MRI, MRA, and neurodevelopmental outcome following neonatal ECMO

Veno-arterial extracorporeal membrane oxygenation for respiratory and cardiac support in neonates: a single center experience

Objective

Extracorporeal membrane oxygenation (ECMO) is an advanced life support that has been utilized in the neonate for refractory respiratory and circulatory failure. Striving for the best outcomes and understanding optimal surgical techniques continue to be at the forefront of discussion and research. This study presents a single-center experience of cervically cannulated neonatal patients on V-A ECMO, a description of our cannulation/decannulation techniques and our patient outcomes.

Methods

Single center retrospective review of neonates who received neck V-A ECMO support from January 2012 to December 2022. The data and outcomes of the patients were retrospectively analyzed.

Results

A total of 78 neonates received V-A ECMO support. There were 66 patients that received ECMO for respiratory support, the other 12 patients that received ECMO for cardiac support. The median duration of ECMO support was 109 (32-293) hours for all patients. During ECMO support, 20 patients died and 5 patients discontinued treatment due to poor outcome or the cost. A total of 53 (68%) patients were successfully weaned from ECMO, but 3 of them died in the subsequent treatment. Overall 50 (64%) patients survived to hospital discharge. In this study, 48 patients were cannulated using the vessel sparing technique, the other 30 patients were cannulated using the ligation technique. We found no significant difference in the rates of normal cranial MRI at discharge between survivors with and without common carotid artery ligation.

Conclusion

We achieved satisfactory outcomes of neonatal ECMO in 11-year experience. This study found no significant difference in early neuroimaging between survivors with and without common carotid artery ligation. The long-term neurological function of ECMO survivors warranted further follow-up and study.

Retrospective analysis of neurological findings in esophageal atresia: Allostatic load of disease complexity, cumulative sedation, and anesthesia exposure

BACKGROUND

There is limited knowledge regarding the impact of perioperative critical care on frequency of neurological imaging findings following esophageal atresia (EA) repair.

METHODS

This is a retrospective study of infants (n = 70) following EA repair at a single institution (2009-2020). Sex, gestational age at birth, type of surgical repair, underlying disease severity, and frequency of neurologic imaging findings were obtained. We quantified the length of postoperative pain/sedation treatment and anesthesia exposure in the first year of life. Data were presented as numerical sums and percentages, while associations were measured using Spearman's Rho.

RESULTS

Vertebral/spinal cord imaging was performed in all infants revealing abnormalities in 44% (31/70). Cranial/brain imaging findings were identified in 67% (22/33) of infants in the context of clinically indicated imaging (47%; 33/70). Long-gap EA patients (n = 16) received 10 times longer postoperative pain/sedation treatment and twice the anesthesia exposure compared with short-gap EA patients (n = 54). The frequency of neurologic imaging findings did not correlate with underlying disease severity scores, length of pain/sedation treatment, or cumulative anesthesia exposure. Lack of associations between clinical measures and imaging findings should be interpreted with caution given possible underestimation of cranial/brain findings.

CONCLUSIONS

We propose that all infants with EA undergo brain imaging in addition to routine spinal imaging given the high burden of abnormal brain/cranial findings in our cohort. Quantification of pain/sedation and anesthesia exposure in long-gap EA patients could be used as indirect markers in future studies assessing the risk of neurological sequelae as evidenced by early abnormalities on brain imaging.

A Systematic Review of Clinical Outcomes After Carotid Artery Ligation Versus Carotid Artery Reconstruction Following Venoarterial Extracorporeal Membrane Oxygenation in Infants and Children

INTRODUCTION

In pediatric and neonatal populations, the carotid artery is commonly cannulated for venoarterial (VA) extracorporeal membrane oxygenation (ECMO). The decision to ligate (carotid artery ligation [CAL]) versus reconstruct (carotid artery reconstruction [CAR]) the artery at decannulation remains controversial as long-term neurologic outcomes remain unknown. The objective of this study was to summarize current literature on clinical outcomes following CAL and CAR after Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO).

METHODS

PubMed (MEDLINE), Embase, Web of Science, and Cochrane databases were searched using keywords from January 1950 to October 2020. Studies examining clinical outcomes following CAL and CAR for VA-ECMO in patients <18 y of age were included. Prospective and retrospective cohort studies, case series, case-control studies, and case reports were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were performed independently by two reviewers. Assessment of risk of bias was performed.

RESULTS

Eighty studies were included and classified into four categories: noncomparative clinical outcomes after CAL (n = 23, 28.8%), noncomparative clinical outcomes after CAR (n = 12, 15.0%), comparative clinical outcomes after CAL and/or CAR (n = 28, 35.0%), and case reports of clinical outcomes after CAL and/or CAR (n = 17, 21.3%). Follow-up ranged from 0 to 11 y. CAR patency rates ranged from 44 to 100%. There was no substantial evidence supporting an association between CAL versus CAR and short-term neurologic outcomes.

CONCLUSIONS

Studies evaluating outcomes after CAL versus CAR for VA-ECMO are heterogeneous with limited generalizability. Further studies are needed to evaluate long-term consequences of CAL versus CAR, especially as the first survivors of pediatric/neonatal ECMO approach an age of increased risk of carotid stenosis and stroke.

Blood-brain barrier dysfunction in intensive care unit

The central nervous system is characterized by a peculiar vascularization termed blood-brain barrier (BBB), which regulates the exchange of cells and molecules between the cerebral tissue and the whole body. BBB dysfunction is a life-threatening condition since its presence corresponds to a marker of severity in most diseases encountered in the intensive care unit (ICU). During critical illness, inflammatory response, cytokine release, and other phenomena activating the brain endothelium contribute to alterations in the BBB and increase its permeability to solutes, cells, nutrients, and xenobiotics. Moreover, patients in the ICU are often old, with underlying acute or chronic diseases, and overly medicated due to their critical condition; these factors could also contribute to the development of BBB dysfunction. An accurate diagnostic approach is critical for the identification of the mechanisms underlying BBB alterations, which should be rapidly managed by intensivists. Several methods were developed to investigate the BBB and assess its permeability. Nevertheless, in humans, exploration of the BBB requires the use of indirect methods. Imaging and biochemical methods can be used to study the abnormal passage of molecules through the BBB. In this review, we describe the structural and functional characteristics of the BBB, present tools and methods for probing this interface, and provide examples of the main diseases managed in the ICU that are related to BBB dysfunction.

