The effect of adding magnesium sulphate as an adjuvant to peribulbar block for glaucoma surgery in morbidly obese patients: A randomized controlled study

Abstract

Background This study aimed to evaluate safety and efficacy of magnesium sulphate as an adjuvant to peribulbar block at two different doses (75 and 100 mg) in reducing intraocular pressure (IOP) in obese patients undergoing glaucoma surgery. Methods Forty-six adult patients, American Society of Anesthesiologists status I–III, with body mass index of 30–55 kg/m2 undergoing glaucoma surgery under peribulbar block were enrolled during February, 2021. Patients were randomly assigned into two groups (1:1). Both groups received 4 ml of lidocaine 2%, 4 ml of bupivacaine 0.5%, and 1 ml of hyaluronidase (10IU of hyaluronidase/ml of lidocaine). Magnesium sulphate was added to this mixture either in a dose of 75 mg (group I) or 100 mg (group II). Primary outcomes included onset of globe and lid akinesia and IOP. Secondary outcomes included durations of analgesia and motor block, patients’ and surgeons’ satisfaction, and vital data. Results The mean onsets to globe and lid akinesia were significantly lower in group II compared to group I (2.7 vs. 4.2 min, p < 0.001 and 3.1 vs. 4.2 min, p = 0.001, respectively). After the block, the mean IOP was significantly lower in group II at 1 min (27.2 vs. 32.7 mmHg, p = 0.0034), 3 min (26.5 vs. 32.4 mmHg, p = 0.002) and 5 min (26.2 vs. 32.1 mmHg, p = 0.001). Group II had a significantly longer mean durations of analgesia (3.5 vs. 2 hours, p < 0.001) and recovery of motor block than group I (3.3 vs. 2.3 hours, p < 0.001). No complications were encountered during the surgery. Conclusion Magnesium sulphate at a dose of 100 mg demonstrated higher efficacy while maintaining safety compared to the dose of 75 mg.

Keywords

• adjuvant
• akinesia
• analgesia
• glaucoma
• magnesium sulphate
• peribulbar block