Revista Brasileira de Anestesiologia 383 Vol. 59, No 3, Maio-Junho, 2009
CARTAS AO EDITOR / LETTERS TO THE EDITOR
smoking, and anesthetic risk. We suggest that population pairing should have been made according to the operative risk as determined by the classification of the American Society of Anesthesiologist (ASA) since high risk patients (mostly in group II) could have a greater incidence of complications and worse predictive failure index, which was seen in the study. Not using the ASA classification could have interfered with the variables of the Tobin index, length of stay in the post-anesthetic care unit (PACU), and clinical intercurrences after extubation.
Thus, the results of the study could have been influenced by the significant difference in the characteristics of the study population, such as age, weight, and smoking. According to Saad, several factors increase the risk of pulmonary com-plications after abdominal surgeries, and obesity can cause a reduction in coughing effectiveness, basal atelectasis, progressive hypoxia, and accumulation of pulmonary secretions 3. Analyzed isolatedly, age does not constitute an isolated postoperative risk factor; however, it can interfere with lung function when associated with other factors 4. Smoking also constitutes a risk factor for postoperative complications even in individuals who do not have lung diseases and the patient should stop smoking at least eight weeks before surgery 5.
Although there are controversies in the scientific literature on the use of predictive indexes, this study presents relevant clinical information for the different professionals who work with this type of patient.
Luiz Alberto Forgiarini Junior 1, Adriane Dal Bosco 2, Alexandre Simões Dias 3
1. Physical therapist. Graduated from the Centro Universitário Metodista – IPA; Enrolled on the Post-Graduate Program (Doctorate) in Lung Diseases of the Universidade Federal do Rio Grande do Sul (UFRGS); Researcher of the Physiology and Experimental Hepatology Laboratory of the Clínicas de Porto Alegre (HCPA)
2. Physical therapist; Kinesiology specialist by UFRGS; Master’s Degree in Internal Medicine by UFRGS; Professor of the Centro Universitário Metodista – IPA
3. Physical therapist; Physical Therapy Professor at Centro Universitário Metodista – IPA; Master’s Degree in Physiology by UFRGS; Physiology Doctorate by UFRGS; Researcher of the Physiology and Experimental Hepatology Laboratory of HCPA; Rehabilitation and Inclusion Master’s Assay Coordinator – IPA
REFERÊNCIAS – REFERENCES
01. Montovani NC, Zuliani LM, Sano DT et al. - Avaliação da aplica-ção do índice de tobin no desmame da ventilaaplica-ção mecânica após anestesia geral. Rev Bras Anestesiol 2007;57:592-605. 02. III Consenso Brasileiro de Ventilação Mecânica. J Pneumol
2007;3(Supl. 2).
03. Saad AI, Zambom L - Variáveis clinicas de risco pré-operatório. Rev Ass Méd Bras 2001;47:117-124.
04. Doyle RL - Assessing and modifying the risk of postoperative pulmonary complications. Chest 1999;115:77s-81s.
05. Smetana GW - Preoperative pulmonary evaluation. N Eng J Med 1999;340:937-944.
Réplica
Senhora Editora:
Agradecemos os importantes comentários de Forgiarini Jr e col. em relação ao nosso estudo: Avaliação da aplicação do índice de Tobin no desmame da ventilação mecânica após anestesia geral 1.
Forgiarini Jr e col. sugerem o pareamento amostral dos in-divíduos pelo risco operatório segundo a classificação da American Society of Anesthesiologists (ASA). Justificam essa iniciativa pelo fato de que doentes de alto risco poderiam apresentar maior número de complicações e pior índice preditor de insucesso. Ocorre que os doentes desse estu-do foram dividiestu-dos em estu-dois grupos de acorestu-do com o valor do índice de Tobin e, portanto, esse índice foi considerado a variável estudo em relação à qual todas demais foram comparadas, inclusive o escore da ASA. Mesmo com a pro-nunciada diferença do escore da ASA elevado entre os dois grupos (ASA III ou IV de 10% no grupo I versus 50% no gru-po II), não houve diferença significante na análise de regres-são logística univariada, indicando que esse escore não influenciou o risco de insucesso da extubação.
Embora a homogeneidade das variâncias fosse verificada pelo teste de Levene e a normalidade pelo teste de Kolmo-gorov-Smirnov, mesmo uma diferença significativa das vari-áveis da amostra não inviabilizaria os resultados do estudo, uma vez que a variável estudada (índice de Tobin com valor de corte < 80 c.L.-1.min-1 ou ≥ 80 c.L-1.min-1) foi quem definiu os dois grupos de doentes. A aplicação da análise de regres-são logística univariada e multivariada identificou três variá-veis significantes para a ocorrência de complicações pós-extubação (idade, peso corpóreo e tabagismo), sendo variáveis independentes a idade e o peso corpóreo. A idade avançada traz consigo redução, por vezes subclínica, da ca-pacidade funcional de órgãos (enfisema senil, nefrosclerose benigna, ateromatose coronária) que indiscutivelmente au-mentarão os riscos de complicações, inclusive aquelas re-lacionadas com a extubação. Os riscos de complicações pós-extubação de doentes obesos e por tabagismo foram adequadamente apontados pelos próprios missivistas e confirmados pelos resultados do presente estudo.
Para concluir, destacamos que os resultados obtidos por esse estudo são produtos de método rigorosamente apli-cado e agradecemos a leitura atenta, os esclarecimentos e os comentários pertinentes de Forgiarini Jr e col.
1 - Mantovani NC, Zuliani LM, Sano DT, Waisberg DR, Silva IF, Waisberg J. Avaliação da Aplicação do Índice de Tobin no Desmame da Ventilação Me-cânica após Anestesia Geral. Rev Bras Anestesiol, 2007; 57: 592 – 605.
384 Revista Brasileira de Anestesiologia Vol. 59, No 3, Maio-Junho, 2009
CARTAS AO EDITOR / LETTERS TO THE EDITOR
Reply
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 Ame-rican 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
multiva-riate logistic regression analysis identified three significant parameters for the development of post-extubation compli-cations (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 methodo-logy 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 Jaques Waisberg
REFERÊNCIAS – REFERENCES
