedetomidine, clonidine, magnesium sulfate, neostigmine, ketamine, and midazolam), but no drug to inhibit nociception is without associated adverse effects . α2 adrenergic agonists have both analgesic and sedative properties when used as an adjuvant in regional anesthesia. Dexmedetomidine is an S-enantiomer of medetomidine with a higher specificity for α2-adrenoreceptor (α2 : α1, 1620 : 1) compared to clonidine (α2 : α1, 220 : 1). It was first introduced into practical use as intravenous sedative after the approval of U.S. Food and Drug Administration in 1999. Since then it has been investigated as the anxiolytic, sympatholytic, and analgesic properties related to α2-adrenoceptor binding, and it is now being used as a co-analgesic drug. As adjuvant, neuroaxial administration is the appropriate route to dexmedetomidine, because the analgesic effect of α2-agonists mostly occurs at spinal level, and dexmedetomidin's high lipophilicity facilitates rapid absorption into the cerebrospinal fluid and binding to the spinal cord α2-adrenoreceptor. regional-administeration of dexmedetomidine has been shown to exert potent antinociceptive effects in animals. To date, a few studies have reported on the effects of epidural dexmedetomidine combined with local anesthetics in humans. . Administration of an α2-agonist via an intrathecal or epidural route provides an analgesic effect in postoperative pain without severe sedation. This effect is due to the sparing of supraspinal CNS sites from excessive drug exposure, resulting in robust analgesia without heavy sedation . The adverse effects of dexmedetomidine include hypotension, hypertension, nausea, bradycardia, atrial fibrillation, and hypoxia. Fentanyl is one of the short-acting narcotic analgesics with potent morphine-like action . Neuroaxial administration of lipophilic opioids such as Fentanyl and sufentanyl tends to provide a rapid onset of analgesia. Their rapid clearance from cerebrospinal fluid may limit cephalic spread and the development of certain side effects such as delayed respiratory depression