An ode to fetal, infant, and toddler neuroimaging: Chronicling early clinical to research applications with MRI, and an introduction to an academic society connecting the field

Fetal, infant, and toddler neuroimaging is commonly thought of as a development of modern times (last two decades). Yet, this field mobilized shortly after the discovery and implementation of MRI technology. Here, we provide a review of the parallel advancements in the fields of fetal, infant, and toddler neuroimaging, noting the shifts from clinical to research use, and the ongoing challenges in this fast-growing field. We chronicle the pioneering science of fetal, infant, and toddler neuroimaging, highlighting the early studies that set the stage for modern advances in imaging during this developmental period, and the large-scale multi-site efforts which ultimately led to the explosion of interest in the field today. Lastly, we consider the growing pains of the community and the need for an academic society that bridges expertise in developmental neuroscience, clinical science, as well as computational and biomedical engineering, to ensure special consideration of the vulnerable mother-offspring dyad (especially during pregnancy), data quality, and image processing tools that are created, rather than adapted, for the young brain.

ECMO in neonates: The association between cerebral hemodynamics with neurological function

Extracorporeal membrane oxygenation (ECMO) is a superior life support technology, commonly employed in critical patients with severe respiratory or hemodynamic failure to provide effective respiratory and circulatory support, which is especially recommended for the treatment of critical neonates. However, the vascular management of neonates with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is still under controversy. Reconstruction or ligation for the right common carotid artery (RCCA) after ECMO is inconclusive. This review summarized the existed studies on hemodynamics and neurological function after vascular ligation or reconstruction hoping to provide better strategies for vessel management in newborns after ECMO. After reconstruction, the right cerebral blood flow can increase immediately, and the normal blood supply can be restored rapidly. But the reconstructed vessel may be occluded and stenotic in long-term follow-ups. Ligation may cause lateralization damage, but there could be no significant effect owing to the establishment of collateral circulation. The completion of the circle of Willis, the congenital anomalies of cerebral or cervical vasculature, the duration of ECMO, and the vascular condition at the site of arterial catheterization should be assessed carefully before making the decision. It is also necessary to follow up on the reconstructed vessel sustainability, and the association between cerebral hemodynamics and neurological function requires further large-scale multi-center studies.

Decreased Brain Volumes and Infants With Congenital Heart Disease Undergoing Venoarterial Extracorporeal Membrane Oxygenation

OBJECTIVES

The aims of this study were to: i) determine the spectrum of brain injury and ii) compare brain volumes between pre- and postoperative brain MRI in the infants receiving extracorporeal membrane oxygenation compared with those who did not require extracorporeal membrane oxygenation.

DESIGN

Cohort study of infants with D-transposition of the great arteries or single ventricle physiology. Brain volume (cm) was measured using a segmentation of a volumetric T1-weighted gradient echo sequence. Brain imaging findings (intraventricular hemorrhage, white matter injuries, and stroke) were analyzed with respect to known clinical risk factors for brain injury and adverse neurodevelopmental outcomes. Clinical factors were collected by retrospective chart review. The association between brain volume and extracorporeal membrane oxygenation was evaluated using generalized estimating equations to account for repeated measures.

SETTING

Prospective and single-centered study.

PATIENTS

One hundred nine infants (median gestational age, 39.1 wk) with D-transposition of the great arteries (n = 77) or single ventricle physiology (n = 32) were studied pre- and postoperatively with MRI as per clinical protocol.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 28 infants (26%) receiving extracorporeal membrane oxygenation, 19 (68%) were supported with extracorporeal membrane oxygenation once, and nine (32%) were supported 2-4 times. On postoperative MRI, new white matter injury was found in only five (17%) of the extracorporeal membrane oxygenation infants versus 40 (49%) in the non-extracorporeal membrane oxygenation group (p = 0.073). The rate of stroke (9% vs 10%), intraventricular hemorrhage (24% vs 29%), and hypoxic ischemia (3% vs 14%) did not differ between the non-extracorporeal membrane oxygenation and extracorporeal membrane oxygenation groups (all p > 0.5). Accounting for D-transposition of the great arteries or single ventricle physiology diagnosis, infants requiring extracorporeal membrane oxygenation had slower brain volume with single (β = -1.67) or multiple extracorporeal membrane oxygenation runs ([β = -6.54]; overall interaction p = 0.012).

CONCLUSIONS

Patients with d-transposition of the great arteries or single ventricle physiology undergoing extracorporeal membrane oxygenation at our center have a similar incidence of brain injury but more significant impairment of perioperative brain volumes than those not requiring extracorporeal membrane oxygenation.

EEG features of brain injury during extracorporeal membrane oxygenation in children

OBJECTIVE

To examine EEG features of major pathophysiology in children undergoing extracorporeal membrane oxygenation (ECMO).

METHODS

This was a single-center, retrospective study of 201 pediatric patients on ECMO, using the first 24 hours of continuous EEG (cEEG) monitoring, collating background activity and electrographic seizures (ES) with imaging, ECMO type, and outcome.

RESULTS

Severely abnormal cEEG background occurred in 12% (25/201), and was associated with death (sensitivity 0.23, specificity 0.97). ES occurred in 16% (33/201) within 3.2 (0.6-20.3) hours (median [interquartile range]) of cEEG commencement, and higher ES burden was associated with death. ES was always associated with ipsilateral injury (p = 0.006), but occurred in only one-third of cases with abnormal imaging. In 28 patients with isolated hemisphere lesion, type of arterial ECMO cannulation was associated with side of injury: right carotid cannulation was associated with right hemisphere lesions, and ascending aorta cannulation with left hemisphere lesions (odds ratio, 0.29 [95% confidence interval, 0.08-0.98], p = 0.03).

CONCLUSIONS

After starting ECMO, cEEG background activity has the potential to inform prognosis. Type of arterial (carotid vs aortic) ECMO correlates with side of focal cerebral injury, which in ≈33% is associated with presence of ES. We hypothesize that the differential distribution reflects abnormal flow dynamics or embolic injury.

Imaging of cerebral complications of extracorporeal membrane oxygenation in infants with congenital heart disease - ultrasound with multimodality correlation

Cranial ultrasound on neonatal intensive care units is generally performed by intensive care physicians, but radiologists often provide this crucial bedside test to children on specialist paediatric cardiac intensive care units. On a paediatric cardiac intensive care unit, complex congenital cardiac conditions are commonly encountered in both pre- and postoperative scenarios, often with the use of extracorporeal membrane oxygenation (ECMO), which both increases the risks of a number of neurologic complications and results in significant changes in vascular physiology. The aim of this pictorial essay is to discuss cranial ultrasound technique, demonstrate the changes in Doppler flow profiles resulting from veno-arterial extracorporeal membrane oxygenation and congenital cardiac conditions, and illustrate commonly encountered intracranial complications of extracorporeal membrane oxygenation support in congenital cardiac care.

