Comparison of Dexmedetomidine and Fentanyl as Adjuvants to Bupivacaine in Spinal Anesthesia: A Randomized Controlled Study

Abstract

Background: Spinal anesthesia is widely used for lower abdominal and lower limb surgeries due to its rapid onset, reliable blockade, and minimal systemic effects. The addition of adjuvants to local anesthetics can enhance sensory and motor blockade, prolong postoperative analgesia, and reduce the need for systemic opioids. This study compares dexmedetomidine and fentanyl as adjuvants to hyperbaric bupivacaine in spinal anesthesia, evaluating their effects on block duration, hemodynamic stability, and postoperative analgesia.

Methods: This prospective, randomized controlled trial was conducted on 90 patients (ASA I–II) undergoing elective lower limb and infraumbilical surgeries under spinal anesthesia. Patients were divided into three groups: Group B (control, n = 30) received bupivacaine alone (15 mg, 0.5%), Group D (n = 30) received bupivacaine with dexmedetomidine (5 µg), and Group F (n = 30) received bupivacaine with fentanyl (25 µg). Parameters including onset and duration of sensory and motor block, hemodynamic stability, sedation levels, and postoperative analgesia duration were recorded. Statistical analysis was performed using SPSS v.24, with a p-value < 0.05 considered significant.

Results: The onset of sensory and motor block was faster in Group D (dexmedetomidine) compared to Group F (p < 0.001). The duration of sensory blockade was longest in the dexmedetomidine group (p < 0.001), followed by the fentanyl group. Hemodynamic stability was comparable among all groups, though hypotension was more common in Group D (p = 0.028). Postoperative analgesia lasted significantly longer with dexmedetomidine (p < 0.001), reducing the need for rescue analgesia. Sedation scores were higher in Group D, but no cases of respiratory depression were observed.

Conclusion: Dexmedetomidine as an adjuvant to bupivacaine in spinal anesthesia provides prolonged sensory and motor blockade, better postoperative analgesia, and mild sedation, making it superior to fentanyl. However, it is associated with a higher incidence of hypotension. Fentanyl offers good intraoperative stability and moderate analgesia but has a shorter duration of action. The choice between these adjuvants should be based on surgical duration, patient hemodynamics, and analgesia requirements.

Keywords: Spinal anesthesia, Bupivacaine, Dexmedetomidine, Fentanyl, Postoperative analgesia