Intrathecal Magnesium Sulfate and Meperidine on Sensory and Motor Block During Spinal Anesthesia: A Randomized Clinical Trial in Iran

Background: Spinal anesthesia in orthopedic surgeries presents challenges, especially concerning the choice of anesthetic agents and their adjuncts, which affect analgesia quality and potential side effects. This study was conducted with the aim of determining the effects of intrathecal bupivacaine, meperidine and magnesium sulfate on hemodynamic parameters, onset and duration of sensory/motor block in spinal anesthesia in patients with lower limb fractures. Methods: This double-blind, randomized clinical trial included 130 patients who were candidates for planned lower limb orthopaedic surgery. They were divided into four groups: 1: bupivacaine 10 mg, 2: meperidine (1 mg/kg), 3: bupivacaine 10 mg + magnesium sulfate of 100 mg, and 4: meperidine (1 mg/kg) + magnesium sulfate with (100 mg). Parameters measured included hemodynamic status and sensory and motor block onset and duration. The level of sensory block was assessed via the pinprick sensation method, while the Bromage scale was used to evaluate motor block. Results: No clinically significant differences in hemodynamic parameters were observed across the groups. The onset of sensory block (P value= 0.235), onset of motor block (P value= 0.097), and duration of motor block (P value= 0.135) were statistically similar across the groups. However, significant differences were found in the duration of the sensory block (P value= 0.035). Magnesium sulfate increased the duration of motor block in the meperidine group (80.93 ± 30.28 minutes). However, it reduced the duration in the bupivacaine group (75.23 ± 38.56 minutes) Motor block onset was prolonged in groups receiving magnesium sulfate, with a significant difference between the meperidine and meperidine with magnesium sulfate groups (CI = 1.10 to 12.52, P value = 0.04). Conclusion: The intrathecal drugs used did not produce significant side effects, suggesting that they can be used interchangeably... However, magnesium sulfate, as an adjuvant, did not enhance the length or quality of the block in spinal anesthesia when used with meperidine and bupivacaine