Effectiveness of 0.5% Ropivacaine with Magnesium Sulfate versus 0.5% Ropivacaine Alone in Ultrasound-guided Supraclavicular Brachial Plexus Block: A Prospective Observational Study
TL;DR
Adding magnesium sulfate to 0.5% ropivacaine with magnesium sulfate did not significantly prolong the duration of postoperative analgesia, however, it was associated with reduced postoperative tramadol requirements and increased early sedation, while maintaining haemodynamic stability.
Abstract
Introduction: In regional anaesthesia, a rapid onset of analgesia was clinically important because it improved patient comfort and may reduce the need for rescue analgesics. Evaluating the efficacy of a drug as an adjuvant can help identify approaches to achieve faster, more effective postoperative pain control. Aim: To assess the efficacy of 0.5% ropivacaine with magnesium sulfate versus 0.5% ropivacaine alone in ultrasound-guided supraclavicular brachial plexus block. Materials and Methods: This prospective observational study was conducted in the main Operation Theatre (OT) of the Department of Anaesthesia, Kottayam Government Medical College, Kottayam, Kerala, India, from July 2023 to July 2024. The study included American Society of Anaesthesiologists (ASA) physical status I and II patients aged 18-65 years posted for upper limb surgeries under ultrasound-guided supraclavicular block. Patients having peripheral neuropathy, bleeding disorders, and allergies to local anaesthetics or magnesium sulfate were excluded. Consecutive sampling resulted in 52 patients receiving 0.5% ropivacaine with 150 mg magnesium sulfate (Group A) and another 52 receiving 0.5% ropivacaine alone (Group B). The primary outcome was the duration of postoperative analgesia. Secondary outcomes were the onset of sensory and motor block, postoperative pain using the Visual Analogue Scale (VAS), sedation (Ramsay) scores, rescue-analgesic requirements, and haemodynamic parameters. Demographic data were also recorded. Non normally distributed/ordinal outcomes were compared by Mann-Whitney U, categorical rescue analgesia by Fisher’s-exact test, and haemodynamics by repeated-measures Greenhouse-Geisser; effect sizes and per-family Bonferroni correction reported throughout. Results: A total of 104 patients (52 per group) were included. Baseline demographic characteristics were comparable between groups. The median duration of postoperative analgesia was similar in the magnesium and control groups {468.5 (IQR 155) vs 470.0 (IQR 129) min; p=0.610}. The magnesium group had a faster onset of sensory block {15.0 (IQR 10) vs 18.5 (IQR 5) min; p=0.042} and motor block {15.0 (IQR 10) vs 18.0 (IQR 5) min; p=0.042} and this difference remained significant after Bonferroni correction (VAS at postoperative 6 h was significantly lower in Group A than in Group B [p=0.007], α=0.0083). Paracetamol consumption was comparable between groups, whereas fewer patients in the magnesium group required tramadol rescue analgesia (42.3% vs 75.0%; adjusted OR 3.92, 95% CI 1.66– 9.25; p=0.002). Early postoperative sedation was higher in the magnesium group {0 h: 4.0 (IQR 0) vs 3.0 (IQR 1); p<0.001}, with no clinically significant haemodynamic differences. Conclusion: Adding magnesium sulfate to 0.5% ropivacaine did not significantly prolong the duration of postoperative analgesia. However, it was associated with reduced postoperative tramadol requirements and increased early sedation, while maintaining haemodynamic stability.