Intrathecal Dexmedetomidine versus Fentanyl as Adjuvants to Hyperbaric Bupivacaine for Spinal Anaesthesia in Elective Gynaecological Procedures: A Double-blinded Randomised Clinical Trial

Abstract

Introduction: Spinal anaesthesia is commonly used for elective gynaecological surgery. Hyperbaric bupivacaine provides dependable neuraxial blockade, but postoperative analgesic duration may be inadequate. Intrathecal dexmedetomidine and fentanyl improve block quality and prolong analgesia, although their adverse-effect profiles differ. Aim: To compare intrathecal dexmedetomidine 5 µg with intrathecal fentanyl 25 µg as adjuvants to 0.5% hyperbaric bupivacaine for spinal block characteristics in women undergoing elective gynaecological procedures. Materials and Methods: The present double-blinded randomised parallel-group clinical trial was conducted in the Department of Anaesthesiology, Krishna Institute of Medical Sciences, Krishna Vishwa Vidyapeeth (Deemed to be University), Karad, Maharashtra, India, from June 2024 to November 2025. The study enrolled 60 women aged 18-60 years with American Society of Anaesthesiologists (ASA) physical status I or II. Eligible participants were randomly distributed into two equal groups. In Group DEX, patients received intrathecal 0.5% hyperbaric bupivacaine 15 mg with dexmedetomidine 5 µg. In Group FEN, patients received intrathecal 0.5% hyperbaric bupivacaine 15 mg with fentanyl 25 µg. Sensory and motor block characteristics, postoperative analgesic profile, haemodynamic changes, and adverse effects were assessed at predefined intervals. Statistical analysis was performed using the independent samples t-test, Mann-Whitney U test, Chi-square test, or Fisher’s-exact test, depending on the type and distribution of data. Statistical significance was set at p<0.05. Results: The mean age was 42.3±9.1 years in Group DEX and 41.7±8.6 years in Group FEN; ASA physical status I/II distribution was 18/12 and 17/13, respectively, with comparable baseline characteristics. Dexmedetomidine produced faster sensory block onset than fentanyl (2.4±0.6 versus 3.8±0.9 minutes; p<0.001) and significantly prolonged sensory and motor blockade. Time to first rescue analgesia was significantly longer with dexmedetomidine (382.7±41.2 versus 261.5±36.8 minutes; p<0.001), with fewer rescue analgesic doses and lower early postoperative pain scores. Haemodynamic effects were clinically manageable in both groups; bradycardia was more frequent with dexmedetomidine, whereas pruritus occurred only with fentanyl. Conclusion: Intrathecal dexmedetomidine 5 µg, when added to hyperbaric bupivacaine, provided quicker establishment of spinal anaesthesia and longer postoperative analgesia than intrathecal fentanyl 25 µg in elective gynaecological surgery. Careful monitoring for bradycardia is required when dexmedetomidine is used.