Cerebral blood flow and oxygenation during venoarterial and venovenous extracorporeal membrane oxygenation in the newborn lamb

Brain injury plasma biomarkers in patients on veno-arterial extracorporeal membrane oxygenation: A pilot prospective observational study

INTRODUCTION

Early diagnosis of acute brain injury (ABI) is critical for patients on veno-arterial extracorporeal membrane oxygenation (V-A ECMO) to guide anticoagulation strategy; however, neurological assessment in ECMO is often limited by patient sedation.

METHODS

In this pilot study of adults from June 2018 to May 2019, plasma samples of glial fibrillary acidic protein (GFAP), neurofilament light chain (NFL), and tubulin associated unit (Tau) were collected daily after V-A ECMO cannulation and measured using a multiplex platform. Primary outcomes were occurrence of ABI, assessed clinically, and neurologic outcome, assessed by modified Rankin Scale (mRS).

RESULTS

Of 20 consented patients (median age = 48.5°years; 55% female), 8 (40%) had ABI and 15 (75%) had unfavorable neurologic outcome at discharge. 10 (50%) patients were centrally cannulated. Median duration on ECMO was 4.5°days (IQR: 2.5-9.5). Peak GFAP, NFL, and Tau levels were higher in patients with ABI vs. without (AUC = 0.77; 0.85; 0.57, respectively) and in patients with unfavorable vs. favorable neurologic outcomes (AUC = 0.64; 0.59; 0.73, respectively). GFAP elevated first, NFL elevated to the highest degree, and Tau showed limited change regardless of ABI.

CONCLUSION

Further studies are warranted to determine how plasma biomarkers may facilitate early detection of ABIs in V-A ECMO to assist timely clinical decision-making.

Comorbidities and Late Outcomes in Neonatal Pulmonary Hypertension

Long-term outcomes of persistent pulmonary hypertension of newborn (PPHN) depend on disease severity, duration of ventilation, and associated anomalies. Congenital diaphragmatic hernia survivors may have respiratory morbidities and developmental delay. The presence of PPHN is associated with increased mortality in hypoxic-ischemic encephalopathy, though the effects on neurodevelopment are less clear. Preterm infants can develop pulmonary hypertension (PH) early in the postnatal course or later in the setting of bronchopulmonary dysplasia (BPD). BPD-PH is associated with higher mortality, particularly within the first year. Evidence suggests that both early and late PH in preterm infants are associated with neurodevelopmental impairment.

Gaseous Nitric Oxide-Cangrelor Combination to Prevent Clots in Extracorporeal Life Support System

INTRODUCTION

The objective of this study was to investigate the potential synergistic utility of a combination of gaseous nitric oxide (gNO)-intravenous Cangrelor as an effective pharmacological option for the prevention of thrombosis in an animal model of extracorporeal life support (ECLS) circuits.

METHODS

10 newborn lambs were placed on ECLS. 5 of them were administered a combination of gNO and intravenous Cangrelor. The remaining 5 were not administered any anticoagulant. The primary end point was duration of ECLS without clot formation. The secondary outcome measure was the absolute maximum transmembrane pressure gradient.

RESULTS

The mean duration of ECLS were 168 min (standard deviation 224.98 min) in the control group and 402 min (standard deviation 287.5 min) in the experimental group (P = 0.17). The peak trans-oxygenator pressure difference was 43 mm Hg (standard deviation 23 mm Hg) in the control group and 62 mm Hg (standard deviation 71 mm Hg) in the experimental group(P = 0.64). Two animals in the experimental group were supported up to 12 h without clot formation. Clot formation in the experimental group occurred after placement of the cannulae but prior to initiation of ECLS flows after cannulation.

CONCLUSIONS

A combination of gNO and Cangrelor is prevents clot formation in an experimental animal model when administered through a clean clot-free circuit. However, the combination s ineffective when there are pre-existing clots in the circuit. A bolus of anticoagulation prior to cannulation is needed prior to testing this combination in future studies with a larger sample size.

Neonatal Carotid Artery and Internal Jugular Vein Management Practices at Extracorporeal Membrane Oxygenation Decannulation: No Standard Approach

BACKGROUND

There are currently no commonly accepted standardized guidelines for management of cervical vessels at neonatal extracorporeal membrane oxygenation (ECMO) decannulation. This study investigates neonatal ECMO decannulation practices regarding management of the carotid artery and internal jugular vein, use of post-repair anticoagulation, and follow-up imaging.

