Preemptive use of epidural magnesium sulphate to reduce narcotic requirements in orthopedic surgery

Background and objectives
As pain is one of the most common problems challenging the anesthetist, and as regional anesthesia is a safe, inexpensive technique with the advantage of prolonged postoperative analgesia. Also, we all know that Magnesium is the fourth most plentiful cation in the body with antinociceptive properties arising from being the natural physiological calcium antagonist and the antagonism to N-methyl--aspartate (NMDA) receptor. Thus, the study is a prospective, randomized, double-blind study designed to evaluate analgesic efficacy of magnesium sulphate when added to epidural bupivacaine in patients undergoing orthopedic surgery in the lower limb.
Methods
After approval of the ethical committee and informed written consent 60 patients ASA I and II, undergoing orthopedic surgery in the lower limb were enrolled to receive either bupivacaine 0.5% or bupivacaine 0.5% plus magnesium sulphate 50 mg as an initial bolus dose followed by a continuous infusion of 10 mg/h as intraoperative epidural analgesia. Postoperatively, all patients were equipped with a patient-controlled epidural analgesia device. Heart rate, mean arterial pressure, oxygen saturation, respiratory rate, pain assessment using a visual analogue scale (VAS), sedation score, the first time patient ask for analgesics and postoperative fentanyl consumption were recorded.
Results
VAS was significantly less in the magnesium group during 15 and 30 min intra-operatively and in the first and third hour post-operatively. The postoperative rescue analgesia, as well as the PCEA fentanyl consumption, was significantly reduced in the magnesium group.
Conclusion
Co-administration of epidural magnesium provides better intraoperative analgesia as well as the analgesic-sparing effect on PCEA consumption without increasing the incidence of side-effects.