We read with great interest the article of Dieu et al.1  regarding cardiopulmonary bypass (CPB) priming strategy in pediatric cardiac surgery. In this double-blind randomized controlled study, the authors reported that priming with fresh frozen plasma or balanced crystalloids does not result in a different risk of postoperative bleeding and transfusion of allogeneic blood components. The authors clearly have to be congratulated for addressing a very relevant clinical question in a study with a high level of methodologic quality. However, several points need to be taken into account when interpreting the reported results.

First, the studied population is probably not at a high risk of postoperative bleeding requiring the transfusion of hemostatic agents such as fresh frozen plasma. Indeed, most patients enrolled in the trial were small children (above 1 yr of age) undergoing low- to moderate-risk surgery (Risk Adjustment for Congenital Heart Surgery score, 1 to 3), whereas neonates and infants with cyanotic disease have been shown to be especially at higher risk of significant postoperative blood loss.2  The results of the present study do not help to define the best CPB priming strategy in these high-risk populations.

Second, the authors decided to treat all the blood remaining in the circuit after CPB weaning with a cell saver, eliminating platelets and coagulation factors in the autologous blood retransfused to the patients. The use of cell salvage has been recommended to reduce perioperative transfusion.3  However, to our point of view, because one of the primary outcome of this study was postoperative bleeding, it would have been more rational to use ultrafiltration and/or modified ultrafiltration to reduce the positive fluid balance at the end of surgery, thus keeping coagulation factors in the autologous blood returned to the children. Also, the authors stated that the cell salvage blood at the end of the procedure could be administered when necessary: could it be that this autologous blood was discarded in some patients?

Third, there is some evidence that adding albumin to CPB priming could be beneficial for the patient in terms of perioperative fluid balance and weight gain. As demonstrated in several randomized controlled studies, 6% hydroxyethyl starch 130/0.4 could be a cost-effective alternative to albumin for CPB priming in pediatric cardiac surgery.4–6  Although we could agree that the evidence in favor of hydroxyethyl starch is not as high, there is also no clear evidence from the literature proving that a balanced crystalloid solution is effective and safe in this population.

Fourth, the authors advocated the double-blind design to justify the systematic transfusion of packed erythrocyte in the CPB prime. The author stated that the minimum desired hematocrit during CPB was 30% for patients with cyanotic heart disease and 25% for those with noncyanotic heart disease, which is not fully in line with actual transfusion guidelines in the field of pediatric patient blood management.3  Could it be that some patients received allogeneic blood in the CPB, although they should have achieved the desired hematocrit without transfusion? Also, the transfusion triggers used in the postoperative period are much higher than those actually recommended.3,7  To alleviate the problem regarding the maintenance of the double-blind design, the authors might have stratified the studied population according to the size of the CPB circuit, allowing study of a much broader population.

Because of these different elements, we think the study of Dieu et al.1  addresses the problem only partially, and further works are required to help clinicians in defining the best strategy to manage CPB priming in pediatric cardiac surgery.

Dr. Van Der Linden received, within the past 5 yr, fees for lectures and consultancies from Fresenius Kabi GmBH (Bad Homburg, Germany), Aguettan Medical SA (Lyon, France), and Vifor Pharma (Antwerpen, Belgium). The other authors declare no competing interests.

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