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Rev. Bras. Anestesiol. vol.59 no.3 Campinas May/June 2009
LETTERS TO THE EDITOR
use of the Tobin Index on mechanical ventilation weaning after general anesthesia
(Rev Bras Anestesiol, 2007;57:592-605)
Luiz Alberto Forgiarini Junior I; Adriane Dal Bosco II; Alexandre Simões Dias III
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)
IIPhysical therapist; Kinesiology specialist by UFRGS; Master's Degree in Internal Medicine by UFRGS; Professor of the Centro Universitário Metodista - IPA
IIIPhysical 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
To the Editor,
First, we would like to congratulate the authors for the article "Evaluating the use of the Tobin index on mechanical ventilation weaning after general anesthesia" published in this journal 1. The subject is extremely important for clinical decisions of Intensive Care Units (ICU) professionals and represents a reference for the adequate transition from mechanical ventilation and spontaneous ventilation after general anesthesia.
Some considerations should be made regarding the procedures undertaken by the investigators in the study. The authors observed that patients with postoperative Tobin index between 80 and 100 c.L. -1min-1 had a higher risk of clinical intercurrences post-extubation. However, according to the Brazilian Society of Pneumology the term weaning refers to the transition from mechanical to spontaneous ventilation in patients on invasive ventilation for more than 24 hours 2. Therefore, in this study weaning was not done, patients were simply extubated.
As for the individuals included in the study, the population was heterogeneous, which was demonstrated by the significant differences between both groups regarding age, weight, 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 complications 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.
01. Mantovani NC, Zuliani LM, Sano DT, Waisberg DR, Silva IF, Waisberg J. - Avaliação da Aplicação do Índice de Tobin no Desmame da Ventilação Mecânica após Anestesia Geral. Rev Bras Anestesiol 2007;57:592-605. [ Links ]
02. III Consenso Brasileiro de Ventilação Mecânica. J Pneumol 2007;3(Supl. 2). [ Links ]
03. Saad AI, Zambom L - Variáveis clinicas de risco pré-operatório. Rev Ass Méd Bras 2001;47:117-124. [ Links ]
04. Doyle RL - Assessing and modifying the risk of postoperative pulmonary complications. Chest 1999;115:77s-81s. [ Links ]
05. Smetana GW - Preoperative pulmonary evaluation. N Eng J Med 1999;340:937-944. [ Links ]