Neurologic Injury and Brain Growth in the Setting of Long-Gap Esophageal Atresia Perioperative Critical Care: A Pilot Study

We previously showed that infants born with long-gap esophageal atresia (LGEA) demonstrate clinically significant brain MRI findings following repair with the Foker process. The current pilot study sought to identify any pre-existing (PRE-Foker process) signs of brain injury and to characterize brain and corpus callosum (CC) growth. Preterm and full-term infants (n = 3/group) underwent non-sedated brain MRI twice: before (PRE-Foker scan) and after (POST-Foker scan) completion of perioperative care. A neuroradiologist reported on qualitative brain findings. The research team quantified intracranial space, brain, cerebrospinal fluid (CSF), and CC volumes. We report novel qualitative brain findings in preterm and full-term infants born with LGEA before undergoing Foker process. Patients had a unique hospital course, as assessed by secondary clinical end-point measures. Despite increased total body weight and absolute intracranial and brain volumes (cm3) between scans, normalized brain volume was decreased in 5/6 patients, implying delayed brain growth. This was accompanied by both an absolute and relative CSF volume increase. In addition to qualitative findings of CC abnormalities in 3/6 infants, normative CC size (% brain volume) was consistently smaller in all infants, suggesting delayed or abnormal CC maturation. A future larger study group is warranted to determine the impact on the neurodevelopmental outcomes of infants born with LGEA.

Infant Brain Structural MRI Analysis in the Context of Thoracic Non-cardiac Surgery and Critical Care

Objective: To determine brain magnetic resonance imaging (MRI) measures of cerebrospinal fluid (CSF) and whole brain volume of full-term and premature infants following surgical treatment for thoracic non-cardiac congenital anomalies requiring critical care. Methods: Full-term (n = 13) and pre-term (n = 13) patients with long-gap esophageal atresia, and full-term naïve controls (n = 19) < 1 year corrected age, underwent non-sedated brain MRI following completion of thoracic non-cardiac surgery and critical care treatment. Qualitative MRI findings were reviewed and reported by a pediatric neuroradiologist and neurologist. Several linear brain metrics were measured using structural T1-weighted images, while T2-weighted images were required for segmentation of total CSF and whole brain tissue using the Morphologically Adaptive Neonatal Tissue Segmentation (MANTiS) tool. Group differences in absolute (mm, cm³) and normalized (%) data were analyzed using a univariate general linear model with age at scan as a covariate. Mean normalized values were assessed using one-way ANOVA. Results: Qualitative brain findings suggest brain atrophy in both full-term and pre-term patients. Both linear and volumetric MRI analyses confirmed significantly greater total CSF and extra-axial space, and decreased whole brain size in both full-term and pre-term patients compared to naïve controls. Although linear analysis suggests greater ventricular volumes in all patients, volumetric analysis showed that normalized ventricular volumes were higher only in premature patients compared to controls. Discussion: Linear brain metrics paralleled volumetric MRI analysis of total CSF and extra-axial space, but not ventricular size. Full-term infants appear to demonstrate similar brain vulnerability in the context of life-saving thoracic non-cardiac surgery requiring critical care as premature infants.

Neuroimaging for Neurodevelopmental Prognostication in High-Risk Neonates

Predicting neurodevelopmental outcomes in high-risk neonates remains challenging despite advances in neonatal care. Early and accurate characterization of infants at risk for neurodevelopmental delays is necessary to best identify those who may benefit from existing early interventions and novel therapies that become available. Although neuroimaging is a promising biomarker in the prediction of neurodevelopmental outcomes in high-risk infants, it requires additional resources and expertise. Despite many advances in neonatal neuroimaging, there remain limitations in relating early neuroimaging findings with long-term outcomes; further studies are necessary to determine the optimal protocols to best identify high-risk patients and improve neurodevelopmental outcome prediction.

Cerebral Perfusion After Repair of Congenital Diaphragmatic Hernia with Common Carotid Artery Occlusion After ECMO Therapy

AIM

To prospectively evaluate cerebral perfusion after repair of congenital diaphragmatic hernia (CDH) and right-common-carotid-artery (rCCA) occlusion after extracorporeal membrane oxygenation (ECMO) therapy.

PATIENTS AND METHODS

A total of 29 2-year-old-children with a history of CDH repair underwent cerebral magnetic resonance perfusion imaging. In 14 patients, the rCCA was occluded after ECMO therapy. Fifteen patients with CDH without ECMO served as controls. Regional cerebral-blood-flow (rCBF) was measured cortically and subcortically in both hemispheres and compared intra-individually and between both groups.

RESULTS

Patients with rCCA-occlusion showed intra-individual side differences between hemispheres, with significantly lower subcortical perfusion of the right hemisphere and reduced cortical perfusion. In one-third of patients with rCCA-occlusion, rCBF of the right-hemisphere was reduced by more than 20% when compared to the left hemisphere. Despite intra-individual side differences, mean rCBF in patients with rCCA occlusion was not reduced compared to controls.

CONCLUSION

Beside intra-individual side differences, overall right hemisphere perfusion is sufficient after rCCA-occlusion due to collateral blood supply.

Neuromonitoring in the neonatal ECMO patient

Utilization of extraocorporeal membrane oxygenation (ECMO) has become increasingly widespread as a bridging therapy for neonates with severe, reversible respiratory or cardiac diseases. While significant risks remain, due to advances in medical and surgical management, overall mortality has decreased. However, short and long-term neurological morbidity has remained high. Therefore, increasing attention has been focused on multimodal neuromonitoring to track and optimally, minimize or prevent intracranial injury. This review will explore the the indications, advantages, disadvantages, timing, frequency, duration, and any known correlation with neurodevelopmental outcomes of common types of neuromonitoring in the neonatal ECMO population. Investigational monitoring techniques such as NIRS will be briefly reviewed.

Improving Long-Term Outcomes After Extracorporeal Membrane Oxygenation: From Observational Follow-Up Programs Toward Risk Stratification

Since the introduction of extracorporeal membrane oxygenation (ECMO), more neonates and children with cardiorespiratory failure survive. Interest has therefore shifted from reduction of mortality toward evaluation of long-term outcomes and prevention of morbidity. This review addresses the changes in ECMO population and the ECMO-treatment that may affect long-term outcomes, the diagnostic modalities to evaluate neurological morbidities and their contributions to prognostication of long-term outcomes. Most follow-up data have only become available from observational follow-up programs in neonatal ECMO-survivors. The main topics are discussed in this review. Recommendations for long-term follow up depend on the presence of neurological comorbidity, the nature and extent of the underlying disease, and the indication for ECMO. Follow up should preferably be offered as standard of care, and in an interdisciplinary, structured and standardized way. This permits evaluation of outcome data and effect of interventions. We propose a standardized approach and recommend that multiple domains should be evaluated during long-term follow up of neonates and children who needed extracorporeal life support.

