ASSESSMENT OF PREMIXED VERSUS SEQUENTIAL ADMINISTRATION OF HYPERBARIC LEVOBUPIVACAINE WITH FENTANYL FOR SENSORY EFFECT OF SPINAL ANAESTHESIA IN PATIENTS UNDERGOING LOWER ABDOMINAL SURGERIES

Background: Spinal anaesthesia is widely employed for elective lower abdominal surgeries because of its rapid onset, reliable sensory blockade, excellent muscle relaxation, and favourable recovery profile. Hyperbaric levobupivacaine is increasingly preferred due to its reduced cardiotoxicity and improved safety profile compared with racemic bupivacaine. Intrathecal fentanyl is commonly used as an adjuvant to enhance block quality and postoperative analgesia. However, limited evidence exists regarding whether sequential administration of hyperbaric levobupivacaine and fentanyl offers advantages over premixed administration in terms of sensory block characteristics, haemodynamic stability, and postoperative analgesia. Methods: This prospective observational comparative study was conducted in the Department of Anaesthesiology, Sree Balaji Medical College and Hospital, Chennai, between October 2024 and October 2025. A total of 58 patients aged 18 60 years belonging to ASA physical status I and II and undergoing elective lower abdominal surgeries under spinal anaesthesia were enrolled. Participants were allocated into two groups of 29 patients each. Group S received sequential intrathecal administration of hyperbaric levobupivacaine followed by fentanyl, whereas Group M received a premixed intrathecal solution of the same drugs. Sensory block characteristics, haemodynamic parameters, and postoperative analgesic outcomes were assessed and compared between the groups. Results: Baseline demographic and clinical characteristics were comparable between groups. The onset of sensory block was significantly faster in Group S than in Group M (3.72 ± 0.81 vs. 4.45 ± 0.90 minutes; p=0.003). The duration of sensory blockade was significantly prolonged in Group S, with regression to the L1 dermatome occurring at 103.28 ± 11.98 minutes compared with 91.86 ± 10.95 minutes in Group M (p<0.001). Mean arterial pressure was significantly higher in Group S (83.52 ± 6.21 mmHg) than in Group M (79.90 ± 6.84 mmHg; p=0.031). The incidence of hypotension (17.24% vs. 37.93%) and vasopressor requirement (13.79% vs. 34.48%) were lower in Group S. Postoperative analgesia was significantly superior in Group S, with a longer time to first rescue analgesia (198.52 ± 26.21 vs. 162.48 ± 23.95 minutes; p<0.001) and lower total analgesic consumption (108.97 ± 27.84 vs. 146.21 ± 32.59 mg; p<0.001). Conclusion: Sequential intrathecal administration of hyperbaric levobupivacaine and fentanyl provides faster onset and longer duration of sensory blockade, improved haemodynamic stability, prolonged postoperative analgesia, and reduced analgesic consumption compared with premixed administration. Sequential administration may therefore represent a simple and effective strategy for optimizing spinal anaesthesia in elective lower abdominal surgeries.