Effect of adding magnesium to bupivacaine and fentanyl for spinal anesthesia in lower limb orthopaedic surgeries

In recent years spinal anesthesia using a local anesthetic in combination with an opioid has gained popularity for lower limb operations due to the high success rate and patient satisfaction، and the decreased resource utilization compared with general anesthesia. In experimental studies، intrathecal administration of magnesium sulphate (MgSO4) significantly potentiated antinociception during spinal anesthesia; however available data are scarce. This study aimed at evaluating the effect of adding MgSO4 to bupivacaine and fentanyl for spinal anesthesia in lower limb orthopaedic surgeries. Methods & materials: In this double-blind randomized clinical trial، 100 candidates of spinal anesthesia for lower limp orthopaedic surgeries (ASA class I-II) were recruited in Hazrat Rasoul Akram Medical Complrx in a 10-month period. They randomized in two equal age- and sex-matched groups receiving 1. 0 ml of preservative-free 0. 9% sodium chloride (group S) or 50 mg of MgSO4 5% (1. 0 ml) (group M) following 12. 5 mg of bupivacaine 0. 5% plus 25 μg of fentanyl intrathecally. Date were collected regarding the time to reach the highest level of sensory blockade، time to L2 regression، times to reach the highest level of motor blockade and its full regression، time to consumption the first dose of postoperative analgesic and complications. Median time to reach the highest level of sensory blockade was significantly higher in the S group (16 vs. 14. 5 min; p=0. 02). Median time to L2 regression (243 vs. 207 min; p<0. 001)، as well as the median time to consumption the first dose of postoperative analgesic (345 vs. 232 min; p<0. 001) were significantly higher in the M group. Median times to reach the highest level of motor blockade and its full regression were comparable between the two groups. Hypotension and bradycardia were recorded in 20% and 10% of the patients in group M and 30% and 14% of patients n group S، respectively (p=0. 35). Intrathecal MgSO4 along with the spinal anesthesia with bupivacaine and fentanyl in lower limb orthopaedic surgeries hasten the sensory blockade and prolongs the period of anesthesia without additional side effects or influence on the motor blockade.