METHODS

A survey was distributed to the 37 institutions in the Children's Hospitals Neonatal Consortium. Respondents reported their standard approach to carotid artery and internal jugular vein management (ligation or repair) at ECMO decannulation by their pediatric surgery and cardiothoracic (CT) surgery teams as well as post-repair anticoagulation practices and follow-up imaging protocols.

RESULTS

The response rate was 95%. Pediatric surgeons performed most neonatal respiratory ECMO cannulations (88%) and decannulations (85%), while all neonatal cardiac ECMO cannulations and decannulations were performed by CT surgeons. Pediatric surgeons overwhelmingly ligate both vessels (90%) while CT surgeons typically repair both vessels at decannulation (83%). Of the responding centers that repair, 28% (7) have a standard anticoagulation protocol after neck vessel repair. While 52% (13) of centers routinely image cervical vessel patency at least once post repair, most do not subsequently repeat neck vessel imaging.

CONCLUSIONS

Significant practice differences exist between pediatric and CT surgeons regarding the approach to cervical vessels at neonatal ECMO decannulation. For those centers that do repair the vessels there is little uniformity in post-repair anticoagulation or imaging protocols. There is a need to develop standardized cervical vessel management guidelines for neonatal ECMO patients and to study their impact on both short- and long-term outcomes.

LEVEL OF EVIDENCE

IV.

Pediatric ECLS Neurologic Management and Outcomes

Neurologic complications associated with extracorporeal life support (ECLS), including seizures, ischemia/infarction, and intracranial hemorrhage significantly increase morbidity and mortality in pediatric and neonatal patients. Prompt recognition of adverse neurologic events may provide a window to intervene with neuroprotective measures. Many neuromonitoring modalities are available with varying benefits and limitations. Several pre-ECLS and ECLS-related factors have been associated with an increased risk for neurologic complications. These may be patient- or circuit-related and include modifiable and non-modifiable factors. ECLS survivors are at risk for long-term neurological sequelae affecting neurodevelopmental outcomes. Possible long-term outcomes range from normal development to severe impairment. Patients should undergo a neurological evaluation prior to discharge, and neurodevelopmental assessments should be included in each patient's structured, multidisciplinary follow-up. Safe pediatric and neonatal ECLS management requires a thorough understanding of neurological complications, neuromonitoring techniques and limitations, considerations to minimize risk, and an awareness of possible long-term ramifications. With a focus on ECLS for respiratory failure, this manuscript provides a review of these topics and summarizes best practice guidelines from international organizations and expert consensus.

Utility of Cerebral Microvascular Imaging in Infants Undergoing ECMO

PURPOSE

Infants who require extracorporeal membrane oxygenation (ECMO) therapy have an increased risk of neurological complications and mortality. Microvascular imaging (MVI) is an advanced Doppler technique that allows high-resolution visualization of microvasculature in the brain. We describe the feasibility and utility of MVI for the evaluation of cerebral microvascular perfusion in patients undergoing ECMO.

METHODS

We retrospectively analyzed brain MVI scans of neonates undergoing ECMO. Two pediatric radiologists qualitatively assessed MVI scans to determine the presence or absence of tortuosity, symmetry, heterogeneity, engorgement, and hypoperfusion of the basal ganglia-thalamus (BGT) region, as well as the presence or absence of white matter vascular engorgement and increased peri-gyral flow in the cortex. We tested the association between the presence of the aforementioned brain MVI features and clinical outcomes.

RESULTS

We included 30 patients, 14 of which were male (46.7%). The time of ECMO duration was 11.8 ± 6.9 days. The most prevalent microvascular finding in BGT was lenticulostriate vessel tortuosity (26/30, 86.7%), and the most common microvascular finding in the cortex was increased peri-gyral flow (10/24, 41.7%). Cortical white matter vascular engorgement was significantly associated with the presence of any poor outcome as defined by death, seizure, and/or cerebrovascular events on magnetic resonance imaging (p = 0.03).

CONCLUSION

MVI is a feasible modality to evaluate cerebral perfusion in infants undergoing ECMO. Additionally, evidence of white matter vascular engorgement after ECMO cannulation could serve as a predictor of poor outcomes in this population.

Current understanding and future potential applications of cerebral microvascular imaging in infants

Microvascular imaging is an advanced Doppler ultrasound technique that detects slow flow in microvessels by suppressing clutter signal and motion-related artifacts. The technique has been applied in several conditions to assess organ perfusion and lesion characteristics. In this pictorial review, we aim to describe current knowledge of the technique, particularly its diagnostic utility in the infant brain, and expand on the unexplored but promising clinical applications of microvascular imaging in the brain with case illustrations.

