We are very thankful to Muñoz et al. for their interest in our recent article. 1We agree with their speculation that transfusion-related acute lung injury might be one of the various causes explaining prolonged mechanical ventilation. However, the relationship between transfusion and transfusion-related acute lung injury and mechanical ventilation is difficult to establish in cardiac surgery patients, who are known to be under the influence of many other causes of pulmonary dysfunction. 2For instance, the association between the number of units transfused and mechanical ventilation may be due to an overload of transfused units, thus favoring the occurrence of pulmonary edema.
In our series, platelet transfusion (as a dichotomous variable) was considered a risk factor for morbidity. However, in the preliminary multivariate analysis, patients transfused with platelets did not show a higher morbidity than those not receiving platelet transfusions. Therefore, platelet storage time was not considered necessary to investigate.
We demonstrated an association existing between nosocomial pneumonia and the number of erythrocyte concentrate units transfused, 3and between nosocomial pneumonia and length of storage of erythrocyte concentrate. 1This is not unexpected, though, as the potential deleterious effects of the storage time may multiply according to the number of units transfused.
We also agree that blood-saving programs and alternatives to allogeneic transfusion are needed. However, the applicability or effectiveness of many methods remains controversial, so preoperative autologous donation programs are effective in decreasing allogeneic blood transfusion but are costly and applicable to elective patients only. The effectiveness of acute normovolemic hemodilution is too unreliable to decrease the risk of allogeneic blood transfusion in elective cardiac surgical patients with normal cardiac function. 4Moreover, among the pharmacologic strategies for blood conservation, antifibrinolytics such as aprotinin are the only agents that have been shown to reduce the risk of mortality after cardiac surgery. 5
We believe that the judicious use of rational transfusion guidelines may still be the most simple and cost-effective means of blood conservation. However, blood consumption is still high and is unavoidable, thus justifying the need for studies designed to clarify the potential deleterious effects of blood transfusion, including storage.