The replacement of blood losses in the critical patient through the transfusion of blood products has changed substantially in recent decades.1 Those in charge of deciding transfusion must consider that the inappropriate use of these products increases patient morbidity-mortality, and that blood products are moreover valuable and rather scarce.

Previous studies have shown that blood products are often not used properly, contributing to place patients at risk by exposing them to the potential complications of transfusion, such as transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), transfusion-related immunomodulation (TRIM) and infections – especially if transfusion is unnecessary or is secondary to transfusion error.2,3 On the other hand, needless transfusion seriously reduces the availability of blood products for those patients who really do need them.4 The World Health Organization (WHO) considers that transfusion should be regarded as a current healthcare resource which when used correctly as a therapeutic intervention is able to save lives. Nevertheless, knowing the potential complications of the procedure, unnecessary transfusion must be avoided, and alternatives should be used whenever possible. The health authorities, care providers and physicians are crucial for the prevention, early diagnosis and management of those clinical situations in which blood transfusion may prove necessary.2

The above is encompassed within the concept of Patient Blood Management (PBM),5 which stresses the importance of multidisciplinary programs for the optimization of erythropoiesis.6 In Spain, article 40 of Royal Decree (RD) 1088/20051,7 regulates the existence and functions of hospital and regional transfusion committees and centers, with the primary aim of ensuring the correct use of blood and its different components. However, despite the existence of such legislation, there is a notorious variability of prescription practices among different centers, possibly due to differences in their degree of implementation of the PBM programs.

Aging of the population, combined with age-related comorbidities and the increased use of antiplatelet drugs and anticoagulants among the elderly, could be related to an increase in transfusion rates in Spain. In contraposition to this, some studies have reported that despite these conditioning factors, the transfusion rates have not increased as expected,8 and this could be due to the more or less intense work of the hospital transfusion committees, which seek to ensure a more rational use of transfusion practices.

The most widely used transfusional threshold-defining parameter remains the hemoglobin (Hb) concentration,9,10 despite the fact that it is also one of the main factors conditioning inappropriate transfusions. In many cases the values proposed in the clinical practice guides are not followed.11 This situation is more patent in elderly patients, since there is no scientific evidence warranting the idea that higher Hb levels improve the survival or quality of life of these patients, and hence more restrictive transfusion practices in this particular population group appear to be the safest option.12

It is not clear whether there are differences in the transfusion criteria and in the number and percentage of critical patients subjected to transfusion among the different Spanish Intensive Care Units (ICUs). In this regard, it is reported that the predominant activities in the ICU are of a medical nature, and if we consider the existence of a group of such Units specialized in polytraumatized patients – which are the Units characterized by a high transfusion demand – we effectively have a defined potential source of transfusional variability. Furthermore, this same article underscores the idea that our ICUs usually have no protocols, and few hospitals have transfusion committees. In turn, in those centers that do have such committees, the latter do not usually generate standards, or these are of little relevance. All this contributes to further accentuate the possible differences in relation to transfusion policies among different hospitals.

We postulate that there may be important variability in this regard. The aim of the present «Transfusion day» study was to determine the epidemiology of transfusion practices in Spanish ICUs, and to identify the factors that influence their possible variability.

Vincent et al.12 reported a 26% transfusion rate among patients over 16 years of age, and other earlier studies have documented higher rates, such as the European ABC study, where the estimated transfusion rate among adults was 37%.13–21 In the present study, the blood transfusion rate did not exceed 10%. This low percentage may be explained in part by the bias inherent to our cross-sectional study design, where there is no patient follow-up from ICU admission to discharge – though the large number of patients included from an extensive sample of Spanish ICUs tends to minimize this bias. Furthermore, the transfusional threshold was very close to 7 g/dl of Hb, which suggests that this low transfusion rate may also be a consequence of a better transfusion policy in our country, thanks to correct operation of the committees that regulate the transfusion act as a result of implementation of the Royal Decree of 2005.7 On the other hand, an interesting finding in our series is that the highest transfusion rate did not correspond to the surgical patients, despite the fact that the scientific evidence points to these patients as those requiring more transfusions. In any case, it is true that 79.28% of the ICUs in our study were polyvalent Units, and the structure corresponding to the type of ICU may be related to the low transfusion rate in cardiological patients – where specialized ICUs represented 9.01% – or surgical patients.

