Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.59 no.3 Campinas May/June 2009
LETTERS TO THE EDITOR
To the Editor
We acknowledge the important comments of Forgiarini Jr et al. regarding our study: Evaluating the use of the Tobin index on mechanical ventilation weaning after general anesthesia 1.
Forgiarini Jr et al. suggested paring patients according to the operatory risk determined by the classification of the American Society of Anesthesiologist (ASA). Their justification was that the incidence of complications of high-risk patients could be higher and the predictive index of failure could be worse. However, patients in this study were divided into two groups according to the Tobin index and, therefore, this index was considered the study parameter and all other parameters were compared to it, including the ASA classification. Even with the important difference in elevated ASA score between both groups (10% of patients in group I were ASA III or IV versus 50% in group II), univariate logistic regression analysis did not detect statistically significant differences, indicating that this score did not affect the risk of extubation failure.
Although the homogeneity of variances was verified by the Levene test and the normality by the Kolmogorov-Smirnov test, even a statistically significant difference among the parameters of the study population would not invalidate the results of the study, since it was the study parameter (Tobin index with a cutting point of < 80 c.L.-1min-1 or > 80 c.L.-1min-1) that defined both groups of patients. Univariate and multivariate logistic regression analysis identified three significant parameters for the development of post-extubation complications (age, weight, and smoking), of which age and weight were independent parameters. Aging is associated with reduction often subclinical in the functional capacity of the organs (emphysema, benign nephrosclerosis, coronary artery atheroma), which undoubtedly increase the risk of complications, including those associated with extubation. The risks of post-extubation complications in obese patients and smokers were adequately explored by Forgiarini Jr et al. and confirmed by the results of our study.
To conclude, we would like to emphasize that the results of this study are a consequence of a strictly applied methodology and we thank Forgiarini Jr et al. for their carefully reading of our study, the explanations, and pertinent comments.
Nara de Cássia Mantovani
Lúcia Maria Martins Zuliani
Daniela Tiemi Sano
Daniel Reis Waisberg
Israel Ferreira da Silva