Methadone, Magnesium Not Beneficial for Post-Spinal Infusion Pain

Preliminary data shows no significant difference in postoperative opioid consumption with a single intraoperative dose of methadone or magnesium bolus versus remifentanil alone following posterior spinal fusion, according to a study presented here at ANESTHESIOLOGY 2015, the Annual Meeting of the American Society of Anesthesiologists (ASA).

Furthermore, bolus dosing of magnesium may interfere with monitoring of motor evoked potentials without offering any analgesic advantages.

Using anaesthesia for surgical correction of scoliosis in adolescents is complicated and poses many intraoperative and postoperative challenges. Posterior spinal fusion is associated with substantial postoperative pain and opioid consumption, often exceeding those of other major surgeries.

Remifentanil is considered an excellent option for intraoperative analgesia due to its potency and short context sensitive half-life. However, it has also been associated with acute opioid tolerance even after a single procedure.

Studies have demonstrated higher postoperative opioid requirements in patients receiving intraoperative continuous remifentanil infusion compared with patients receiving intraoperative morphine bolus dosing alone. Researchers have also posited that remifentanil may lead to hyperalgesia due to its activity at the N-methyl-D-aspartate receptor (NMDA). Both methadone and magnesium are non-competitive NMDA receptor antagonists and have been used in many different surgical procedures to decrease postoperative narcotic consumption.

For the current prospective, randomised controlled trial, Hiromi Kako, MD, Nationwide Children’s Hospital, Columbus, Ohio, and colleagues evaluated the efficacy of either intraoperative magnesium or methadone on postoperative pain control in 33 patients aged 12 to 18 years presenting for posterior spinal fusion for idiopathic scoliosis. There was no difference in the patient demographics among the 3 groups.

Patients were randomised to remifentanil infusion alone, remifentanil infusion plus a single intraoperative dose of intravenous methadone, or remifentanil infusion plus a magnesium bolus followed by an infusion. The remainder of the anaesthetic care included desflurane titrated to maintain intraoperative anaesthesia, hydromorphone during emergence and in the post-anaesthesia care unit, and patient-controlled analgesia with hydromorphone for postoperative analgesia.

There was no significant difference between the 3 groups in postoperative opioid consumption or average pain scores. One patient in the control group developed to postoperative ileus.

[Presentation title: A Prospective, Randomized Controlled Study of Analgesia Following Posterior Spinal Fusion: Methadone vs Magnesium. Abstract A3190]