Comparative analgesic efficacy of intravenous vs intrathecal dexmedetomidine as an adjuvant to hyperbaric bupivacaine in subarachnoid block for below knee orthopaedic surgery

BACKGROUND AND AIM: Intrathecal and intravenous dexmedetomidine has been used as adjuvant in subarachnoid block [SAB]. The aim of this study was to compare the analgesic efficacy of intravenous vs intrathecal dexmedetomidine as adjuvant to intrathecal bupivacaine. METHODS: Ninety patients, aged 20–60 years belonging to American Society of Anaesthesiologists (ASA) physical status I and II, scheduled for below knee orthopaedic surgeries under SAB were enrolled. In group I (n = 45) patients received intravenous dexmedetomidine 0.5 μg/kg in 100 mL 0.9% normal saline [NS] intravenous over a period of 15 minutes given 20 minutes before SAB. Subarachnoid block was given with intrathecal (IT) 0.5% bupivacaine (H) 12.5 mg (2.5 mL) with 0.3 mL of NS. Patients in group II (n = 45) received 100 mL of 0.9% NS over a period of 15 minutes given 20 minutes before subarachnoid block. SAB was given with intrathecal 0.5% heavy bupivacaine 12.5 mg with 3 μg of dexmedetomidine (0.3 mL). The primary outcome was duration of analgesia and rescue analgesic requirement, whereas secondary outcome included pain scores. RESULTS: The duration of analgesia was prolonged in group II (median [IQR]: 5 (6–7.5) h than in group I (median[IQR]: 4[2–4.5] h, P = 0.000). Median dose of rescue analgesics over period of 24 hours was less in group II as compared to group I (median [IQR]:150 (75–150) mg vs 195 (150–225) mg, P = 0.000). VAS score was lower in group II till 12 h in the postoperative period (P = 0.00). CONCLUSION: Intrathecal dexmedetomidine is more efficacious as compared to intravenous dexmedetomidine, due to favourable outcomes in terms of increased duration of postoperative analgesia and reduced rescue analgesic requirement.