Patterns of Head Computed Tomography Abnormalities During Pediatric Extracorporeal Membrane Oxygenation and Association With Outcomes

BACKGROUND

We sought to classify type and distribution of acute infarction and hemorrhage on head computed tomography (CT) during pediatric extracorporeal membrane oxygenation (ECMO). We also analyzed the occurrence of seizures on electroencephalography and outcomes between those with and without CT abnormalities.

METHODS

We conducted a single center observational study in pediatric intensive care units. The medical records of 179 children who underwent ECMO between 2009 and 2013 were reviewed. No interventions were done.

RESULTS

A total of 46% (82/179) of children underwent CT. Of these, 60% (49/82) had acute pathology. Cerebral infarction occurred in 55% (27/49) and hemorrhage in 41% (20/49). Infarction was arterial in 67% (18/27) with a preponderance in the middle cerebral artery territory (17 patients). Infarction was bilateral in 41% (11/27) and not specific to the side of cannulation in the rest. Sensitivity and specificity for head ultrasound in predicting infarction on CT were 100% and 53%, respectively. A total of 36% (65/179) underwent continuous encephalography monitoring; 22% (14/65) of these had electrographic seizures. Electrographic seizures were increased in those with infarction (odds ratio [OR], 6.81; 95% confidence interval [CI], 1.98 to 23.43). Survival was reduced with both infarction (OR, 0.22; 95% CI, 0.09 to 0.54) and hemorrhage (OR, 0.31; 95% CI, 0.13 to 0.72). Children with CT abnormalities had more unfavorable outcomes (P = 0.01).

CONCLUSIONS

Head ultrasound is insufficient to rule out infarction. Infarction is middle cerebral artery predominant and associated with an increased risk of electrographic seizures.

Transcranial Doppler Identification of Neurologic Injury during Pediatric Extracorporeal Membrane Oxygenation Therapy

BACKGROUND

We used transcranial Doppler to examine changes in cerebral blood flow velocity in children treated with extracorporeal membrane oxygenation. We examined the association between those changes and radiologic, electroencephalographic, and clinical evidence of neurologic injury.

METHODS

This was a retrospective review and prospective observational study of patients 18 years old and younger at a single university children's hospital. Transcranial Doppler studies were obtained every other day during the first 7 days of extracorporeal membrane oxygenation, and 1 additional study following decannulation, in conjunction with serial neurologic examinations, brain imaging, and 6- to 12-month follow-up.

RESULTS

The study included 27 patients, the majority (26) receiving veno-arterial extracorporeal membrane oxygenation. Transcranial Doppler velocities during extracorporeal membrane oxygenation were significantly lower than published values for age-matched healthy and critically ill children across different cerebral arteries. Neonates younger than 10 days had higher velocities than expected. Blood flow velocity increased after extracorporeal membrane oxygenation decannulation and was comparable with age-matched critically ill children. There was no significant association between velocity measurements of individual arteries and acute neurologic injury as defined by either abnormal neurologic examination, seizures during admission, or poor pediatric cerebral performance category. However, case analysis identified several patients with regional and global increases in velocities that corresponded to neurologic injury including stroke and seizures.

CONCLUSIONS

Cerebral blood flow velocities during extracorporeal membrane oxygenation deviate from age-specific normal values in all major cerebral vessels and across different age groups. Global or regional elevations and asymmetries in flow velocity may suggest impending neurologic injury.

Patterns of Brain Injury in Newborns Treated with Extracorporeal Membrane Oxygenation

BACKGROUND AND PURPOSE

Neonates treated with extracorporeal membrane oxygenation are at risk for brain injury and subsequent neurodevelopmental compromise. Advances in MR imaging and improved accessibility have led to the increased use of routine MR imaging after extracorporeal membrane oxygenation. Our objective was to describe the frequency and patterns of extracorporeal membrane oxygenation-related brain injury based on MR imaging findings in a large contemporary cohort of neonates treated with extracorporeal membrane oxygenation.

MATERIALS AND METHODS

This was a retrospective study of neonatal patients treated with extracorporeal membrane oxygenation from 2005-2015 who underwent MR imaging before discharge. MR imaging and ultrasound studies were reviewed for location and type of parenchymal injury, ventricular abnormalities, and increased subarachnoid spaces. Parenchymal injury frequencies between patients treated with venoarterial and venovenous extracorporeal membrane oxygenation were compared by χ² tests.

RESULTS

Of 81 neonates studied, 46% demonstrated parenchymal injury; 6% showed infarction, mostly in vascular territories (5% anterior cerebral artery, 5% MCA, 1% posterior cerebral artery); and 20% had hemorrhagic lesions. The highest frequency of injury occurred in the frontal (right, 24%; left, 25%) and temporoparietal (right, 14%; left, 19%) white matter. Sonography had low sensitivity for these lesions. Other MR imaging findings included volume loss (35%), increased subarachnoid spaces (44%), and ventriculomegaly (17% mild, 5% moderate, 1% severe). There were more parenchymal injuries in neonates treated with venoarterial (49%) versus venovenous extracorporeal membrane oxygenation (29%, P = .13), but the pattern of injury was consistent between both modes.

CONCLUSIONS

MR imaging identifies brain injury in nearly half of neonates after treatment with extracorporeal membrane oxygenation. The frontal and temporoparietal white matter are most commonly affected, without statistically significant laterality. This pattern of injury is similar between venovenous and venoarterial extracorporeal membrane oxygenation, though the frequency of injury may be higher after venoarterial extracorporeal membrane oxygenation.

MRI for neurodevelopmental prognostication in the high-risk term infant

MRI performed in the neonatal period has become a tool widely used by clinicians and researchers to evaluate the developing brain. MRI can provide detailed anatomical resolution, enabling identification of brain injuries due to various perinatal insults. This review will focus on the link between neonatal MRI findings and later neurodevelopmental outcomes in high-risk term infants. In particular, the role of conventional and advanced MR imaging in prognosticating outcomes in neonates with hypoxic-ischemic encephalopathy, ischemic perinatal stroke, need for extracorporeal membrane oxygenation life support, congenital heart disease, and other neonatal neurological conditions will be discussed.

