In our study, TBSA, length of surgery, and Hb influenced the transfusion rate in burned children. Length of stay was not influenced by RBC transfusion. According to the German transfusion guidelines, more than half of the children were transfused too liberally.
Non-transfused children had a median area of 10% TBSA, whereas transfused children had a median area of 30% TBSA. A multicenter retrospective study in a mixed population of adults and children with burn injury found that 75% of patients with TBSA > 20% received blood transfusion . Another observational study evaluating predictive factors for blood transfusion in adults and children found TBSA > 20% is a useful predictor for blood transfusion . Only few data are available to evaluate the association between TBSA and transfusion in an exclusively pediatric collective study like ours. Interestingly, another retrospective study found in transfused children with burn injury a mean TBSA of 29 to 31%. This corresponds to our findings. Information of TBSA of non-transfused children were not evaluated in this study . Another retrospective cohort study evaluated the effects of a change to a restrictive blood transfusion protocol in acute pediatric burn injuries. Children who received blood had a mean TBSA of 45% (before the protocol change) and 43% (after the protocol change), respectively. TBSA of children who did not receive blood transfusion was not described .
In our study, the length of surgery also correlated with the transfusion rate. Obviously, this can be explained by the fact that surgeons need more time for larger TBSA.
Age did not influence transfusion rate. This statement contrasts the other finding that suggests younger age is a risk factor for transfusion. In an observational study examining transfusion practice in children older than 28 days who underwent surgery in different hospitals was found that younger age (29 days to 2 years) among other factors was a preoperative variable associated with increased odds of having an intraoperative or postoperative RBC transfusion . A recently published register study in pediatric patients undergoing complex cranial vault reconstruction identified that age less than 24 months as one of the factors for increased RBC transfusion .
Length of stay was mainly influenced by whether it was an emergency procedure, TSBA, and age, not by the transfusion rate. Prospective studies examining this subject in children are rare. Lacroix et al. compared in a prospective, multicenter study in stable, critically ill children in ICU restrictive with liberal RBC transfusion strategies and found no difference in length of stay in ICU . Retrospective studies in burned children with protocol changes showed that days of hospitalization were less  or the same  after the change. Prospective data investigating the impact of transfusion on length of total hospital stay in this special population are to the best of our knowledge not available.
In our study, transfusion had a measurable effect on heart rate and systolic blood pressure; however, the effect is small, thus we cannot exclude that this effect is due to other factors such as catecholamines.
Our study evaluated the minimal hemoglobin concentration of transfused and non-transfused children during their hospital stay. Lower hemoglobin concentration was associated with RBC transfusion. The median minimal hemoglobin concentration of non-transfused children was 10.7 g/dL, and 8 g/dL before receiving RBC. The German guidelines for blood transfusion recommend a threshold of 6 to 7 g/dL (hemodynamically stable) and 10 g/dL (hemodynamically unstable) for children older than 4 months with active bleeding . These guidelines do not specifically address children with burn injury, thus special Hb thresholds for this collective are not available in a guideline because available prospective randomized data of critically ill children without acute blood loss cannot be fully be applied to pediatric patients with burn injury  International guidelines propose lower guidelines for children with bleeding, but they do not specify Hb thresholds for unstable children because of insufficient data [13, 14]. 74% of the children were transfused too liberally. Most of the too liberal transfusions happened in children that did not receive catecholamines. The reason for this could be the threshold of 6 g/dL for stable children is a very restrictive approach that is not yet practiced. In a British multicenter observational study of RBC transfusion practice in children with a median age of 5 years, the median pre-transfusion hemoglobin was 7.9 g/dL . On the other hand, the small increase of Hb after transfusion in our study is a restrictive approach that corresponds to the recommendation that post-transfusion Hb should not be > 2 g/dl above the transfusion threshold . Unfortunately, database for risks or benefits of a restrictive transfusion approach versus a liberal one in pediatric patients is very small. One prospective landmark study of Lacroix et al. showed that restrictive transfusion strategy in stable critically ill children does not increase adverse events . A few clinical studies have examined blood transfusion effects retrospectively [28,29,30]. Similar to adults, they showed increased incidence of 30 days mortality, postoperative infections, and correlation between the volume of RBC transfused and the incidences of adverse outcomes , length of mechanical ventilation, and length of ICU stay [28, 29].
For the subgroup of children with burn injury a recent study showed that restrictive blood transfusion with a hemoglobin threshold of 7 g/dL protocol in acute pediatric burn care is safe, may reduce medical risks, and lower economic burden . Transfusion-related immunomodulation (TRIM) is one of the effects of allogeneic blood transfusion. To what extent these immunomodulatory effects alter clinical outcomes remains controversial . Children with burn injury are immunosuppressed, and massive transfusion could put them at risk for TRIM, transfusion-related graft-versus-host reaction and enhanced allograft survival. However, these effects are yet to be examined in pediatric population. Retrospective studies showed a potentially higher risk for the development of sepsis  In a prospective study among adults, wound healing, mortality and infection did not differ between restrictive and liberal transfused adult patients with burn injury .
Children with burn injury are immunosuppressed. Therefore, the risk of this complication should be minimized. In a retrospective cohort study, children with burn injury of 60% TBSA and concomitant inhalation injury were more likely to develop sepsis after transfusion of high amounts of blood products . Hence, children with burn injury could benefit from a restrictive transfusion practice in particular. Apart from that restrictive transfusion practice minimizes other adverse effect of transfusion in children like hyperkalemia , TACO, febrile hemolytic transfusion reactions and incorrect blood component use [11, 12]. Indeed, prospective studies in burned children examining the effects and safety of restrictive versus liberal regimen are lacking. In summary, the transfusion practice in the examined collective reflects that children are transfused more liberally than possible or recommended. In addition, PBM strategies helping to avoid transfusion were not (cell saver) or poorly (fibrinogen or tranexamic acid (TXA)) applied. Recommendations for the use of TXA, fibrinogen, and cell saver in pediatric patients have been made during the last 10 years [11, 13, 15, 32, 33]; however data whether these strategies are really practiced in pediatric perioperative transfusion practice is insufficient. Therefore, this study suggests a possible gap between recommendation and reality.