Utility of cephalic drains in infants receiving extracorporeal membrane oxygenation

INTRODUCTION

The addition of cephalic drains (CDs) in extracorporeal membrane oxygenation (ECMO) to augment venous drainage may offer benefit, though their use is varied. Our objective was to describe our institution's experience with CDs including flow rates and patency. We also compared complication rates between patients with and without a CD.

METHODS

This retrospective cohort study included infants <12 months of age cannulated for ECMO between January 1, 2010 and September 30, 2019 at a single institution. Flow data were obtained for those with a CD. Demographic and complication rates were obtained for all.

RESULTS

Of 264 patients in the final cohort, 220 (83%) had a CD of which 93.2% remained patent to decannulation. CDs typically provided 30% or more of ECMO flow throughout the ECMO run. The median time to CD clot was 139 h (range 48-635 h). Patients with a clotted CD had longer ECMO runs than those whose CD remained patent (median 382 h [IQR 217-538] vs 139 h [IQR 91-246], p < 0.001). Survival to discharge was lower for those with clotted versus patent CD (14% vs 70%, p < 0.001). Mechanical complications were more common in patients with CD (p = 0.005). Seizures were more common in those without a CD (p = 0.021).

CONCLUSIONS

In this cohort, the majority of CDs placed remained patent at decannulation and provided substantial additional venous drainage. Mechanical problems were common in patients with CDs, but without clinical sequelae. Further study is warranted to elucidate CD impact on short- and long-term outcomes.

Cerebrovascular autoregulation and arterial carbon dioxide in patients with acute respiratory distress syndrome: a prospective observational cohort study

BACKGROUND

Early hypercapnia is common in patients with acute respiratory distress syndrome (ARDS) and is associated with increased mortality. Fluctuations of carbon dioxide have been associated with adverse neurological outcome in patients with severe respiratory failure requiring extracorporeal organ support. The aim of this study was to investigate whether early hypercapnia is associated with impaired cerebrovascular autoregulation during the acute phase of ARDS.

METHODS

Between December 2018 and November 2019, patients who fulfilled the Berlin criteria for ARDS, were enrolled. Patients with a history of central nervous system disorders, cerebrovascular disease, chronic hypercapnia, or a life expectancy of less than 24 h were excluded from study participation. During the acute phase of ARDS, cerebrovascular autoregulation was measured over two time periods for at least 60 min. Based on the values of mean arterial blood pressure and near-infrared spectroscopy, a cerebral autoregulation index (COx) was calculated. The time with impaired cerebral autoregulation was calculated for each measurement and was compared between patients with and without early hypercapnia [defined as an arterial partial pressure of carbon dioxide (PaCO2) ≥ 50 mmHg with a corresponding arterial pH < 7.35 within the first 24 h of ARDS diagnosis].

RESULTS

Of 66 patients included, 117 monitoring episodes were available. The mean age of the study population was 58.5 ± 16 years. 10 patients (15.2%) had mild, 28 (42.4%) moderate, and 28 (42.4%) severe ARDS. Nineteen patients (28.8%) required extracorporeal membrane oxygenation. Early hypercapnia was present in 39 patients (59.1%). Multivariable analysis did not show a significant association between early hypercapnia and impaired cerebrovascular autoregulation (B = 0.023 [95% CI - 0.054; 0.100], p = 0.556). Hypocapnia during the monitoring period was significantly associated with impaired cerebrovascular autoregulation [B = 0.155 (95% CI 0.014; 0.296), p = 0.032].

CONCLUSION

Our results suggest that moderate permissive hypercapnia during the acute phase of ARDS has no adverse effect on cerebrovascular autoregulation and may be tolerated to a certain extent to achieve low tidal volumes. In contrast, episodes of hypocapnia may compromise cerebral blood flow regulation. Trial registration ClinicalTrials.gov; registration number: NCT03949738; date of registration: May 14, 2019.

