The Effect of Systemic Magnesium on Postsurgical Pain in Children Undergoing Tonsillectomies: A Double-Blinded, Randomized, Placebo-Controlled Trial

Benzon, Hubert A. MD, MPH*; Shah, Ravi D. MD*; Hansen, Jennifer MD*; Hajduk, John BS*; Billings, Kathleen R. MD*; De Oliveira, Gildasio S. Jr. MD, MSCI; Suresh, Santhanam MD*

doi: 10.1213/ANE.0000000000001028
Pain Medicine: Research Report

BACKGROUND: Tonsillectomy is a frequently performed surgical procedure in children; however, few multimodal analgesic strategies have been shown to improve postsurgical pain in this patient population. Systemic magnesium infusions have been shown to reliably improve postoperative pain in adults, but their effects in pediatric surgical patients remain to be determined. In the current investigation, our main objective was to evaluate the use of systemic magnesium to improve postoperative pain in pediatric patients undergoing tonsillectomy. We hypothesized that children who received systemic magnesium infusions would have less post-tonsillectomy pain than the children who received saline infusions.

METHODS: The study was a prospective, randomized, double-blinded, clinical trial. Subjects were randomly assigned using a computer-generated table of random numbers to 1 of the 2 intervention groups: systemic magnesium infusion (initial loading dose 30 mg/kg given over 15 minutes followed by a continuous magnesium infusion 10 mg/kg/h) and the same volume of saline. The primary outcome was pain scores in the postanesthesia care unit (PACU) measured by FLACC (Face, Legs, Activity, Cry, Consolability) pain scores. Pain reduction was measured by the decrement in the area under the pain scale versus 90-minute postoperative time curve using the trapezoidal method. Secondary outcomes included opioid consumption in the PACU, emergence delirium scores (measured by the pediatric anesthesia emergence delirium scale), and parent satisfaction.

RESULTS: Sixty subjects were randomly assigned and 60 completed the study. The area under pain scores (up to 90 minutes) was not different between the study groups, median (interquartile range [IQR]) of 30 (0–120) score × min and 45 (0–135) score × min for the magnesium and control groups, respectively (P = 0.74). Similarly, there was no clinically significant difference in the morphine consumption in the PACU between the magnesium group, median (IQR) of 2.0 (0–4.44) mg IV morphine, compared with the control, median (IQR) of 2.5 (0–4.99) mg IV morphine (P = 0.25). The serum level of magnesium was significantly lower in the control group than in the treatment group at the end of the surgery (P < 0.001).

CONCLUSIONS: Despite a large number of studies demonstrating the efficacy of systemic magnesium for preventing postsurgical pain in adults, we could not find evidence for a significant clinical benefit of systemic magnesium infusion in children undergoing tonsillectomies. Our findings reiterate the importance of validating multimodal analgesic strategies in children that have been demonstrated to be effective in the adult population.

From the *Department of Anesthesiology, Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern University, Chicago, Illinois; and Department of Anesthesiology, Northwestern University, Chicago, Illinois.

Accepted for publication September 2, 2015.

Funding: Supported, in part, by 8UL1TR000150 from the National Center for Advancing Translational Sciences (NCATS) and National Institutes of Health.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Gildasio S. De Oliveira, Jr., MD, MSCI, Department of Anesthesiology, Northwestern University, 241 East Huron St., F5-704, Chicago, IL 60611. Address e-mail to

© 2015 International Anesthesia Research Society