Abstract Background: Spinal anaesthesia is used widely and safely over 100 years especially for operations involving the lower abdomen and perineum. Although hyperbaric Bupivacaine 0.5% is extensively used intrathecally, it does not produce prolonged postoperative analgesia. Hence, opioids like morphine and fentanyl which have synergistic effects are used for prolonged postoperative analgesia. Non-opioid adjuvant drugs like Magnesium sulphate are becoming increasingly popular approaches for perioperative pain management. Aims and Objectives: The present study was carried out to know the effects of adding intrathecal magnesium sulphate to Bupivacaine and Fentanyl on the onset of sensory and motor blockade as well as its maximum level and the time taken to achieve it and the total duration of analgesia. Methods: A prospective randomized control study involving 80 adult patients of ASA 1 and 2, satisfying inclusion and exclusion criteria scheduled for elective infra umbilical oncosurgeries was carried out after obtaining institutional ethical Committee approval at Kidwai Memorial Institute of Oncology, Bangalore. Forty patients of Group A received  Inj. Magnesium Sulphate 50 mg (0.1ml) +inj 0.5% bupivacaine heavy15mg (3ml)+Inj Fentanyl 20 mcg (0.4ml) intrathecally. 40 patients of Group B received 0.1ml of Normal saline + inj 0.5% bupivacaine Heavy 15mg (3ml)+Inj Fentanyl 20 mcg (0.4ml) intrathecally. Then Sensory and motor blockade assessed, hemodynamic parameters were recorded. Statistical analysis was performed by descriptive statistics to calculate the mean and standard deviation, the t-test, χ ² tests for calculating the materiality for establishing the results.  Results: the mean onset time (mins) of both sensory and motor blockade as well as the time to attain highest dermatomal levels were more in Group A compared to Group B and was statistically significant. (p<0.001). There was significant difference in the maximum level of sensory block attained between the two groups with Group A attaining mean level of T₇-T₆ and Group B attaining mean level of T₈-T₇ with p value 0.025. The mean duration (mins) of effective analgesia was found to be higher in Group A compared to Group B and the difference between them was statistically significant   (p 0.011). Conclusion: Though the addition of Magnesium sulphate to Bupivacaine and fentanyl intrathecally delays the onset of sensory and motor blockade, it achieves a higher dermatomal blockade and prolongs the duration of blockade hence is a promising non-opioid adjuvant for prolonged analgesia.

Keywords: Magnesium Sulphate,Non-opioid Intrathecal Adjuvants.