Intrathecal Magnesium Sulfate as Analgesic and Anaesthetic Adjunct to Bupivacaine in Patients Undergoing Lower Extremity Orthopaedic Surgery

Abstract

Background

Subarachnoid block is a popular mode of anesthesia for lower limb surgeries. Studies of Magnesium Sulfate (MgS0₄ ) as an adjuvant to intrathecal local anaesthetic  are limited. The objective  was to find out the analgesic and anaesthetic  effect of intrathecal MgS0₄ added to bupivacaine for spinal anaesthesia in patients undergoing lower extremity orthopaedic surgery.

Methods

Sixty ASA I or II adult patients undergoing lower extremity orthopaedic surgery were randomly allocated in a double blinded fashion into two groups of thirty each. Group A received 3.0 ml of 0.5% hyperbaric bupivacaine with  0.15 ml of 50% MgSO₄. Group B received 3.0 ml of 0.5% hyperbaric bupivacaine with 0.15 ml of NS. Onset of sensory and motor block as well as time to attain highest level of sensory block were recorded. Duration of sensory and motor block along with duration of spinal anaesthesia were also assessed. Any adverse effects were noted and treated.

Results

Duration of sensory and motor block along with duration of   spinal anaesthesia were prolonged in patients of MgSO₄ but were not statistically significant with p-value of 0.33, 0.23 and 0.68 respectively.  Onset of anaesthesia, requirement of rescue analgesics, haemodynamic parameters and adverse effects were comparable between two groups.

Conclusion

In patients undergoing lower extremity orthopaedic surgery the addition of 75mg of MgSO₄ to intrathecal bupivacaine did not prolong the duration of sensory block, spinal anaesthesia nor decreased postoperative analgesic consumption without any additional side effects.

Keywords: Bupivacaine, Intrathecal Magnesium Sulfate, Spinal Anaesthesia