The effect of magnesium added to levobupivacaine for femoral nerve block on postoperative analgesia in patients undergoing ACL reconstruction

PURPOSE: The aim of this prospective randomised double-blind study is to investigate the effect of magnesium added to local anaesthetics on postoperative VAS scores, total opioid consumption, time to first mobilisation, patient satisfaction and rescue analgesic requirements in arthroscopic ACL reconstruction surgery. METHODS: A total of 107 American Society of Anaesthesiologists physical status grade I and II patients between 18 and 65 years of age who were scheduled to undergo elective anterior crucial ligament (ACL) reconstruction with hamstring autografts were enrolled in the study. The patients were randomly allocated to Groups L (n = 51) and LM (n = 56) using the closed-envelope method. Group LM was administered 19 ml of 0.25% levobupivacaine and 1 ml of 15% magnesium sulphate, while Group L was administered 20 ml of 0.25% levobupivacaine for femoral blockade. General anaesthesia was administered using laryngeal airway masks following neural blockade in both groups. The patients were evaluated for heart rate and mean arterial pressure, oxygen saturation, visual analogue score (VAS), verbal rating scale (VRS), rescue analgesic requirements, total opioid consumption, side effects and time to first mobilisation at the 1st, 2nd, 4th, 6th, 12th and 24th hours postoperatively. RESULTS: There was no statistically significant difference in terms of demographic data, mean arterial pressure, heart rate or oxygen saturation between groups. The area under the curve VAS and VRS scores were lower at 4, 6, 12 and 24 h in Group LM (p = 0.001, p = 0.016, respectively). The rescue analgesic requirement and the total opioid consumption were significantly lower in Group LM (p = 0.015, p = 0.019, respectively). The time to first mobilisation and the Likert score (completely comfortable; quite comfortable; slight discomfort; painful; very painful) were higher, and the block onset time was lower in Group LM (p = 0.014 and p = 0.012, respectively). There was no difference in terms of side effects. CONCLUSIONS: The addition of magnesium to levobupivacaine prolongs the sensory and motor block duration without increasing side effects, enhances the quality of postoperative analgesia and increases patient satisfaction; however, the addition of magnesium delays the time to first mobilisation and decreases rescue analgesic requirements.