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Background: Addicted patients have innate tolerance to local anesthetics in both neuraxial and peripheral blocks. Dexmedetomidine (Dex) is a highly selective α2 adrenergic receptor agonist used as additive to increase quality and duration of peripheral nerve blocks. Objectives: The current study aimed to compare the effect of dexmedetomidine and fentanyl additives on bupivacaine to prolong the duration of block and minimizing side effects. Patients and Methods: Patients were candidates for elective surgery less than three hours of lower abdomen or lower extremities surgeries. Patients were randomly allocated to receive dexmedetomidine 5 µg added to 12.5 mg (2.5 mL) of 0.5% hyperbaric bupivacaine (DEX group), or 25 µg (0.5 mL) fentanyl added to 12.5 mg (2.5 mL) of 0.5% hyperbaric bupivacaine (F group) or only 12.5 mg of 0.5% hyperbaric bupivacaine. Data were recorded based on sensory block. Motor block was tested using modified Bromage scale every 30 minutes until the end of block. Time to return of sensory block to 4 dermatomes below and time to return of Bromage scale to 0 were recorded. All vital measurements (oxygen saturation, heart rate, electrocardiogram, and non-invasive blood pressure) were performed at 0, 30, 60, 90, 120 and 180 minutes in all three groups of the study. Group DEX received dexmedetomidine additive and group F received fentanyl additive and group C (control) received normal saline. Results: Totally, 84 patients were randomly divided into three groups of 28 patients. Onset of sensory block in DEX group was significantly lower than those of fentanyl (P = 0.012) and control groups (P = 0.001). Duration of sensory block was significantly longer in DEX group compared to Fentanyl (P = 0.043) and control (P = 0.016) groups. Duration of motor block in the DEX group was significantly longer than those of the fentanyl (P = 0.014) and control groups. Heart rate and mean arterial pressure were significantly higher in the DEX group at 30, 60, 90,120, and 180 minutes compared to those of the other two groups (P < 0.05). Conclusions: Dexmedetomidine added to bupivacaine in spinal anesthesia is more effective to increase duration of block, providing more appropriate sedation and less postoperative pain scale and post-operative nausea and vomiting (PONV) compared to fentanyl additive.

Background: Postoperative pain is one of the most common problems after hernia repair. Decrease in postoperative pain accelerates functional recovery, decreases duration of hospital stay and postoperative morbidity. Objectives: To compare postoperative analgesic effect of infiltration of magnesium versus bupivacaine into incision of inguinal hernia repair. Patients and Methods: In a double blind clinical trial, 80 patients’ candidates for elective inguinal hernia repair were enrolled. Right before closure of incision, in Bupivacaine group 5 mL Bupivacaine 0.5% added to 5 mL normal saline and in Magnesium group, 10 mL Magnesium sulfate 20% was infused subcutaneously. Pain score was measured using numeric rating score (NRS) at 1, 3, 6, 12 and 24 hours postoperatively. If NRS was above 3, 1 mg morphine was administered as rescue analgesic until patient felt comfortable or NRS < 3. Results: Postoperative pain scores at 1 and 3 hours were not significantly different between bupivacaine and magnesium groups (P = 0.21, 0.224; respectively). However, at 6 (P = 0.003), 12 (P = 0.028) and 24 (P = 0.022) hours postoperative, pain score (NRS) was significantly lower in bupivacaine group. Number of patients needed at least 1 dose of rescue morphine (P = 0.001), mean number of episodes asked for morphine during next 24 hours (P = 0.001) and total dose of morphine requirement (P = 0.01) were significantly lower in bupivacaine group. Conclusions: Magnesium infiltration did not decrease total dose and number of episodes needed for morphine rescue analgesic. Bupivacaine infiltration into surgical site was more effective than magnesium sulfate infiltration in postoperative pain control.