Cerebral Oxygenation of Premature Lambs Supported by an Artificial Placenta

An artificial placenta (AP) using venovenous extracorporeal life support (VV-ECLS) could represent a paradigm shift in the treatment of extremely premature infants. However, AP support could potentially alter cerebral oxygen delivery. We assessed cerebral perfusion in fetal lambs on AP support using near-infrared spectroscopy (NIRS) and carotid arterial flow (CAF). Fourteen premature lambs at estimated gestational age (EGA) 130 days (term = 145) underwent cannulation of the right jugular vein and umbilical vein with initiation of VV-ECLS. An ultrasonic flow probe was placed around the right carotid artery (CA), and a NIRS sensor was placed on the scalp. Lambs were not ventilated. CAF, percentage of regional oxygen saturation (rSO2) as measured by NIRS, hemodynamic data, and blood gases were collected at baseline (native placental support) and regularly during AP support. Fetal lambs were maintained on AP support for a mean of 55 ± 27 hours. Baseline rSO2 on native placental support was 40% ± 3%, compared with a mean rSO2 during AP support of 50% ± 11% (p = 0.027). Baseline CAF was 27.4 ± 5.4 ml/kg/min compared with an average CAF of 23.7 ± 7.7 ml/kg/min during AP support. Cerebral fractional tissue oxygen extraction (FTOE) correlated negatively with CAF (r = -0.382; p < 0.001) and mean arterial pressure (r = -0.425; p < 0.001). FTOE weakly correlated with systemic O2 saturation (r = 0.091; p = 0.017). Cerebral oxygenation and blood flow in premature lambs are maintained during support with an AP. Cerebral O2 extraction is inversely related to carotid flow and is weakly correlated with systemic O2 saturation.

Cerebrovascular Physiology During Pediatric Extracorporeal Membrane Oxygenation: A Multicenter Study Using Transcranial Doppler Ultrasonography

OBJECTIVES

To explore changes to expected, age-related transcranial Doppler ultrasound variables during pediatric extracorporeal membrane oxygenation.

DESIGN

Prospective, observational, multicenter study.

SETTING

Tertiary care PICUs.

PATIENTS

Children 1 day to 18 years old requiring veno arterial extracorporeal membrane oxygenation.

METHODS

Participants underwent daily transcranial Doppler ultrasound measurement of bilateral middle cerebral artery flow velocities. Acute neurologic injury was diagnosed if seizures, cerebral hemorrhage, or diffuse cerebral ischemia was detected.

MEASUREMENTS AND MAIN RESULTS

Fifty-two children were enrolled and analyzed. In the 44 children without acute neurologic injury, there was a significant reduction in systolic flow velocity and mean flow velocity compared with predicted values over time (F [8, 434] = 60.44; p ≤ 0.0001, and F [8, 434] = 17.61; p ≤ 0.0001). Middle cerebral artery systolic flow velocity was lower than predicted on extracorporeal membrane oxygenation days 1-5, and mean flow velocity was lower than predicted on extracorporeal membrane oxygenation days 1-3. In the six infants less than 90 days old suffering diffuse cerebral ischemia, middle cerebral artery systolic flow velocity, mean flow velocity, and diastolic flow velocity from extracorporeal membrane oxygenation days 1-9 were not significantly different when compared with children of similar age in the cohort that did not suffer acute neurologic injury (systolic flow velocity F [8, 52] = 0.6659; p = 0.07 and diastolic flow velocity F [8, 52] = 1.4; p = 0.21 and mean flow velocity F [8, 52] = 1.93; p = 0.07). Pulsatility index was higher in these infants over time than children of similar age in the cohort on extracorporeal membrane oxygenation that did not suffer acute neurologic injury (F [8, 52] = 3.1; p = 0.006). No patient in the study experienced cerebral hemorrhage.

CONCLUSIONS

Flow velocities in the middle cerebral arteries of children requiring extracorporeal membrane oxygenation are significantly lower than published normative values for critically ill, mechanically ventilated, sedated children. Significant differences in measured systolic flow velocity, diastolic flow velocity, and mean flow velocity were not identified in children suffering ischemic injury compared with those who did not. However, increased pulsatility index may be a marker for ischemic injury in young infants on extracorporeal membrane oxygenation.

Influence of cannula positioning on brain injury during extracorporeal membrane oxygenation

Background

In veno-arterial extracorporeal membrane oxygenation (V-A ECMO), a patient is cannulated using either an atrio-aortic technique (central type ECMO; cECMO) or a femoro-femoral technique (peripheral type ECMO; pECMO). The direction of the pump flow at the aortic arch is anterograde from the ascending aorta in cECMO and retrograde from the descending aorta in pECMO. Hemodynamic differences from the position of the cannulas may influence the brain differently. To evaluate the effect of ECMO cannula positioning on the brain, hemodynamic data and plasma biomarkers were collected.

Methods

Eight pigs were randomly divided into the cECMO group (n=4) or pECMO group (n=4). ECMO was administered for 6 hours at a pump flow rate based on the mean flow of the ascending aorta. Mean arterial pressure (MAP), mean arterial flow (MAF), energy equivalent pressure (EEP), and surplus hemodynamic energy (SHE) were measured in the brachiocephalic artery every 30 minutes. During ECMO treatment, plasma was collected for analysis of interleukin-6 (IL-6), S100B, glial fibrillary acidic protein (GFAP), and neuron-specific enolase. The data were analyzed using the Mann-Whitney U tests, and repeated measures ANOVAs; significance was set at P<0.05.

