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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094On-line version ISSN 1806-907X

Rev. Bras. Anestesiol. vol.59 no.2 Campinas Mar./Apr. 2009 



Comparative study of the postoperative analgesic efficacy of 20 mL of 0.5, 0.75, and 1% ropivacaine in posterior brachial plexus block
(Rev Bras Anestesiol, 2008;58:431-439)



To the Editor,

We read the study 1 published by the Revista Brasileira de Anestesiologia on the efficacy of anesthesia with great interest. We would like to congratulate the authors for the excellent work. To clarify some methodological aspects, we would like to make a few comments:

a) Regarding the objective: in the summary, the authors stated that the objective was to determine "which concentration" of the local anesthetic used in the brachial plexus block would provide more prolonged analgesia, but in the introduction the authors stated that the objective was to evaluate "if using high concentrations of local anesthetic in the posterior brachial plexus block" would promote more prolonged analgesia. It is recommended specifying the real objective of the study because, after reading the paper, the last objective seemed more adequate for this type of study, since they wished to know which of the three concentrations would last longer.

b) The authors did not specify the parameters used to calculate the size of the study population or the level of p considered non-significant. One should not forget that the size of the sample is inversely proportional to the final value of p and, therefore, the smaller the population the higher the value of p. The absence of differences among the study groups could result from a real lack of difference or it could be a reflex of the small number of patients, compromising the statistical power of the study. Besides, it seemed that all patients received NSAIDs and dypirone, which could also have contributed with supplementary analgesia in all groups, and this could be considered a confounding bias.

c) The term efficacy was used throughout the text; however, the tem efficiency was also used in the conclusion of the Discussion section. In epidemiology 2, efficiency is related with the cost, and this aspect was not explored in this study. The authors should have reported, in the discussion, what was considered in the analysis of the efficiency.

We did not intend to make disconnected critics, but to contribute with the authors for a better understanding of their results. We would like to congratulate the authors 1 due to the real need to use, in daily practice, what is more "effective" in favor of patients undergoing anesthesia.


Fabiano Timbó Barbosa, TSA, M.D.
André Luiz Leme Teixeira Pinto, TSA, M.D.
Rafael Martins da Cunha



01. Cruvinel MGC, Castro CHV, Silva YP et al. - Estudo comparativo da eficácia analgésica pós-operatória de 20 mL de ropivacaína a 0,5, 0,75 ou 1% no bloqueio de plexo braquial pela via posterior. Rev Bras Anestesiol, 2008;58:431-439.         [ Links ]

02. Fletcher RH, Fletcher SW - Epidemiologia Clínica Elementos Essenciais, 5ª ed, São Paulo, Artmed, 2006; 168-169.        [ Links ]

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