Effects of Intrathecal Bupivacaine with Adjuvants Midazolam versus Magnesium Sulphate in Tibia Fibula Surgeries: A Randomised Clinical Study
Authors: Sharma Tejash H , Jain Jagrati , Shah Aanal , Chavda Dushyant , Chauhan Dinesh K 
Published: January 2025

Introduction: Intrathecal adjuvants like magnesium sulphate, midazolam and opioids are increasingly used with local anaesthetic for spinal anaesthesia to intensify subarachnoid block and improve haemodynamic stability. Midazolam, a benzodiazepine, is mainly used for anxiolysis, amnesia and sedation. It also exhibits a muscle relaxant effect via its action on the glycine receptors in the spinal cord. Magnesium sulphate is a pharmacological agent used in a variety of clinical conditions. It potentiates opioid nociception and prolongs the duration of anaesthesia. The analgesic properties of magnesium sulphate are primarily related to regulating calcium influx into cells and antagonism of N-methyl D-aspartate (NMDA) receptors.

Aim: To observe the efficacy of intrathecal 2.5 mg midazolam and 50 mg magnesium sulphate as adjuvants to 0.5% hyperbaric bupivacaine in tibia-fibula surgeries and haemodynamic stability in both groups.

Materials and Methods: The present double-blind, prospective randomised clinical study was conducted in the Department of Anaesthesiology, Dhiraj Hospital, Sumandeep Vidyapeeth, Piparia, Vadodara, Gujarat, India, from February 2021 to December 2022. Study included 64 patients of either gender, classified as American Society of Anaesthesiologists (ASA) grade I/II, undergoing tibia-fibula surgeries. Patients were divided into two groups: Group BM (Midazolam) received 0.5% hyperbaric bupivacaine 3.2 mL+2.5 mg midazolam (0.5 mL), totaling 3.7 mL and group BMS (Magnesium sulphate) received 0.5% hyperbaric bupivacaine 3.2 mL+50 mg magnesium sulphate (0.5 mL), totaling 3.7 mL. The primary objective was to observe Heart Rate (HR), Blood Pressure (BP), Oxygen Saturation (SpO2 ) and Respiratory Rate (RR). Secondary objectives were to observe the time to onset of sensory and motor blockade, duration of sensory and motor blockade, time of two-segment regression, duration of analgesia, sedative effect (intra and postoperative), and any side effects or complications. Statistical analysis was performed using International Business Machines (IBM) Statisical Package for the Social Sciences (SPSS) statistics for Windows software.

Results: The mean Standard Deviation (SD) age in group BM was 37.63±11.50 years and in group BMS was 40.81±11.93 years. The onset and duration of sensory and motor blockade were better in group BM than in group BMS (p-value <0.05). In terms of complications, bradycardia was noted in a few cases in group BM after giving spinal anaesthesia. In group BM at two minutes, the mean HR was 76.12±10.71 beats per minute, which was significantly lower than in group BMS 87.56±7.76 beats per minute (p-value <0.05). Hypotension was noted after spinal anaesthesia in group BM. At two minutes, Systolic Blood Pressure (SBP) was 94.81±19.69 mmHg in group BM and 123.0±8.34 mmHg in group BMS (p-value <0.05); at 10 minutes, SBP was 106.0±14.91 mmHg in group BM and 117.3±12.20 mmHg in group BMS (p-value <0.05).

Conclusion: Intrathecal magnesium sulphate (50 mg) provided better haemodynamic stability compared to intrathecal midazolam (2.5 mg) in patients undergoing tibia-fibula surgeries.