Results

MAP and EEP at 1 and at 3 hours, MAF at all measured times, and SHE at 1 hour and 6 hours were significantly higher in the pECMO group. There was no significant difference in the levels of brain injury biomarkers between cECMO and pECMO groups.

Conclusions

The hemodynamic data showed that pECMO was superior to cECMO. Based on the biomarker data, neither pECMO nor cECMO for 6 hours caused evidence of brain injury.

Effects of an artificial placenta on brain development and injury in premature lambs

PURPOSE

We evaluated whether brain development continues and brain injury is prevented during Artificial Placenta (AP) support utilizing extracorporeal life support (ECLS).

METHODS

Lambs at EGA 118days (term=145; n=4) were placed on AP support (venovenous ECLS with jugular drainage and umbilical vein reinfusion) for 7days and sacrificed. Early (EGA 118; n=4) and late (EGA 127; n=4) mechanical ventilation (MV) lambs underwent conventional MV for up to 48h and were sacrificed, and early (n=5) and late (n=5) tissue control (TC) lambs were sacrificed at delivery. Brains were harvested, formalin-fixed, rehydrated, and studied by magnetic resonance imaging (MRI). The gyrification index (GI), a measure of cerebral folding complexity, was calculated for each brain. Diffusion-weighted imaging was used to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in multiple structures to assess white matter (WM) integrity.

RESULTS

No intracranial hemorrhage was observed. GI was similar between AP and TC groups. ADC and FA did not differ between AP and late TC groups in any structure. Compared to late MV brains, AP brains demonstrated significantly higher ADC (0.45±0.08 vs. 0.27±0.11, p=0.02) and FA (0.61±0.04 vs. 0.44±0.05; p=0.006) in the cerebral peduncles.

CONCLUSIONS

After 7days of AP support, WM integrity is preserved relative to mechanical ventilation.

TYPE OF STUDY

Research study.

ECMO Maintains Cerebral Blood Flow During Endotoxic Shock in Piglets

Cerebrovascular injury while on extracorporeal membrane oxygenation (ECMO) may be caused by excessive brain perfusion during hypoxemic reperfusion. Previous studies have postulated that the most vulnerable period of time for cerebrovascular injury is during the transfer period to ECMO. Therefore, our objective was to compare brain perfusion and hemodynamics in a piglet endotoxic shock ECMO model. The effect of ECMO flow on microcirculation of different brain regions was compared between 10 control pigs and six pigs (7–10 kg) administered IV endotoxin to achieve a drop in mean arterial blood pressure (MAP) of at least 30%. Cardiac output (CO), brain oxygen utilization, and microcirculatory blood flow (BF) were compared at baseline and 2 hours after ECMO stabilization. Matching ECMO delivery with baseline CO in control animals increased perfusion (p < 0.05) in all areas of the brain. In contrast, with endotoxin, ECMO returned perfusion closer to baseline levels in all regions of the brain and maintained brain tissue oxygen consumption. Both control and endotoxic pigs showed no evidence of acute neuronal necrosis in histologic cerebral cortical sections examined after 2 hours of ECMO. Results show that during endotoxic shock, transition to ECMO can maintain brain BF equally to all brain regions without causing overperfusion, and does not appear to cause brain tissue histopathologic changes (hemorrhage or necrosis) during the acute stabilization period after ECMO induction.

Extracorporeal membrane oxygenation and cerebral blood flow velocity in children

OBJECTIVE

To determine how extracorporeal membrane oxygenation affects cerebral blood flow velocity and to determine whether specific changes in cerebral blood flow velocity may be associated with neurologic injury.

DESIGN

Prospective, observational study.

SETTING

PICU in a tertiary care academic center.

