Cerebral microhemorrhages in children with congenital heart disease: Prevalence, risk factors, and impact on neurodevelopmental outcomes.

Background: Infants with complex congenital heart disease (CHD) require life-saving corrective/palliative heart surgery in the first weeks of life. These infants are at risk for brain injury and poor neurodevelopmental outcomes. Cerebral microhemorrhages (CMH) are frequently seen after neonatal bypass heart surgery, but it remains unknown if CMH are a benign finding or constitute injury. Herein, we investigate the risk factors for developing CMH and their clinical significance. Methods: 192 infants with CHD undergoing corrective cardiac surgery with cardiopulmonary bypass (CPB) at a single institution were prospectively evaluated with pre-(n = 183) and/or postoperative (n = 162) brain magnetic resonance imaging (MRI). CMH severity was scored based on total number of microhemorrhages. Antenatal, perioperative, and postoperative candidate risk factors for CMH and neurodevelopmental (ND) outcomes were analyzed. Eighteen-month neurodevelopmental outcomes were assessed using the Bayley-III Scales of Infants and Toddler Development in a subset of patients (n = 82). Linear regression was used to analyze associations between risk factors or ND outcomes and presence/number of CMH. Results: The most common CHD subtypes were hypoplastic left heart syndrome (HLHS) (37%) and transposition of the great arteries (TGA) (33%). Forty-two infants (23%) had CMH present on MRI before surgery and 137 infants (85%) post-surgery. No parameters evaluated were significant risk factors for preoperative CMH. In multivariate analysis, cardiopulmonary bypass (CPB) duration (p < 0.0001), use of extracorporeal membrane oxygenation (ECMO) support (p < 0.0005), postoperative seizure(s) (p < 0.03), and lower birth weight (p < 0.03) were associated with new or worsened CMH postoperatively. Higher CMH number was associated with lower scores on motor (p < 0.03) testing at 18 months. Conclusion: CMH is a common imaging finding in infants with CHD with increased prevalence and severity after CPB and adverse impact on neurodevelopmental outcomes starting at a young age. Longer duration of CPB and need for postoperative ECMO were the most significant risk factors for developing CMH. However, presence of CMH on preoperative scans indicates non-surgical risk factors that are yet to be identified. Neuroprotective strategies to mitigate risk factors for CMH may improve neurodevelopmental outcomes in this vulnerable population.

Diffuse Optical Monitoring of Cerebral Hemodynamics and Oxygen Metabolism during and after Cardiopulmonary Bypass: Hematocrit Correction and Neurological Vulnerability.

Cardiopulmonary bypass (CPB) provides cerebral oxygenation and blood flow (CBF) during neonatal congenital heart surgery, but the impacts of CPB on brain oxygen supply and metabolic demands are generally unknown. To elucidate this physiology, we used diffuse correlation spectroscopy and frequency-domain diffuse optical spectroscopy to continuously measure CBF, oxygen extraction fraction (OEF), and oxygen metabolism (CMRO2) in 27 neonatal swine before, during, and up to 24 h after CPB. Concurrently, we sampled cerebral microdialysis biomarkers of metabolic distress (lactate-pyruvate ratio) and injury (glycerol). We applied a novel theoretical approach to correct for hematocrit variation during optical quantification of CBF in vivo. Without correction, a mean (95% CI) +53% (42, 63) increase in hematocrit resulted in a physiologically improbable +58% (27, 90) increase in CMRO2 relative to baseline at CPB initiation; following correction, CMRO2 did not differ from baseline at this timepoint. After CPB initiation, OEF increased but CBF and CMRO2 decreased with CPB time; these temporal trends persisted for 0-8 h following CPB and coincided with a 48% (7, 90) elevation of glycerol. The temporal trends and glycerol elevation resolved by 8-24 h. The hematocrit correction improved quantification of cerebral physiologic trends that precede and coincide with neurological injury following CPB.

Effects of circulatory arrest and cardiopulmonary bypass on cerebral autoregulation in neonatal swine.

