Effects of lidocaine and magnesium sulfate in attenuating hemodynamic response to orotracheal intubation: a single-center, prospective, double blind, randomized study

It was with great pleasure that I read the article “Effects of lidocaine and magnesium sulfate in attenuating hemodynamic response to orotracheal intubation: a single-center, prospective, double blind, randomized study”.¹ Concerned to clarify some points related to the statistical analysis and conclusion; here are some considerations to the authors:

1. The authors report a discrete statistical difference and this does not allow the article's reader to come to conclusions: “There was a statistically significant increase in SBP (p = 0.018) and DBP (p = 0.0467) values measured post-TI (Fig. 2), but of little clinical importance”. The values should have been demonstrated in text because, as shown in Fig. 2, it is not possible to capture its magnitude, so that the lack of clinical importance does not represent absence of biological relevance;

2. The data were partially or totally analyzed over time, and the patients were also submitted to anesthetics in addition to the medications tested, which may be in addition or not. It is known that magnesium sulfate has a prolonged clinical effect after venous use, whereas lidocaine has a short protective effect compared to magnesium. Thus, there are two factors that must be considered in this statistical analysis: time and treatment. The best statistical test to perform in this situation is two-way ANOVA.² The results analyzed as they are in the text may be erroneously positive and the possibility of a type I error in this research is clearly perceived;

3. If the authors consider the use of the Student's t test as correct, or more appropriately in some cases the Mann-Whitney U test, according to the text, they should have corrected the p value with the procedure for multiple correction of hypothesis tests, instead of considering only 5% as the level of significance in all analyzes. The possibility of having a positive result in the statistical analysis occurring at random is 5%. The p-value correction would have reduced the probability of a random occurrence of the statistical result. Thus, the possibility of type I error in this research is clear;

4. The objective described by the authors was “to compare the effects of intravenous administration of magnesium sulfate versus lidocaine on this reflex hemodynamics after laryngoscopy and orotracheal intubation”. The authors' conclusion was “magnesium sulfate and lidocaine have good efficacy and safety in hemodynamic control during laryngoscopy and intubation”, which is not in line with the proposed objective. It is necessary that the authors relate what were the efficacy variables and also the safety variables so that the conclusion is better understood. Noteworthy, the term efficacy should generally be used in research whose execution conditions are ideal, as with laboratory studies. This term should also be reviewed by the authors, effectiveness is the term suggested;

5. Finally, I leave as a recommendation the observation to the authors that there are larger doses, equally safe and equally effective, that could have been tested in this clinical trial and increased the degree of information related to the topic.³

I congratulate the authors for the brilliant initiative, while celebrating at the same time the possibility of creating this line of research in anesthesia in Brazil. Thank you for the opportunity to contribute to this topic.

References

• ¹
  Mendonça FT, Queiroz LMGM, Guimarães CCRG, et al. Os efeitos da lidocaína e do sulfato de magnésio na atenuação da resposta hemodinâmica à intubacão orotraqueal: estudo unicêntrico, prospectivo, duplamente encoberto e aleatorizado. Rev Bras Anestesiol. 2016. Em processo de publicação.
• ²
  Kim HY. Statistical notes for clinical researchers: two-way analysis of variance (ANOVA) - exploring possible interaction between factors. Restor Dent Endod. 2014;39:143-7.
• ³
  Barbosa LT, Jucá MJ, et al. Applications of magnesium sulfate in obstetrics and anesthesia. Rev Bras Anestesiol. 2010;60:104-10.

Publication Dates

• Publication in this collection
  Nov-Dec 2017