Sir: We read with interest the article published by Dr. Heller and colleagues.1 Although the authors are to be commended for their aim of conducting the first prospective, randomized, double-blind trial in plastic surgery on the effect of continuous local anesthetic infusion after a relatively standardized surgical procedure, they do not state whether it was the same surgeon who performed the procedures. Despite the fact that the surgical procedure was similar, apparently, different surgeons were involved in this study. If the attempt was to standardize the procedure, the authors might have thought to standardize even the way such a procedure was performed. In fact, plastic surgeons agree that different surgeons may create different degrees of “damage” and discomfort to patients, even if they are performing the same procedure. In addition, it is interesting that the results of this study contrast with most of the evidence available in the literature as to the effect of local anesthetic infusion on opioid requirements, opioid side effects, and other important clinical and surgical endpoints. Moreover, there are several issues with both the design of the study and the statistical analysis regarding a prospective, randomized, double-blind trial. As for study design, the major issue is that there is no reference to any sample size calculation. This study does not appear to be adequately powered. In fact, for a particular finding to be claimed as significant (or not), the study must have enough power. In this particular case, assuming a morphine-sparing effect of 24.1 percent in the continuous infusion pump group after the first postoperative day2 (i.e., 26.5 mg calculated from the average value of 110 mg considering a consumption of 1.65 mg/kg3), more than 100 patients per group would have been required (considering the standard α error of 0.05 and a power of 0.8). Another critical point is the statistical analysis. The importance of nonlinear mixed-effects modeling in pain studies has been recently reaffirmed.4 It is of critical importance to use a method that accounts for both interindividual variability (e.g., unique sensitivity to pain), with the ability to characterize the time course of pain in different patients, and intraindividual variability (various sources of “noise”) as critically as in pain trials. Although this study is extremely interesting for plastic surgeons, appropriate statistical analysis of data from trials is crucial for adequate conclusions, especially in situations similar to that of the present study, where postoperative pain and patients’ comfort and length of hospital stay (crucial topics in plastic surgery) are addressed. We hope our suggestions will be useful to other authors who will be involved in similar studies in the future. Luca La Colla, Jr. Department of Anesthesiology Vita-Salute San Raffaele University School of Medicine IRCCS San Raffaele Alberto Mangano Vita-Salute San Raffaele University School of Medicine IRCCS San Raffaele Alessandro Mangano University of Milan Dental School Andrea Albertin Department of Anesthesiology IRCCS Multimedica Sesto San Giovanni Milan, Italy DISCLOSURE None of the authors has any conflict or financial interest with regard to the issue discussed in this letter.