Intrathecal Dexmedetomidine and Fentanyl as Adjuvant to Bupivacaine on Duration of Spinal Block in Addicted Patients

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.