BACKGROUND: Cerebral autoregulation mechanisms help maintain adequate cerebral blood flow (CBF) despite changes in cerebral perfusion pressure. Impairment of cerebral autoregulation, during and after cardiopulmonary bypass (CPB), may increase risk of neurologic injury in neonates undergoing surgery. In this study, alterations of cerebral autoregulation were assessed in a neonatal swine model probing four perfusion strategies. METHODS: Neonatal swine (n = 25) were randomized to continuous deep hypothermic cardiopulmonary bypass (DH-CPB, n = 7), deep hypothermic circulatory arrest (DHCA, n = 7), selective cerebral perfusion (SCP, n = 7) at deep hypothermia, or normothermic cardiopulmonary bypass (control, n = 4). The correlation coefficient (LDx) between laser Doppler measurements of CBF and mean arterial blood pressure was computed at initiation and conclusion of CPB. Alterations in cerebral autoregulation were assessed by the change between initial and final LDx measurements. RESULTS: Cerebral autoregulation became more impaired (LDx increased) in piglets that underwent DH-CPB (initial LDx: median 0.15, IQR [0.03, 0.26]; final: 0.45, [0.27, 0.74]; p = 0.02). LDx was not altered in those undergoing DHCA (p > 0.99) or SCP (p = 0.13). These differences were not explained by other risk factors. CONCLUSIONS: In a validated swine model of cardiac surgery, DH-CPB had a significant effect on cerebral autoregulation, whereas DHCA and SCP did not. IMPACT: Approximately half of the patients who survive neonatal heart surgery with cardiopulmonary bypass (CPB) experience neurodevelopmental delays. This preclinical investigation takes steps to elucidate and isolate potential perioperative risk factors of neurologic injury, such as impairment of cerebral autoregulation, associated with cardiac surgical procedures involving CPB. We demonstrate a method to characterize cerebral autoregulation during CPB pump flow changes in a neonatal swine model of cardiac surgery. Cerebral autoregulation was not altered in piglets that underwent deep hypothermic circulatory arrest (DHCA) or selective cerebral perfusion (SCP), but it was altered in piglets that underwent deep hypothermic CBP.

Association of Pediatric ASPECTS and NIH Stroke Scale, Hemorrhagic Transformation, and 12-Month Outcome in Children With Acute Ischemic Stroke.

OBJECTIVE: We aimed to determine whether a modified pediatric Alberta Stroke Program Early CT Score (modASPECTS) is associated with clinical stroke severity, hemorrhagic transformation, and 12-month functional outcomes in children with acute AIS. METHODS: Children (29 days to <18 years) with acute AIS enrolled in two institutional prospective stroke registries at Children's Hospital of Philadelphia and Royal Children's Hospital Melbourne, Australia were retrospectively analyzed to determine whether modASPECTS, in which higher scores are worse, correlated with acute Pediatric NIH Stroke Scale (PedNIHSS) scores (children ≥2 years of age), was associated with hemorrhagic transformation on acute MRI, and correlated with 12-month functional outcome on the Pediatric Stroke Outcome Measure (PSOM). RESULTS: 131 children were included; 91 were ≥2 years of age. Median days from stroke to MRI was 1 (interquartile range [IQR] 0-1). Median modASPECTS was 4 (IQR 3-7). ModASPECTS correlated with PedNIHSS (rho=0.40, P=0.0001). ModASPECTS was associated with hemorrhagic transformation (OR 1.13 95% CI 1.02-1.25, P=0.018). Among children with follow-up (N=128, median 12.2 months, IQR 9.5-15.4 months), worse outcomes were associated with higher modASPECTS (common OR 1.14, 95%CI 1.04-1.24, P=0.005). The association between modASPECTS and outcome persisted when we adjusted for age at stroke ictus and the presence of tumor or meningitis as stroke risk factors (common OR 1.14, 95%CI 1.03-1.25, P=0.008). CONCLUSIONS: ModASPECTS correlates with PedNIHSS scores, hemorrhagic transformation, and 12-month functional outcome in children with acute AIS. Future pediatric studies should evaluate its usefulness in predicting symptomatic intracranial hemorrhage and outcome after acute revascularization therapies. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that the modified pediatric ASPECTS on MRI is associated with stroke severity (as measured by the baseline pediatric NIH Stroke Scale), hemorrhagic transformation, and 12-month outcome in children with acute supratentorial ischemic stroke.