Perioperative Role of Methadone in Adolescent Patients

To the Editor: We congratulate Sharma et al. for their study of pharmacokinetics of methadone and its effect on postoperative pain scores and opioid consumption.1We had a few questions and comments regarding their study. This study is primarily designed to evaluate the pharmacokinetics of methadone, and not its opioid-sparing effects. Lack of standardization of the intraoperative management and postoperative pain management may lead to multiple recognized and unrecognized confounding factors being unadjusted between the treatment groups. These confounding factors may be responsible for a lack of difference in the amount of postoperative opioid consumption between the controls and the three-methadone groups.2A randomized prospective pediatric study3and another study on posterior spinal fusion surgery patients4found a beneficial effect of methadone administration on postoperative opioid consumption and pain scores. This observational study may not have the power and design to look at the clinical effects of methadone in the postoperative period.The small sample size could lead to a Type II error, i.e. , acceptance of the null hypothesis when there exists a difference because of a lack of power to detect it. The authors have not mentioned a power analysis in the statistical methods. Based on the numbers presented in the study, i.e. , a mean postoperative opioid use of 275 mg in the control group with a SD of 75 mg, we estimate that a sample size of 22 patients would be needed in each of the four groups to have a power of 80% (with a α = 0.05) to show a decrease in opioid use of 75 mg between the groups with the largest and the smallest mean postoperative opioid consumption.