Magnesium prolongs the duration of analgesia after a bupivacaine fascia iliaca compartment block

Background A fascia iliaca compartment block (FICB) performed in patients with hip fracture before spinal anesthesia can help facilitate patients’ positioning and reduce the postoperative analgesic requirements; however, the duration of FICB is limited to the early postoperative period. Magnesium has been shown to prolong the duration of analgesia when coadministered with local anesthetics for peripheral nerve blockade. Objectives To determine the effect of the addition of magnesium sulfate to bupivacaine on the duration of analgesia provided by FICB in patients undergoing surgery hip fracture. Methods Forty-four patients (50–79 years old) scheduled for hip fracture repair were randomized to either group B, which received FICB with 30ml bupivacaine 0.25%, or group MB, which received FICB with 30ml bupivacaine 0.25% containing 250mg magnesium sulfate. Sensory blockade in the anterior thigh (supplied by the femoral nerve) and pain scores at rest and on movement were assessed 30 min after FICB. Then, the patients were transferred to the operating room, instructed to sit for spinal anesthesia, and satisfaction with the sitting position was recorded (yes/no). Postoperatively, pain scores at rest and on movement at 4, 8, 12, and 24 h after FICB, time to first analgesic requirement, total tramadol given in the first 24 h after FICB, and the occurrence of adverse effects were also recorded and compared between the two groups. Results Patients who received magnesium had a longer time to first analgesic administration, lower pain scores on movement at 8, 12, and 24 h after the FICB, and lower tramadol consumption for postoperative pain. No complications related to FICB were reported. Conclusion The addition of magnesium to bupivacaine for FICB significantly prolongs the duration of analgesia and reduces opioid demand, without side effects.