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Background: Cerebral autoregulation (CA) impairment is associated with neurological complications among children supported by extracorporeal membrane oxygenation (ECMO). Severe variations of arterial CO 2 (PaCO 2 ) and O 2 (PaO 2 ) tension after ECMO onset are common and associate with mortality and poor neurological outcome. The impact of gas exchange on CA among critically ill patients is poorly studied., Methods: Retrospective analysis of data collected prospectively from 30 children treated with veno-arterial or veno-venous ECMO in the PICU of Nantes University Hospital, France. A correlation coefficient between the variations of regional cerebral oxygen saturation (rSO 2 ) and the variations of mean arterial blood pressure (MAP) was calculated as an index of CA (cerebral oxygenation reactivity index, COx). Cox-MAP plots were investigated allowing determining lower limit of autoregulation (LLA) and upper limit of autoregulation (ULA) limits of autoregulation. Age-based normal blood pressure was used to adjust the MAP, LLA, and ULA data from each patient and then reported as percentage (nMAP, nLLA, and nULA, respectively). RSO 2 , COx, nMAP, nLLA, and nULA values were averaged over one hour before each arterial blood gas (ABG) sample during ECMO run., Results: Thirty children (median age 4.8 months [Interquartile range (IQR) 0.7-39.1], median weight 5 kg [IQR 4-15]) experiencing 31 ECMO runs were included in the study. Three hundred and ninety ABGs were analyzed. The highest values of COx were observed on day 1 (D1) of ECMO. The relationship between COx and PaCO 2 was nonlinear, but COx values tended to be lower in case of hypercapnia compared to normocapnia. During the whole ECMO run, a weak but significant correlation between PaCO 2 and nULA was observed (R = 0.432, p = 0.02). On D1 of ECMO, this correlation was stronger (R = 0.85, p = 0.03) and a positive correlation between nLLA and PaCO 2 was also found (R = 0.726, p < 0.001). A very weak negative correlation between PaO 2 and nULA was observed within the whole ECMO run and on D1 of ECMO (R =  -0.07 p = 0.04 and R =  -0.135 p =  <0.001, respectively). The difference between nULA and nLLA representing the span of the autoregulation plateau was positively correlated with PaCO 2 and negatively correlated with PaO 2 (R = 0.224, p = 0.01 and R =  -0.051, p = 0.004, respectively)., Conclusions: We observed a complex relationship between PaCO 2 and CA, influenced by the level of blood pressure. Hypercapnia seems to be globally protective in normotensive or hypertensive condition, while, in case of very low MAP, hypercapnia may disturb CA as it increases LLA. These data add additional arguments for very cautiously lower PaCO 2 , especially after ECMO start., (© 2021. Springer Science+Business Media, LLC, part of Springer Nature and Neurocritical Care Society.)

Objective: Cerebral autoregulation (CA) impairment may pose a risk factor for neurological complications among children supported by extracorporeal membrane oxygenation (ECMO). Our first objective was to investigate the feasibility of CA continuous monitoring during ECMO treatment and to describe its evolution over time. The second objective was to analyze the association between CA impairment and neurological outcome., Design: Observational prospective study., Patients and Setting: Twenty-nine children treated with veno-arterial or veno-venous ECMO in the PICU of Nantes University Hospital, France, and the PICU of the IRCCS Giannina Gaslini Institute in Genoa, Italy., Measurements: A correlation coefficient between the variations of regional cerebral oxygen saturation and the variations of mean arterial blood pressure (MAP) was calculated as an index of CA (cerebral oxygenation reactivity index, COx). A COx > 0.3 was considered as indicative of autoregulation impairment. COx-MAP plots were investigated allowing determining optimal MAP (MAPopt) and limits of autoregulation: lower (LLA) and upper (ULA). Neurological outcome was assessed by the onset of an acute neurological event (ANE) after ECMO start., Results: We included 29 children (median age 84 days, weight 4.8 kg). MAPopt, LLA, and ULA were detected in 90.8% (84.3-93.3) of monitoring time. Mean COx was significantly higher during day 1 of ECMO compared to day 2 [0.1 (0.02-0.15) vs. 0.01 (- 0.05 to 0.1), p = 0.002]. Twelve children experienced ANE (34.5%). The mean COx and the percentage of time spent with a COx > 0.3 were significantly higher among ANE+ compared to ANE- patients [0.09 (0.01-0.23) vs. 0.04 (- 0.02 to 0.06), p = 0.04 and 33.3% (24.8-62.1) vs. 20.8% (17.3-23.7) p = 0.001]. ANE+ patients spent significantly more time with MAP below LLA [17.2% (6.5-32.9) vs. 5.6% (3.6-9.9), p = 0.02] and above ULA [13% (5.3-38.4) vs. 4.2% (2.7-7.4), p = 0.004], respectively., Conclusion: CA assessment is feasible in pediatric ECMO. The first 24 h following ECMO represents the most critical period regarding CA. Impaired autoregulation is significantly more severe among patients who experience ANE.