PATIENTS

Children (age less than or equal to 18 yr) requiring extracorporeal membrane oxygenation support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Eighteen patients (age 3.8 ± 7.2 years; venovenous neck, n = 5; venoarterial neck, n = 8; venoarterial chest, n = 5) requiring extracorporeal membrane oxygenation underwent daily transcranial Doppler ultrasound measurements of cerebral blood flow velocity in bilateral middle cerebral arteries. Cerebral blood flow velocity measurements were recorded as a percentage of age and gender normal value. On extracorporeal membrane oxygenation, cerebral blood flow velocities in patients not suffering clinically evident neurologic injury were decreased with systolic flow velocity (Vs) 54% ± 3% predicted and mean flow velocity (Vm) 52% ± 4% predicted. After decannulation, Vs and Vm were higher than while on extracorporeal membrane oxygenation at 73% ± 3% predicted (p = 0.0007 vs. value on extracorporeal membrane oxygenation) and 64% ± 4% predicted (p = 0.01 vs. value on extracorporeal membrane oxygenation).Patients who developed clinically evident cerebral hemorrhage had higher Vs, diastolic flow velocity (Vd), and Vm compared with those who did not: 123% ± 8% predicted, 130% ± 18% predicted, 127% ± 9% predicted (p < compared to values in children not suffering neurological injury). Supranormal flow velocities were noted 2-6 days before clinical recognition of cerebral hemorrhage in all four patients. There were no significant differences in mean arterial blood pressure, circuit flow, or hematocrit between the children who suffered cerebral hemorrhage and those who did not. Partial pressure of carbon dioxide was lower in the group of patients who experienced cerebral hemorrhage than in those who did not (38 ± 2 vs. 44 ± 1 mm Hg, p = 0.03).

CONCLUSION

In children who did not suffer clinically apparent neurologic injury, cerebral blood flow velocities were lower than normal while on extracorporeal membrane oxygenation support and increased after decannulation. However, children who developed cerebral hemorrhage had higher than normal cerebral blood flow velocities noted for days prior to clinical recognition of bleeding. Cerebral blood flow velocity measurement may represent a portable, noninvasive way to predict cerebral complications of extracorporeal membrane oxygenation and deserves further study.

Development of an artificial placenta V: 70 h veno-venous extracorporeal life support after ventilatory failure in premature lambs

PURPOSE

An artificial placenta would change the paradigm of treating extremely premature infants. We hypothesized that using a veno-venous extracorporeal life support (VV-ECLS) artificial placenta after ventilatory failure would stabilize premature lambs and maintain normal fetal physiologic parameters for 70 h.

METHODS

A near-term neonatal lamb model (130 days; term=145) was used. The right jugular vein (drainage) and umbilical vein (reinfusion) were cannulated with 10-12 Fr cannulas. Lambs were then transitioned to an infant ventilator. After respiratory failure, the endotracheal tube was filled with amniotic fluid, and VV-ECLS total artificial placenta support (TAPS) was initiated. Lambs were maintained on TAPS for 70 h.

RESULTS

Six of seven lambs survived for 70 h. Mean ventilation time was 57 ± 22 min. During ventilation, mean MAP was 51 ± 14 mmHg, compared to 44 ± 14 mmHg during TAPS (p=0.001). Mean pH and lactate during ventilation were 7.06 ± 0.15 and 5.7 ± 2.3 mmol/L, compared to 7.33 ± 0.07 and 2.0 ± 1.8 mmol/L during TAPS (p<0.001 for both). pO(2) and pCO(2) remained within normal fetal parameters during TAPS, and mean carotid blood flow was 25 ± 7.5 mL/kg/min. Necropsy showed a patent ductus arteriosus and no intracranial hemorrhage in all animals.

CONCLUSIONS

The artificial placenta stabilized premature lambs after ventilatory failure and maintained fetal circulation, hemodynamic stability, gas exchange, and cerebral perfusion for 70 h.

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.

Perioperative mechanical circulatory support in children with critical heart disease

OPINION STATEMENT

The treatment of cardiovascular failure in the perioperative period with the use of mechanical circulatory support is a well-recognized, well-developed, and commonly utilized treatment modality. Regardless of the exact circumstances of initiation, the use of a support device is a "bridge." Where there has been an acute myocardial insult, short-term assist devices can serve as a "bridge to immediate survival," a "bridge to recovery," or even a "bridge to the next decision." Mechanical circulatory support can serve as a treatment of cardiovascular decompensation caused by myocarditis, acute myocardial insult, low cardiac output following surgery, and congenital heart disease. The utilization of such support carries significant risks such as bleeding, infection, and thrombosis. However, these can be minimized in order to allow for the safe and effective deployment of this therapeutic strategy. One specific therapeutic domain in which these devices provide immediate impact is during cardiac arrest. Although outcomes of cardiac arrest remain poor, use of a mechanical device as an intervention has allowed salvage of otherwise certain mortality. However, it is important to note that the utility of support was most pronounced in patients that were not on either extreme of the survival prediction curve. This can be best summarized by the concept of "not too early, not too late." Therefore, it is the responsibility of the entire care team to find the appropriate patient population in which to "pull the trigger" on mechanical support as a therapy. This decision point is supported by a monitoring strategy that can be utilized to predict deterioration and intervene adequately. Most importantly, an effective monitoring strategy allows the practitioner to judge the effectiveness of treatment and support strategies and make adjustments in a timely manner, potentially with mechanical support in the perioperative period.