Anemia was the most frequent laboratory test finding in the ICUs. On the third day of admission, anemia was present in a full 95% of the critical patients, and this caused a considerable proportion of them (30–75%) to receive at least one allogenic blood transfusion during admission.13–16 In any case, in clinical practice, blood transfusion seeks to increase oxygen supply and therefore alleviate tissue hypoxia. However, the hypothetical benefit of blood transfusion has not been firmly demonstrated.17 Few studies have described an increase in oxygen consumption following transfusion, and most of the articles in this field only document an increase in oxygen transport,18 reflecting independence between consumption and transport before blood transfusion. However, in patients with a positive dobutamine test,19 lactic acidosis20and septic cases,21,22 where oxygen consumption – transport dependency may exist, transfusion does not increase tissue oxygen consumption. Therefore, if there is no clear evidence of the efficacy of allogenic blood transfusion in reducing tissue hypoxia, there is likewise no clear evidence that transfusion improves patient survival. In our study, an increase in Hb concentration was recorded after blood transfusion, and the patients with anemia had a higher transfusion rate. However, the 24-h mortality rate was similar in transfused patients and non-transfused individuals (4.90% versus 2.41%; p = 0.070) – these results being consistent with the data described above.

On the other hand, variability in the transfusion of blood components is a situation constantly reflected in the literature. This circumstance may be explained by the fact that the patients differ in terms of severity or comorbidities, thus generating differences in the transfusion criteria, which are based fundamentally upon laboratory test data (Hb concentration), but also on patient age, reason for admission, hospital stay or the severity of the disease condition leading to admission in the first place.12

According to the findings of a national survey on transfusion practices in the ICU,23 patients usually receive 2–4 packed red blood cell units. While these figures may be adequate in the context of acute bleeding, they are excessive in critical patients with non-hemorrhagic anemia, as is seen in our own figures, with an average of 3.6 units. We also observe that there is not much confidence in the use of transfusion alternatives or in assuming a clear relationship between transfusion and mortality. With regard to such inadequacy of red cell transfusion (indicator 87) and red cell over-transfusion (indicator 88), work has been done in the intensive care setting (book of indicators of the SEMICYUC, 2017),24 though with scant real evidencing of the theory.

In the present study, differences were observed in the transfusion rates among the 111 hospitals conforming the sample. In effect, some hospitals had no patients subjected to transfusion in the 24-h period of the study, while in contrast other hospitals reported transfusion among all the patients admitted to the ICU – though in most centers the transfusion rates ranged between 5–20%. In this regard, the SANGUIS (Safer And Good Use of blood In Surgery) project has audited the transfusion practices in 7195 patients in 43 hospitals in 10 European countries, evidencing extreme variability of transfusion practice – not only between hospitals but also between Departments and also between physicians from one same Department. This evidences the need to unify transfusion criteria in order to minimize needless patient exposure to allogenic blood transfusions.22 In this scenario, PBMs appear with the purpose not of improving transfusion practice but of improving the patient clinical outcomes – though the optimization of transfusion practice is one of the many tools available to reach this objective. In our sample, many hospitals still have not implemented a PBM program; specifically, of the 111 hospitals in the study, 64.86% did not contemplate programs of this kind. Furthermore, 38.74% do not even have a transfusion protocol. On the other hand, the group of ICUs that exceed a transfusion rate of 20% in our study (representing 16.21% of the global ICUs) largely correspond to specialized polytrauma patient Units. As a result, specialized Units of this kind are those that conform a special group with large transfusion requirements, representing approximately 81% of the blood units, compared with the rest of the ICUs.23

However, variability is observed not only between hospitals. In our study we also evidenced differences in transfusion rates within one same hospital, specifically according to whether the patient meets criteria of anemia or not, or whether the patient constitutes a medical or a surgical case. This may be due to a range of factors, such as the training of physicians in this field in the Department of Intensive Care Medicine, but not to the number of residents in training, since the staff physician – alone or with the resident – is the professional that usually decides transfusion based on personal experience and the consensus recommendations. Residents in training make fewer than 2% of all transfusion decisions in Spain.23

A limitation of this study is the design involved, which is adequate for describing transfusion practices in this country and the variability between hospitals, though none of the patients were followed-up on beyond the 24-h duration of the study. Accordingly, the number of patients that died in the ICU was very low, and no evaluation was made of the duration of ICU stay. Likewise, the rest of patients were not monitored in order to thoroughly assess mortality associated to the transfused individuals. In turn, the study design did not contemplate the evaluation of adverse effects or reactions to blood transfusion. In this respect, we are conducting a new data compilation process covering a longer period, in order to conduct a follow-up of the ICU stay of patients with and without blood transfusion, with the purpose of analyzing the safety of the transfusion act in the real-life clinical setting.

Study conception and design: A. Robles and M. Quintana.

Data acquisition: M.A. Henríquez and García-Olmos.

Data analysis and interpretation: R. Juárez and S. Yus.

Drafting of the article: all the authors.

Final approval of the submitted manuscript version: all the authors.

The present study has received no financial support, and the authors declare that they have no conflicts of interest.