ECMO in neonates: neuroimaging findings and outcome

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for newborns with severe but reversible respiratory failure. Although ECMO has significantly improved survival, it is associated with substantial complications, of which intracranial injuries are the most important. These injuries consist of hemorrhagic and non-hemorrhagic, ischemic lesions. Different from the classical presentation of hemorrhages in preterm infants, hemorrhages in ECMO-treated newborns are mainly parenchymal and with a high percentage in the posterior fossa area. There are conflicting data on the predominant occurrence of cerebral lesions in the right hemisphere. The existence of intracerebral injuries and the classification of its severity are the major predictors of neurodevelopmental outcome. This section will discuss the known data on intracranial injury in the ECMO population and the effect of ECMO on the brain.

Brain injury associated with neonatal extracorporeal membrane oxygenation in the Netherlands: a nationwide evaluation spanning two decades

OBJECTIVE

To determine the prevalence of and to classify ultrasound-proven brain injury during neonatal extracorporeal membrane oxygenation in The Netherlands.

DESIGN

Retrospective nationwide study (Rotterdam and Nijmegen), spanning two decades.

SETTING

Level III university hospitals.

SUBJECTS

All neonates who underwent neonatal extracorporeal membrane oxygenation from 1989 to 2010.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cranial ultrasound images were reviewed independently by two investigators without knowledge of primary diagnosis, outcome, type of extracorporeal membrane oxygenation, or statistics. The scans were reviewed for lesion type and timing, with the use of a refined classification method for focal brain injury. Extracorporeal membrane oxygenation type was venoarterial in 88%. Brain abnormalities were detected in 17.3%: primary hemorrhage was most frequent (8.8%). Stroke was identified in 5% of the total group, with a notable significant preference for the left hemisphere (in 70%). Lobar hematoma (prevalence 2.2 %) was also significantly left predominant.

CONCLUSION

The incidence of brain injury found with cranial ultrasound in The Netherlands of the patients treated with extracorporeal membrane oxygenation during the neonatal period was 17.3%. Primary hemorrhage was the largest group of lesions, not clearly side-specific except for lobar bleeding, most probably related to changes in venous flow. Arterial ischemic stroke occurred predominant in the left hemisphere.

Outcomes following extracorporeal membrane oxygenation in children with cardiac disease

Extracorporeal membrane oxygenation is a commonly used form of mechanical circulatory support in children with congenital or acquired heart disease and cardiac failure refractory to conventional medical therapies. In children with heart disease who suffer cardiac arrest, extracorporeal membrane oxygenation has been successfully used to provide cardiopulmonary support when conventional resuscitation has failed to establish return of spontaneous circulation. Survival to hospital discharge for children with heart disease support is approximately 40% but varies widely based on age, indication for support, and underlying cardiac disease. Although extracorporeal membrane oxygenation is lifesaving in many instances, it is associated with many complications and is expensive. Thus, a clear understanding of survival to discharge and long-term functional and neurologic outcomes are essential to guide the use of extracorporeal membrane oxygenation now and in the future. This review, part of the Pediatric Cardiac Intensive Care Society/Extracorporeal Life Support Organization Joint Statement on Mechanical Circulatory Support, summarizes current knowledge on short- and long-term outcomes for extracorporeal membrane oxygenation used to support children with cardiac disease.

Cerebral aspects of neonatal extracorporeal membrane oxygenation: a review

BACKGROUND

Neonatal extracorporeal membrane oxygenation (ECMO) is a lifesaving therapeutic approach in newborns suffering from severe, but potentially reversible, respiratory insufficiency, mostly complicated by neonatal persistent pulmonary hypertension. However, cerebral damage, intracerebral hemorrhage as well as ischemia belong to the most devastating complications of ECMO.

OBJECTIVES

The objectives are to give insights into what is known from the literature concerning cerebral damage related to neonatal ECMO treatment for pulmonary reasons.

METHODS

A short introduction to ECMO indications and technical aspects of ECMO are provided for a better understanding of the process. The remainder of this review focuses on outcome and especially on (potential) risk factors for cerebral hemorrhage and ischemia during ECMO treatment.

RESULTS

Although neonatal ECMO treatment shows improved outcome compared to conservative treatment in cases of severe respiratory insufficiency, it is related to disturbances in various aspects of neurodevelopmental outcome. Risk factors for cerebral damage are either related to the patient's disease, EMCO treatment itself, or a combination of both.

CONCLUSION

It is of ongoing importance to further understand pathophysiological mechanisms resulting in cerebral hemorrhage and ischemia due to ECMO and to develop neuroprotective strategies and approaches.

Cerebral microbleeds after use of extracorporeal membrane oxygenation in children

Cerebral microbleeds (CMB) on gradient-recalled echo (GRE) magnetic resonance imaging (MRI) are rarely seen in children, yet have been described following vascular procedures in adults. Extracorporeal membrane oxygenation (ECMO) has been associated with vascular injury and neurological events in children, but there have been no reports to date of GRE MRI findings in children treated with ECMO. We reviewed MRI scans for all vascular neurology consultations in children treated with ECMO at an academic medical center over a 5-year period. In 6 of 12 cases, GRE was acquired as others were unstable or had contraindications to MRI. All 6 of 6 (100%) GRE cases (mean age 2.1 years, 7 female, 5 male) demonstrated CMB. CMB were multiple (>3 lesions), situated in cortical or lobar regions, with a striking predominance (5/6 cases) for the right carotid distribution. Other than CMB, no cases demonstrated intracranial hemorrhage. CMB may be noted on GRE MRI after ECMO and may reflect vascular damage from gaseous emboli.

Utility of neuroradiographic imaging in predicting outcomes after neonatal extracorporeal membrane oxygenation

BACKGROUND

The need for routine neuroimaging after extracorporeal membrane oxygenation (ECMO) and the optimal radiographic study remains unclear. We sought to evaluate the correlation between findings on head ultrasound (HUS) and magnetic resonance imaging (MRI) and determine the association of these findings to neurodevelopmental outcome.

METHODS

A retrospective review was performed (2003-2010) to identify neonates who had a MRI after ECMO. Each MRI was reviewed by a single pediatric neuroradiologist. Neurodevelopmental data was collected from the high-risk neonatal follow-up clinic.

RESULTS

Fifty neonates had a MRI (venoarterial 37, venovenous 13) after ECMO. HUS was abnormal in 24%, whereas MRI was abnormal in 62%. All infants with an abnormal HUS had an abnormal MRI, but an additional 50% of patients with a normal HUS had an abnormal MRI. Venoarterial ECMO was significantly associated with an abnormal MRI. Follow-up data was available for 26 neonates. The only predictor of abnormal neurodevelopment was the need for supplemental tube feeds at discharge.

CONCLUSIONS

MRI identified significantly more abnormalities compared to routine HUS after neonatal ECMO. However, neither MRI nor HUS findings correlated with early neurodevelopmental outcome. Feeding ability at discharge was the overall best predictor of neurologic impairment in survivors.