Glial fibrillary acidic protein as a brain injury biomarker in children undergoing extracorporeal membrane oxygenation

OBJECTIVE

To determine whether, in children, plasma glial fibrillary acidic protein is associated with brain injury during extracorporeal membrane oxygenation and with mortality.

DESIGN

Prospective, observational study.

SETTING

Pediatric intensive care unit in an urban tertiary care academic center.

PATIENTS

Neonatal and pediatric patients on extracorporeal membrane oxygenation (n = 22).

INTERVENTIONS

Serial blood sampling for glial fibrillary acidic protein measurements.

MEASUREMENTS AND MAIN RESULTS

Prospective patients age 1 day to 18 yrs who required extracorporeal membrane oxygenation from April 2008 to August 2009 were studied. Glial fibrillary acidic protein was measured using an electrochemiluminescent immunoassay developed at Johns Hopkins. Control samples were collected from 99 healthy children (0.5-16 yrs) and 59 neonatal intensive care unit infants without neurologic injury. In controls, the median glial fibrillary acidic protein concentration was 0.055 ng/mL (interquartile range, 0-0.092 ng/mL) and the 95th percentile of glial fibrillary acidic protein was 0.436 ng/mL. In patients on extracorporeal membrane oxygenation, plasma glial fibrillary acidic protein was measured at 6, 12, and every 24 hrs after cannulation. We enrolled 22 children who underwent extracorporeal membrane oxygenation. Median age was 7 days (interquartile range, 2 days to 9 yrs), and primary extracorporeal membrane oxygenation indication was: cardiac failure, six of 22 (27.3%); respiratory failure, 12 of 22 (54.5%); extracorporeal cardiopulmonary resuscitation, three of 22 (13.6%); and sepsis, one of 22 (4.6%). Seven of 22 (32%) patients developed acute neurologic injury (intracranial hemorrhage, brain death, or cerebral edema diagnosed by imaging). Fifteen of 22 (68%) survived to hospital discharge. In the extracorporeal membrane oxygenation group, peak glial fibrillary acidic protein levels were higher in children with brain injury than those without (median, 5.9 vs. 0.09 ng/mL, p = .04) and in nonsurvivors compared with survivors to discharge (median, 5.9 vs. 0.09 ng/mL, p = .04). The odds ratio for brain injury for glial fibrillary acidic protein >0.436 ng/mL vs. normal was 11.5 (95% confidence interval, 1.3-98.3) and the odds ratio for mortality was 13.6 (95% confidence interval, 1.7-108.5).

CONCLUSIONS

High glial fibrillary acidic protein during extracorporeal membrane oxygenation is significantly associated with acute brain injury and death. Brain injury biomarkers may aid in outcome prediction and neurologic monitoring of patients on extracorporeal membrane oxygenation to improve outcomes and benchmark new therapies.

Correlation of brain tissue oxygen tension with cerebral near-infrared spectroscopy and mixed venous oxygen saturation during extracorporeal membrane oxygenation

The aim of this prospective, animal study was to compare brain tissue oxygen tension (PbtO(2)) with cerebral near infrared spectroscopy (NIRS) and mixed venous oxygen saturation (SVO(2)) during venoarterial extracorporeal membrane oxygenation (VA ECMO) in a porcine model. This was accomplished using twelve immature piglets with surgically implanted catheters placed in the superficial cerebral cortex to measure brain PbtO(2) and microdialysis metabolites. The NIRS sensor was placed overlying the forehead to measure cerebral regional saturation index (rSO(2)i) while SVO(2) was measured directly from the ECMO circuit. Animals were placed on VA ECMO followed by an initial period of stabilization, after which they were subjected to graded hypoxia and recovery. Our results revealed that rSO(2)i and SVO(2) correlated only marginally with PbtO(2) (R(2)=0.32 and R(2)=0.26, respectively) while the correlation between rSO(2)i and SVO( 2) was significantly stronger (R(2)=0.59). Cerebral metabolites and rSO(2)i were significantly altered during attenuation of PbtO( 2), p<0.05). A subset of animals, following exposure to hypoxia, experienced markedly delayed recovery of both rSO(2)i and PbtO( 2) despite rapid normalization of SVO(2). Upon further analysis, these animals had significantly lower blood pressure (p=0.001), lower serum pH (p=0.01), and higher serum lactate (p=0.02). Additionally, in this subgroup, rSO(2)i correlated better with PbtO(2) (R(2)=0.76). These findings suggest that, in our ECMO model, rSO(2)i and SVO( 2) correlate reasonably well with each other, but not necessarily with brain PbtO(2) and that NIRS-derived rSO(2)i may more accurately reflect cerebral tissue hypoxia in sicker animals.

