الفهرس 
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Abstract
The most unpleasant consequence of surgeries is postoperative pain, which if improperly treated, can delay recovery and lengthen hospital stays. It’s still challenging to manage postoperative pain effectively.
Epidural analgesia is one of the most effective analgesic strategies for the majority of abdominal surgeries. Although usage of epidural opioids promotes the analgesia, but it produces annoying side effects. The use of dexmedetomidine as adjuvant in regional analgesia is increasing nowadays because of its potent analgesic action and its anesthetic sparing effect with less frequent side effects when compared to epidural opioids.
Dexmedetomidine as an alpha 2 adrenergic receptor agonist stimulates central presynaptic α2 receptors resulting in decreased central sympathetic outflow and noradrenaline release which in turn leads to hypotension, bradycardia, sedation and anxiolysis. It has an analgesic action via action on pre- and postsynaptic α2 receptors. On the other hand, fentanyl acts primarily as agonist at μ-opioid receptors to enhance analgesia. It acts either directly on the spinal nerve or by penetrating the dura to act at the primary afferent tissues which contain opioid-binding sites.
The current study compared the postoperative analgesic effects of an epidural mixture of bupivacaine with either dexmedetomidine or fentanyl. Seventy five adult patients who were 21-70 years of age classified as ASA I and II with BMI ≤40 undergoing abdominal procedures with duration ≤ 180 minutes were submitted to this study.
The patients were divided randomly into three equal groups. They all received an activation epidural dose, 20 minutes before the end of the procedure according to the study groups by injection of a mixture of bupivacaine 0.125% plus dexmedetomidine or fentanyl or normal saline 1.5 mL/segment depending on the number of segments to be blocked.
The three groups were:
Dexmedetomidine group
Dexmedetomidine 1 ml (100 μg) plus 1 ml normal saline was mixed with 48 ml bupivacaine 0.125% in an elastomeric pump. The rate of epidural infusion was 5ml/hr for the postoperative 24 hours.
Fentanyl group
Fentanyl 2 ml (100 μg) was mixed with 48 ml bupivacaine 0.125% in an elastomeric pump. The rate of epidural infusion was 5ml/hr for the postoperative 24 hours.
Control group
Normal saline 2 ml was mixed with 48 ml bupivacaine 0.125% in an elastomeric pump. The rate of epidural infusion was 5ml/hr for the postoperative 24 hours.
After complete recovery from general anesthesia, epidural infusion was started according to the study groups. The infusion continued for the first 24 hours postoperative period. Patients with breakthrough pain received additional analgesia with paracetamol and pethidine when needed.
The following parameters were monitored during the study period (24 hours after the end of surgery): onset of sensory analgesia, duration of analgesia, postoperative pain score using the Visual Analogue Scale (VAS), additional requirements for supplementary analgesia, hemodynamic parameters including Mean arterial blood pressure (MAP), Heart rate (HR) and Peripheral oxygen saturation in blood (SpO2) and the occurrence of any adverse events like respiratory depression, nausea, vomiting, pruritus, shivering, headache etc. were carefully observed, recorded and managed symptomatically during the study period.
The present study revealed that addition of dexmedetomidine as analgesic adjuvant to epidural bupivacaine after abdominal surgeries produce preferable analgesia (less VAS values) with reduced analgesic needs and consumption compared to fentanyl. Side effects like nausea, vomiting, pruritis, urine retention, and respiratory depression were less with the use of epidural dexmedetomidine than with epidural fentanyl. However, compared to epidural fentanyl, epidural dexmedetomidine is more frequently associated motor block, bradycardia, hypotension and dry mouth.