Neonatal ECMO Study of Temperature (NEST)--a randomised controlled trial

BACKGROUND

Existing evidence indicates that once mature neonates with severe cardio-respiratory failure become eligible for Extra Corporeal Membrane Oxygenation (ECMO) their chances of intact survival are doubled if they actually receive ECMO. However, significant numbers survive with disability. NEST is a multi-centre randomised controlled trial designed to test whether, in neonates requiring ECMO, cooling to 34 degrees C for the first 48 to 72 hours of their ECMO course leads to improved later health status. Infants allocated to the control group will receive ECMO at 37 degrees C throughout their course, which is currently standard practice around the world. Health status of both groups will be assessed formally at 2 years corrected age.

METHODS/DESIGN

All infants recruited to the study will be cared for in one of the four United Kingdom (UK) ECMO centres. Babies who are thought to be eligible will be assessed by the treating clinician who will confirm eligibility, ensure that consent has been obtained and then randomise the baby using a web based system, based at the National Perinatal Epidemiology Unit (NPEU) Clinical Trials Unit. Trial registration.Babies allocated ECMO without cooling will receive ECMO at 37 degrees C +/- 0.2 degrees C. Babies allocated ECMO with cooling will be managed at 34 degrees C +/- 0.2 degrees C for up to 72 hours from the start of their ECMO run. The minimum duration of cooling will be 48 hours. Rewarming (to 37 degrees C) will occur at a rate of no more than 0.5 degrees C per hour. All other aspects of ECMO management will be identical.

PRIMARY OUTCOME

Cognitive score from the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III) at age of 2 years (24 - 27 months).

DISCUSSION

For the primary analysis, children will be analysed in the groups to which they are assigned, comparing the outcome of all babies allocated to "ECMO with cooling" with all those allocated to "ECMO" alone, regardless of deviation from the protocol or treatment received. For the primary outcome the analysis will compare the mean scores for each group of surviving babies. The rationale for this choice of primary analysis is to give a fair representation of the average ability of assessable children, accepting the limitation that excluding deaths might impose.The consistency of the effect of cooling on the group of babies recruited to the trial will be explored to see whether cooling is of particular help, or not, to specific subgroups of infants, using the statistical test of interaction. Therefore pre-specified subgroup analyses include: (i) whether the ECMO is veno-arterial or veno-venous; (ii) whether the child's oxygenation index at the time of recruitment is <60 or > or = 60; (iii) initial aEEG pattern shown on the cerebral function monitor, and (iv) primary diagnostic group.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN72635512.

Effect of bladderbox alarms during venoarterial extracorporeal membrane oxygenation on cerebral oxygenation and hemodynamics in lambs

To determine the effects of bladderbox alarms during venoarterial extracorporeal membrane oxygenation (va-ECMO) on cerebral oxygenation and hemodynamics, six lambs were prospectively treated with va-ECMO and bladderbox alarms were simulated. Changes in concentrations of oxyhemoglobin (deltacO2Hb), deoxyhemoglobin (deltacHHb), and total Hb (deltactHb) were measured using near infrared spectrophotometry. Fluctuations in Hb oxygenation index (deltaHbD) and cerebral blood volume (deltaCBV) were calculated. Heart rate (HR), mean arterial pressure (MAP), blood flow in the left carotid artery (Qcar), and central venous pressure (CVP) were registered. Bladderbox alarms were simulated by increasing the ECMO flow or partially clamping the venous cannula and resolved by decreasing the ECMO flow, unclamping the cannula, or intravascular volume administration. CBV, HbD, MAP, and Qcar decreased significantly during bladderbox alarms, whereas HR and CVP increased. After the bladderbox alarms, CBV and HbD increased significantly to values above baseline. For HbD, this increase was higher during intravascular volume administration.MAP, Qcar, and CVP recovered to preexperiment values but increased further with volume administration. HR was increased at the end of our measurements. We conclude that Bladderbox alarms during va-ECMO treatment result in significant fluctuations in cerebral oxygenation and hemodynamics, a possible risk factor for intracranial lesions.

Extracorporeal membrane oxygenation in infants with congenital diaphragmatic hernia: follow-up MRI evaluating carotid artery reocclusion and neurologic outcome

OBJECTIVE

The purpose of our study was to prospectively assess, using MRI and MR angiography, the cerebral and vascular status of 2-year-old children with congenital diaphragmatic hernia (CDH) in whom carotid artery reconstruction was performed after neonatal extra-corporeal membrane oxygenation (ECMO) therapy and to compare the neurologic development of children with vascular reocclusion with that of CDH children with successful repair and with non-ECMO controls.

SUBJECTS AND METHODS

A total of 30 infants (17 boys, 13 girls; 2 +/- 0.26 years) were included. Of these, 18 (60%) infants received arteriovenous ECMO therapy with subsequent reconstruction of the right common carotid artery (RCCA). Two years postoperatively, the children were examined with cerebral MRI, including 3D time-of-flight and contrast-enhanced 3D MR angiography of the intra- and extracranial brain-supplying arteries. The pathologic findings were analyzed for the ability to predict impaired neurologic development.

RESULTS

The RCCA was occluded or highly stenotic in 13 (72%) of 18 children. All infants showed intra- and extracranial collaterals and a patent internal carotid artery. The average duration of ECMO was not longer than in cases of successful reconstruction (p = 1). The ECMO group showed a significantly greater incidence of cerebral injuries (p = 0.007) but no relevant impairment in neurologic development compared with controls (p = 0.26). Unsuccessful RCCA repair had no predictive value for a poor neurologic outcome (p = 1).

CONCLUSION

The outcome of RCCA repair after ECMO is possibly poorer than expected, with vascular occlusion or high-grade stenosis occurring in almost three quarters of patients. Although reocclusion of the RCCA does not increase the risk for cerebral lesions or an impaired neurologic development during the first 2 years postoperatively, the overall benefit of RCCA repair remains doubtful, and the potential long-term risk arising from these plaques has yet to be assessed.

The newborn drug development initiative workshop: Summary proceedings from the neurology group on neonatal seizures

BACKGROUND

The neonatal period eclipses all other epochs of the human life span for the highest incidence of seizures. Neonatal seizures are most commonly incited by serious acute illnesses such as hypoxic-ischemic encephalopathy, birth trauma, or infection.

OBJECTIVE

The goal of this article was to summarize some of the Neurology Group's discussion on neonatal seizures and their treatment with phenobarbital (PB).

