Comparative study of intrathecal dexmedetomidine, fentanyl, and magnesium sulfate as adjuvants to 0.5% hyperbaric bupivacaine for knee arthroscopic surgeries

Background and aim Fentanyl is one of the short-acting narcotic analgesics with potent morphine-like action. Dexmedetomidine is a highly selective α2 adrenergic agonist which has been used for premedication and as an adjunct to general anesthesia. Mg is a noncompetitive antagonist to NMDA receptors and has the potential to prevent central sensitization from peripheral nociceptive stimulation. We aimed to assess the onset and duration of analgesia, sensory and motor blockade, hemodynamic effects, and postoperative analgesic requirement. Patients and methods This study was carried out on 60 patients scheduled for knee arthroscopic surgeries. Patients were assigned into four groups: group I received 15 mg of 0.5% hyperbaric bupivacaine intrathecally+0.5 ml of normal saline. Group II received 15 mg of 0.5% hyperbaric bupivacaine+50 mg MgSO 4 . Group III received 15 mg of 0.5% hyperbaric bupivacaine+25 μg of fentanyl. Group IV received 15 mg of 0.5% hyperbaric bupivacaine+5 μg of diluted dexmedetomidine. Results The intraoperative heart rate and mean arterial pressure was significantly lower in (group II, group III, and group IV) than in group I. The onset of sensory block was significantly lower in group IV than in group I, group II, and group III and significantly lower in group II and group III than in group I. Duration of analgesia was significantly delayed in group IV than in group I, group II, and group III. Conclusion Intrathecal dexmedetomidine provides a superior effect as it is associated with stable hemodynamics, lower onset of sensory block, and opioid consumption compared to MgSO 4 , fentanyl, and normal saline group.