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Eur J Cardiothorac Surg 2005;27:733-734
© 2005 Elsevier Science NL
Letter to the Editor |
a Department of Thoracic Surgery, Yedikule Teaching Hospital for Chest Diseases and Thoracic Surgery, Istanbul, Turkey
b Department of Chest Diseases, Yedikule Teaching Hospital for Chest Diseases and Thoracic Surgery, Istanbul, Turkey.
Received 7 December 2004; received in revised form 21 December 2004; accepted 23 December 2004.
* Corresponding author. Address: Cami Sok. Muminderesi Yolu.No:32/22, Sahrayicedid. Kadikoy, 81080 Istanbul, Turkey. Tel: +90 216 411 36 75; fax: +90 212 411 66 51. (E-mail: aturna{at}tnn.net).
Key Words: Lactate dehydrogenase • Pulmonary resection • Complication • Lung cancer
We are delighted that our article [1] attracted the colleagues of ours like you and, we appreciate your inputs.
Firstly, since more than one complication was recorded in some patients, total of 61 complications (minor and major) were documented in 49 patients (Table 1).We agree that, some of the mentioned complications were not purely ‘pulmonary’. However, it would have been not fair to exclude some morbidities such as supraventricular dysrythmia and pulmonary embolism, because they were reported to be strongly correlated with the surgery of pulmonary resection [2,3]. Moreover, there were 18 complications (not 25) reported in the article which could be claimed to be not pulmonary. These complications occurred in 11 patients (10.1%) since some patients developed multiple complications. Of these, only 4 patients (3.7%) developed single cardiac complication.
We did not know the reason of the observed predictive power of LDH level. However, we think that postoperative hemorrhage is not necessarily due to technical error during surgery (unless we mention surgical ‘accident’ causing massive bleeding during surgery as it was not recorded as a postoperative complication) and it is very difficult to predict before or during operation and re-exploration was reported to be required in 3.7% of patients[4]. Although it is too early to draw a conclusion from our study, it could be proposed that, tissue hypoxia and inflammatory process could be associated with higher LDH and bleeding tendency since the reduction of pyruvate by NADH to form lactate is catalyzed by LDH.
We stated in the beginning of the study that, forced expiratory volume in first second (FEV1) have been associated with increased postoperative mortality in most but not all studies. These two studies are only studies who questioned the clinical usefulness of this test. Despite their inherent limitations, the studies provided us evidence-based skepticism which must not be overlooked.
It was reported in our study that, the cut-off value of LDH was found to be 320 U/l.
The age, oxygen saturation, FEV1, VC, arterial pCO2 and pO2 levels were the clinical parameters of our consecutively resected patients with non-small cell lung cancer. There could be some differences between the demographic variables of the patients from United States (from the references given by the authors) and those from our center. Our data are reachable by Olgac et al., since we all work at the same institution.
We excluded the patients who underwent neoadjuvant therapy (n=3;2.8%)because the possible effects of the therapy on complications and LDH were unknown.
Regarding the statistical point, logistic regression is commonly used when the independent variables include both numerical and nominal measures and the outcome variable is binary (dichotomous) [5]. From the technical point of view, we conclude that, the use of logistic regression was appropriate. As it is indicated in ‘Materials and Methods’ section, to avoid multicollinearity, only one variable set of variables (not all of them) with a correlation coefficient >0.5 (i.e. alkaline phosphatase level, hemoglobin, serum LDH and arterial pCO2)was used in the multivariate analysis. Its use was also not inappropriate [5].
Finally, we appreciate the disagreement of Olgac and colleagues that, they would not agree with their suggestion to prolong the intensive care unit (ICU) stay -regardless of other parameters- for additional one day in patients with higher LDH levels. We also agree that, larger studies are warranted to define higher LDH level as a sole predictor of pulmonary complications and to disclose mechanism of action of the observed effect. Nevertheless, we are quite confident that, our retrospective study, despite its inherent limitations, nicely showed that, patients with higher preoperative LDH deserves more attention in terms of postoperative morbidity. Moreover, our study could become an ethical basis of further randomized studies.
References
lçgün A, Metin M, Sayar A, Gürses A. Lactate dehydrogenase levels predict pulmonary morbidity after lung resection for non-small cell lung cancer. Eur J Cardiothorac Surg. 2004;26:483-487.
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