METHODS

Information for this article was gathered from a workshop held March 29 and 30, 2004, in Baltimore, Maryland, as part of the Newborn Drug Development Initiative. A group of national experts was invited to form the Neurology Group to review certain aspects of neonatal seizures. Literature reviews were conducted using MEDLINE searches for original research studies, commentaries, and review articles between 1980 and 2004 using the key words neonatal seizures, treatment, and phenobarbital.

RESULTS

It has been empirically established that infants who experience seizures face substantially higher mortality and morbidity rates than those who do not. Basic research indicates that neonatal seizures themselves are not innocuous and actively contribute to adverse neurodevelopmental outcomes. Current worldwide clinical practice most often includes empiric treatment with PB for definite or suspected seizures in the newborn. Unfortunately, this common practice has never been proven by even a single, rigorous, randomized controlled trial. The Neurology Group identified the treatment of neonatal seizures with PB as an important topic in the practice of neonatal neurology for further investigation. Three possible frameworks for ethically acceptable, clinical treatment trials were explored. From these, a suitable scenario was selected-an electroencephalographer-blinded study of PB versus placebo in a homogeneous group of newborns who are at high risk of developing early subclinical electroencephalographic neonatal seizures (ENSs). Prospective video-electroencephalogram monitoring performed immediately after an insult (such as major cardiac surgery for a serious congenital heart defect) would establish the presence and number of subclinical ENSs. For a brief period of time, neonates with subclinical ENSs would be randomized to PB (dosed to match the PB-binding characteristics of the individual) or placebo. Clear criteria for escape from the study to active treatment are defined.

CONCLUSION

The investigation proposed here could refute or confirm the contemporary practice of PB administration as the first-line treatment of neonatal seizures.

Quantitative Electroencephalography Values of Neonates During and After Venoarterial Extracorporeal Membrane Oxygenation and Permanent Ligation of Right Common Carotid Artery

Venoarterial extracorporeal membrane oxygenation (ECMO) in neonates commonly needs neck vessel cannulation leading to ligation of right common carotid artery (RCCA) in some cases. Quantitative electroencephalography (EEG) measurements provide reproducible data of cerebral function. The aim of this case-control study was to test whether ligation of the RCCA results in EEG changes after ECMO weaning. Ten mechanically ventilated neonates not treated with ECMO were eligible as control patients. Seven ECMO patients receiving similar sedoanalgesia were investigated during and after ECMO and RCCA ligation. Dominant frequency, absolute alpha, theta, delta, and total powers of right and left frontocentral and temporooccipital derivations were calculated. Dominant frequency did not differ among groups. Power was found to be significantly decreased in all frequency bands during ECMO. After weaning from ECMO, EEG differences between the ECMO and control groups disappeared in spite of permanent RCCA ligation. It is concluded that ligation of the RCCA per se does not result in quantitative EEG changes.

Neonatal ECMO: neuroimaging and neurodevelopmental outcome

Intracranial injury continues to be a major complication associated with extracorporeal membrane oxygenation (ECMO)-treated neonates. The reported frequency of abnormal neuroimaging has ranged from 28% to 52%, depending on neuroimaging techniques and methods of classification. The purpose of this chapter is to describe types of imaging techniques commonly used to evaluate the ECMO neonate, to specify different types of injuries that have been reported, and to identify factors which increase the risk of injury. We will then describe the functional impact at age 5 years following neonatal brain injury among ECMO infants.

Primary use of the venovenous approach for extracorporeal membrane oxygenation in pediatric acute respiratory failure

OBJECTIVES

To describe a single center's experience with the primary use of venovenous cannulation for supporting pediatric acute respiratory failure patients with extracorporeal membrane oxygenation (ECMO).

DESIGN

Retrospective chart review of all patients receiving extracorporeal life support at a single institution.

SETTING

Pediatric intensive care unit at a tertiary care children's hospital.

PATIENTS

Eighty-two patients between the ages of 2 wks and 18 yrs with severe acute respiratory failure.

INTERVENTIONS

ECMO for acute respiratory failure.

MEASUREMENTS AND MAIN RESULTS

From January 1991 until April 2002, 82 pediatric patients with acute respiratory failure were cannulated for ECMO support. Median duration of ventilation before ECMO was 5 days (range, 1-17 days). Sixty-eight of these patients (82%) initially were placed on venovenous ECMO. Fourteen patients were initiated and remained on venoarterial support, including six in whom venovenous cannulae could not be placed. One patient was converted from venovenous to venoarterial support due to inadequate oxygenation. Venoarterial patients had significantly greater alveolar-arterial oxygen gradients and lower PaO(2)/FIO(2) ratios than venovenous patients (p <.03). Fifty-five of 81 venovenous patients received additional drainage cannulae (46 of 55 with an internal jugular cephalad catheter). Thirty-five percent of venovenous patients and 36% of venoarterial patients required at least one vasopressor infusion at time of cannulation (p = nonsignificant); vasopressor dependence decreased over the course of ECMO in both groups. Median duration on venovenous ECMO for acute hypoxemic respiratory failure was 218 hrs (range, 24-921). Venovenous ECMO survivors remained cannulated for significantly shorter time than nonsurvivors did (median, 212 vs. 350 hrs; p =.04). Sixty-three of 82 ECMO (77%) patients survived to discharge-56 of 68 venovenous ECMO (81%) and nine of 14 venoarterial ECMO (64%).

CONCLUSIONS

Venovenous ECMO can effectively provide adequate oxygenation for pediatric patients with severe acute respiratory failure receiving ECMO support. Additional cannulae placed at the initiation of venovenous ECMO could be beneficial in achieving flow rates necessary for adequate oxygenation and lung rest.

Outcome of infants with bronchopulmonary dysplasia who receive extracorporeal membrane oxygenation therapy

BACKGROUND/PURPOSE

Extracorporeal membrane oxygenation (ECMO) is an accepted therapy for acute respiratory failure but more recently has been used in infants with bronchopulmonary dysplasia (BPD) and superimposed acute pulmonary insults. The purpose of this study was to review the outcomes of such infants.

METHODS

Charts of infants at The Children's Hospital of Philadelphia (CHOP) who had a diagnosis of BPD before ECMO were reviewed. In addition, to obtain survival data in a larger population, the Extracorporeal Life Support Organization (ELSO) Registry was searched for infants with BPD before ECMO.

RESULTS

Of 204 patients who received noncardiac ECMO at CHOP, 9 had BPD before ECMO. Of 7 survivors, 4 were still ventilator dependent at 9 to 39 months of corrected age. Developmentally, 4 had significant global delays, whereas 3 had significant language and motor delays with average to mildly delayed cognitive abilities. The ELSO Registry search showed 76 patients with BPD before ECMO, with a 78% survival.

