LAUSR

To the Editor: We read with great interest the article published in the recent issue of Pediatric Critical Care Medicine by Oberender et al (1) evaluating the use of venoarterial extracorporeal membrane oxygenation (ECMO) versus conventional medical therapy for the management of pediatric refractory septic shock (RSS). This retrospective study included 164 patients from seven international experienced centers; among these, 44 were supported with ECMO and reported a survival to hospital discharge of 50%. Even though these outcome results did not reach a statistical significance, the authors showed a 10% increase in the survival to hospital discharge in the venoarterial ECMO cohort compared with the conventional therapy cohort. These results are encouraging, although they require further investigations. In fact, this and previous studies (1, 2) aiming at evaluate the role of venoarterial ECMO in pediatric septic shock presented three important limits: the lack of a standardized definition of RSS, the lack of standardized criteria for starting venoarterial ECMO, and the lack of an accurate hemodynamic classification of RSS (1–3). Actually, the indications for the use of venoarterial ECMO in children with septic shock are related to cardiocirculatory failure with cardiac arrest or RSS (4). Recently, RSS in children was defined (3) and its definition demonstrated to have a very high accuracy in identifying the most severe patients. The use of this classification to early identify RSS associated to standardized criteria for starting venoarterial ECMO as well as the use of an advanced hemodynamic monitoring to classify the type of septic shock (5) would probably reduce the initiation bias linked to centers, physicians, and patients’ clinical conditions. We strongly believe that the rationale for venoarterial ECMO support in septic shock is the “early” treatment of patients with high risk of mortality such as the ones with RSS. This aspect was already addressed by MacLaren et al (2) showing that the best predictor of ECMO survival in children with septic shock was a low pre-ECMO arterial lactate value and recently confirmed by Lasa et al (6) and Oberender et al (1) showing that venoarterial ECMO improved survival in septic patients with cardiac arrest. The use of an advanced hemodynamic monitoring in patients with RSS would allow to “accurately” differentiate a low cardiac output state associated to high systemic vascular resistance from a low cardiac output state associated to low systemic vascular resistance or a high cardiac output state associated to low systemic vascular resistance states. This hemodynamic data would impact treatment options and consequently outcomes. We retain that the “only” use of the Vasoactive-Inotropic Score (VIS), is of limited value since VIS can provide the “same” value for different hemodynamic states according to the level of drugs used. Furthermore, we also believe that in presence of an advanced hemodynamic monitoring, the comparison between “high ECMO flows” versus “low ECMO flow” looses sense because we can have continuously monitored at bedside both cardiac output and systemic vascular resistance and thus evaluate if “high ECMO flows” are needed or not. So what’s next to move forward with venoarterial ECMO in RSS? It is urgently needed to evaluate European Society of Pediatric and Neonatal Intensive Care-RSS criteria and its dynamics in the course preceding mechanical support initiation. This is not only a prerequirement for any controlled study evaluating venoarterial ECMO in pediatric septic shock, but also to standardize patients analysis in retrospective studies. The authors have disclosed that they do not have any potential conflicts of interest.