Effect of Intrathecal Magnesium Sulfate as an Adjuvant to Spinal Anesthesia: A Prospective Study

Spinal anesthesia is a common procedure, but its short duration and limited postoperative analgesia remain challenges. Magnesium sulfate, through N-methyl-D-aspartate receptor antagonism and calcium channel regulation, has become a promising adjuvant in regional anesthesia. Objectives: To evaluate the effect of magnesium sulfate addition to local anesthetic agents in the process of spinal anesthesia, including its safety profile and the optimal dose, and to measure its postoperative analgesic results. Methods: This prospective follow-up study included 150 adult patients with ASA I- II, undergoing lower abdominal or limb surgery under spinal anesthesia with intrathecal magnesium sulfate. Sensory and motor block characteristics, hemodynamic variables, postoperative pain (VAS), the first analgesic order, total analgesics, and side effects were assessed over 7 days via Repeated-Measures ANOVA in SPSS. Results: In the follow-up period, magnesium sulfate increased the time of motor and sensory block significantly (motor: 130 ± 20min -170 ± 28min, p<0.001; sensory: 165 ± 22 min at 1 h -215 ± 30min at Day 7, p<0.001). An increased delay to first analgesic request (270 ± 38 minutes), a decreasing VAS pain response (3.0 ± 0.5 → 2.2 ± 0.5, p<0.001), and a reduction in per-period analgesic consumption (220 ± 25 mg to 150 ± 18 mg) all revealed better postoperative analgesia. The adverse effects were mild, and the hemodynamic parameters remained stable. Conclusion: Magnesium sulfate safely prolongs block duration and analgesia after surgery, without affecting hemodynamic stability.