CONCLUSIONS

The survival rate of infants with BPD who receive ECMO is comparable to, or better than, the survival rates in most other ECMO populations. However, there appears to be a high risk of severe pulmonary and neurodevelopmental sequelae.

When combined, early bedside head ultrasound and electroencephalography predict abnormal computerized tomography or magnetic resonance brain images obtained after extracorporeal membrane oxygenation treatment

Definitive neuroimaging of the brain using computerized tomography (CT) or magnetic resonance imaging (MRI) in extracorporeal membrane oxygenation (ECMO)-treated infants must be delayed until after this therapy is completed. Bedside head ultrasound (HUS) and electroencephalography (EEG) studies during ECMO, if highly correlated with later definitive neuroimaging, might be used to affect the acute clinical care and early parental counseling of infants with severe cardiorespiratory failure. One hundred and sixty ECMO-treated patients had both bedside EEG and HUS studies performed during ECMO, as well as a later CT or MRI study prior to hospital discharge. There was a significant difference in CT or MRI findings among patients having normal studies on both the HUS and EEG, compared to those having an abnormality on either the HUS or the EEG, and compared to those having abnormalities on both studies. In ECMO-treated infants, the combination of a normal bedside HUS and an EEG without marked abnormalities is highly predictive of normal post-ECMO CT and MRI neuroimaging studies.

Clinical antecedents of neurologic and audiologic abnormalities in survivors of neonatal extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation is an effective rescue treatment for severe cardiorespiratory failure in term or near term neonates, although cerebral palsy, mental retardation, and sensorineural hearing loss are observed in 10 to 20% of survivors. The objective of the present study was to identify potential risk factors that may explain the neurologic and audiologic sequelae noted in 19% of 181 survivors of neonatal extracorporeal membrane oxygenation from our hospital. Our results suggest the following findings in survivors of severe cardiorespiratory failure treated with neonatal extracorporeal membrane oxygenation: (1) hypotension or the need for cardiopulmonary resuscitation before extracorporeal membrane oxygenation significantly increases the risk of spastic cerebral palsy, (2) profound hypocarbia before extracorporeal membrane oxygenation is associated with a significantly increased risk of hearing loss, (3) mental retardation in the absence of spastic cerebral palsy is unexplained except when due to abnormal fetal brain development, and (4) hypoxemia in the absence of hypotension does not increase the risk of neurologic or audiologic sequelae.

Carotid artery and jugular vein ligation with and without hypoxia in the rat

A continuing concern about the use of extracorporeal membrane oxygenation (ECMO) is the cannulation of the common carotid artery or the internal jugular vein. The authors investigated the changes that might occur in the brain with neck vessel ligation in the normal and the hypoxic rat. Two groups of 60 rats each were studied. The first group was divided into three subgroups of 20 animals each. Subgroup 1 (HH) was hypoxic both 24 hours before and 24 hours after operation. Subgroup 2 (HN) (the ECMO model) was hypoxic before operation and recovered for 24 hours in room air. Subgroup 3 (NN) underwent the entire procedure in room air. For each oxygen environment, four different operations were performed: carotid artery ligation, jugular vein ligation, carotid artery and jugular vein ligation, and dissection of the vessels without ligation (sham). Thus each subgroup was further divided into four sub-subgroups based on the operation performed. Rats were again anesthetized after a 24-hour recovery period and killed using low, blunt cervical dislocation. In the first group of 60 rats, the skull was opened and the brain was carefully removed from the cranial vault and placed in a fixative. The brains were placed in a small magnetic resonance imaging (MRI) head coil in groups of five and scans were obtained to provide T1 and T2 images that correlated with histological sections. MRI scans were reviewed in random, blinded fashion by an imager unaware of how these animals had been treated. The brains were then sectioned coronally at six corresponding levels: frontal, mid and posterior cerebrum, midbrain, pons, and medulla. Histological examination was performed in blinded fashion. The number of lesions (usually ischemic as noted by a decrease in the number of neurons) was totaled for each area of the brain. There were no differences that were consistent or statistically significant in the MR images of brains removed from the head, although it would appear that rats with jugular vein and carotid artery ligation were relatively protected. In the HN group jugular vein ligation was worst, and adding carotid artery ligation was best. In the histological studies the NN group had significantly more lesions than the HH group (P < .01). The second group of 60 rats was divided and treated as the first group in all respects except that MRI was conducted immediately after death on intact heads, and no histological studies were performed. This was done to control for lesions that might have been produced by removal of the brains from the skulls. In this group all findings were right sided. One animal in the HN group showed midcerebral white matter edema after jugular and carotid ligation. Focal anterior cerebral edema was seen in another animal (HH) after isolated carotid ligation. An occipital infarct was found in one animal (HH) after both carotid and jugular ligation. The authors conclude that neck vessel ligation in the hypoxic or normoxic rat causes only occasional and sporadic brain injury much as is seen clinically in newborn ECMO patients.

Purine metabolism and inhibition of xanthine oxidase in severely hypoxic neonates going onto extracorporeal membrane oxygenation

The effect of allopurinol to inhibit purine metabolism via the xanthine oxidase pathway in neonates with severe, progressive hypoxemia during rescue and reperfusion with extracorporeal membrane oxygenation (ECMO) was examined. Twenty-five term infants meeting ECMO criteria were randomized in a double-blinded, placebo-controlled trial. Fourteen did not receive allopurinol, whereas 11 were treated with 10 mg/kg after meeting criteria and before cannulation, in addition to a 20-mg/kg priming dose to the ECMO circuit. Infant plasma samples before cannulation, and at 15, 30, 60, and 90 min, and 3, 6, 9, and 12 h on bypass were analyzed (HPLC) for allopurinol, oxypurinol, hypoxanthine, xanthine, and uric acid concentrations. Urine samples were similarly evaluated for purine excretion. Hypoxanthine concentrations in isolated blood-primed ECMO circuits were separately measured. Hypoxanthine, xanthine, and uric acid levels were similar in both groups before ECMO. Hypoxanthine was higher in allopurinol-treated infants during the time of bypass studied (p = 0.022). Xanthine was also elevated (p < 0.001), and uric acid was decreased (p = 0.005) in infants receiving allopurinol. Similarly, urinary elimination of xanthine increased (p < 0.001), and of uric acid decreased (p = 0.04) in treated infants. No allopurinol toxicity was observed. Hypoxanthine concentrations were significantly higher in isolated ECMO circuits and increased over time during bypass (p < 0.001). This study demonstrates that allopurinol given before cannulation for and during ECMO significantly inhibits purine degradation and uric acid production, and may reduce the production of oxygen free radicals during reoxygenation and reperfusion of hypoxic neonates recovered on bypass.