الفهرس 
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Abstract
S
hivering is one of the common troublesome complications involving regional anesthesia which causes discomfort in parturient undergoing cesarean sections. Shivering can impair pulse oximetry and electrocardiogram monitoring. It can also increase demand for oxygen and production of carbon dioxide and may also have a role in the intensification of wound pain, reduced wound healing and delayed discharge from recovery unit.
Spinal anaesthesia impairs the thermoregulatory system through inhibiting tonic vasoconstriction, which plays an important role in temperature regulation. In addition, spinal anaesthesia causes redistribution of core heat from the trunk (below the block level) to the peripheral tissues. These two effects make patients vulnerable to hypothermia and consequently shivering.
Dexmedetomidine is a highly selective α2-adrenoreceptor agonist that binds to a transmembrane G protein-binding receptor. Pre-clinic evidence showed that dexmedetomidine, used as a local anesthetic adjuvant for intravertebral anaesthesia can shorten the onset time of the block, decrease postoperative pain intensity, prolong the duration of the block and reduce the requirement of analgesics. Most importantly, it can increase vasodilatation and the thresholds for shivering and inhibit central thermoregulation.
Fentanyl is an μ receptor agonist and it has been used intrathecally for many years and recently also given in combination with bupivacaine to improve the quality and the quantity of spinal anaesthesia and prolong the duration of postoperative analgesia. Fentanyl has been found to affect the spinal afferent thermal inputs and thermo regulator at the spinal cord. Therefore, we hypothesized that fentanyl added to intrathecal hyperbaric bupivacaine could effectively prevent shivering associated with spinal anaesthesia.
The purpose of this work is to compare the efficacy of fentanyl and dexmedetomidine in prevention of perioperative shivering when added to hyperbaric bupivacaine intrathecally in cesarean sections and their effect on the intraoperative hemodynamics, intensity of the block, sedation, postoperative pain and analgesic requirement.
Study included 150 obstetric patients who fulfilled all the points in the inclusion and randomized into 3 equal group: control group, fentanyl group and dexmedetomidine group. Each group consisting of 50 patients, namely:
Control group: received 0.5ml normal saline 0.9% with 12. 5 mg hyperbaric bupivacaine 0. 5% intrathecally.
Fentanyl group: received 10µg fentanyl with 12. 5 mg hyperbaric bupivacaine 0. 5% intrathecally.
Dexmedetomidine group: received 10μg dexmedetomidine with 12. 5 mg hyperbaric bupivacaine 0. 5% intrathecally.
The comparison included assessment of intra and postoperative hemodynamics, sensory and motor block, incidence of shivering and sedation and assessment of adverse events.
This study showed that there is no statistical difference between both fentanyl and dexmedetomidine groups regarding the incidence and intensity of shivering but there was statistical difference between them and the control group.
Regarding the time of sensory and motor block, it was of faster onset and prolonged duration in both fentanyl and dexmedetomidine groups compared to the control group but dexmedetomidine group was of faster and longer duration compared to other groups. Therefore, time to first analgesic rescue was longest in dexmedetomidine group.
Regarding the hemodynamic parameters dexmedetomidine group showed statistically significant difference regarding hypotension but non statistically significant difference regarding bradycardia compared to other groups.
For sedation intensity, there were no statistical difference between the groups. Regarding other reported adverse effects, there was a higher incidence of nausea, vomiting as well as pruritis with a significant statistical difference between fentanyl and other study groups.