Letter to the Editor

We are pleased to receive Dr. Eric B. Rosero's¹ editorial comments regarding the trial: “Randomized cross-over clinical trial comparing two pharmacokinetic models of propofol using entropy indexes”.²

One of the drawbacks of monitoring depth of anesthesia is that the records are usually contaminated with physiological and external artifacts; the reconstruction of a biological signal that accurately represents the relevant biological information is not an easy task. However, the Entropy module³ includes a pre-processing step that minimizes the introduction of noise into the signals recorded.

There are challenges inherent to the design of crossover trials but it is unlikely that the period effect occurred because the length of time of the surgical procedure was limited to maximum two hours. Given the type of procedure, during that time there were no volume exchanges or relevant changes in the physiological variables such as temperature and other hemodynamic conditions. It should be kept in mind that in terms of the carry-over effect, the washout period shall be enough to prevent the drug from having any pharmacodynamic effects and from interfering with the second treatment period.

With regards to the possibility of experiencing intraoperative recall upon the discontinuation of the propofol infusion (constant remifentanil infusion), no intraoperative awareness was reported during the patients’ follow-up.

Funding comment

The authors did not receive any sponsorship to produce this article.

Conflicts of interest

The authors have no conflicts of interest to declare.