Factors increasing blood transfusion in open heart surgery

We would like to congratulate the authors for their study [1]. First, in this study, which is stated to be conducted retrospectively, it is really interesting to be able to standardize the way 180 patients underwent pulmonary functional test (PFT) in terms of the factors affecting blood transfusion. Although the PFTs performed in the patients make this study more valuable than other similar studies in examining the role of chronic obstructive pulmonary disease (COPD) as a risk factor for transfusion, information as to why and on which patients PFTs were performed should be stated. Otherwise, questions may arise on how such a homogenous patient group was obtained. No statistical difference was found between the COPD and non-COPD patients in terms of the crucial preoperative parameters for blood transfusion such as aspirin, coumadin, antiplatelet and adenosine diphosphate receptor inhibitor usage, preoperative haematocrit values, emergency surgery rates, postoperative heparin, coumadin, aspirin and clopidogrel usage, making the study one of great value. As far as can be seen, two parameters showing a significant difference between the groups were smoking and cardiopulmonary bypass (CPB) durations. How would the authors explain that durations are longer in the non-COPD group compared with the COPD group, while proportion of subjects requiring a blood transfusion was greater in the COPD group, although the latter was not statistically significant? The reason for asking this is because present knowledge shows that the rates of blood transfusion increase with the prolongation of CPB duration [2, 3]. In addition, is there any difference between both the groups in terms of redo cases? Redo cases are known to cause more bleeding, and a greater amount of blood and blood products is used in these patients. What are the criteria of blood transfusion in the patients? Is there any difference between both the groups if these criteria had included the postoperative drainage quantity? We believe that this well-planned and standardized study would be much more perfect if the above-mentioned considerations could be clarified.