Effects of Adding Two Different Doses of Intrathecal Magnesium Sulfate to Bupivacaine in Laminectomy Surgeries under Spinal Anesthesia

Spinal anesthesia is a popular anesthetic technique in laminectomy due to less complication and more satisfaction of patients and surgeons. In this technique, duration and quality of block is important to control postoperative pain. The aim of this study was to evaluate the effect of adding two different doses of magnesium sulfate to bupivacaine on block characteristics and postoperative pain in laminectomy under spinal anesthesia.
In a prospective clinical trial study, 120 candidates of elective laminectomy under spinal anesthesia with bupivacaine were randomly divided to three groups of receiving 50 mg magnesium sulfate (M50), 100 mg magnesium sulfate (M100) and normal saline (N). The onset and duration of sensory and motor block, maximum level of block, time of analgesic requirement and its dose were measured and recorded.
Findings: The mean onset time of sensory block in M50 (16.9 ± 4.0 minutes) and M100 (18.5 ± 2.4 minutes) were significantly more than control group (12.6 ± 3.57 minutes). The duration of sensory block was 89.80 ± 12.79, 116.50 ± 12.00, and 119.00 ± 18.50 minutes in control, M50, and M100 groups, respectively, with significant difference. Mean onset time of motor block in both M50 (11.80 ± 4.20 minutes) and M100 (12.6 ± 3.80 minutes) groups and were significantly more than control group (9.40 ± 3.33 minutes). The pain intensity was significantly more in control group. The mean time of first analgesic requirement and its total dose were significantly lower in M100 than other groups (P 0.050 for all)
Adding 100 mg intrathecal magnesium sulfate in comparison with 50 mg provides more acceptation effects such as less sensation of pain, less analgesic consumption and prolonged first time of analgesic requirement with no significant side effect.