Cerebrovascular moyamoya disease in a 5-year-old girl who underwent interruption of the right common carotid artery in the neonatal period

The authors report on the case of a girl with cerebrovascular moyamoya disease born with severe respiratory failure caused by a congenital diaphragmatic hernia. Cardiopulmonary management included extracorporeal membrane oxygenation until the diaphragm defect was repaired. The right common carotid artery (CA) was interrupted and cannulated for extracorporeal membrane oxygenation. When she was 5 years of age, the patient experienced ischemic symptoms in her right extremities. Angiography revealed stenosis of the terminal portion of the internal CA (ICA) with the development of moyamoya vessels on the left side of the brain; the right ICA was supplied by extracranial anastomotic arteries. Indirect extracranial-intracranial bypass surgery was performed in the left hemisphere, and the hypoperfusion improved. The same change in the intracranial ICA with the development of moyamoya vessels occurred on her right side when she was 7 years old. Decreased cerebral blood flow occurred twice, and the moyamoya vessels developed to compensate for the cerebral ischemia. However, the occlusion of the extracranial common CA in infancy induced extracranial anastomosis rather than moyamoya vessel proliferation, and collateral circulation was formed at the lesion site. This finding indicates that neoangiogenesis requires both cerebral ischemia and growth factors derived from the lesion.

Systemic hyperthermia induces ischemic brain injury in neonatal mice with ligated carotid artery and jugular vein

Postnatal d 7 (p7) or p12 mice had their right carotid artery (CA) and jugular vein (JV) ligated to mimic veno-arterial (VA) access for extracorporeal membrane oxygenation (ECMO). At p9-11 (early) or p19-21 (late) mice were exposed to hyperthermia or normothermia followed by assessment of neuropathological injury score. In separate cohorts of mice, cerebral and peripheral blood flow (CBF, PBF) and cerebral ATP content was measured. Hyperthermia resulted in ischemic brain injury in 57% and 77% of mice subjected to early or late hyperthermia, respectively. Isolated CA+JV ligation induced minimal injury (score 0.47 +/- 0.34) in 2/8 mice from the late normothermia group. No cerebral injury was detected in mice subjected to early normothermia. In 3/19 shams (2/10 early, 1/9 late) hyperthermia induced a subtle (score, 0.6 +/- 0.27) injury in the ipsilateral to the site of surgery cortex. CBF and PBF increased in response to hyperthermia in all mice. The rise in CBF was significantly attenuated in the "ligated" versus intact hemisphere, which was associated with a profound depletion of ATP content. Systemic hyperthermia induces ischemic brain injury in mice with ligated CA+JV. We speculate that hyperthermia/fever can be a potential risk factor for brain injury in infants treated with VA ECMO.

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.

Improved results treating lung allograft failure with venovenous extracorporeal membrane oxygenation

BACKGROUND

Primary graft failure remains a significant source of mortality after lung transplantation. Extracorporeal membrane oxygenation (ECMO) provides treatment for affected recipients. We hypothesized that venovenous membrane oxygenation provides a safer alternative than venoarterial support for lung recipients suffering from primary graft failure.

METHODS

We conducted an analysis of 522 patients who underwent lung transplantation from April 1992 to July 2004. Twenty-three (4.5%) patients required membrane oxygenation secondary to primary graft failure unresponsive to conventional treatment. Of these recipients, 15 (65%) were treated with venoarterial, while 8 (35%) underwent venovenous membrane oxygenation.

RESULTS

Median days to initiation and duration of membrane oxygenation did not differ between groups. Eight of 15 patients (53%) from the venoarterial group were successfully weaned from life support, with one surviving greater than 45 days. This lone long-term survivor required retransplantation 4 days after initial transplant. In contrast, all venovenous patients were weaned from support, with 7 of 8 surviving greater than 30 days. The 30-day survival for venovenous recipients (88%) approximates that of all lung recipients at our center (94%, p = 0.42). Noted complications for ECMO patients included renal failure (n = 16), neurologic catastrophes (n = 8), sepsis (n = 5), and hemorrhage (n = 10). The venoarterial recipients suffered 30 of 39 total complications. Most of the complications for venovenous recipients involved renal failure, but by hospital discharge these patients demonstrated a mean creatinine of 0.9 mg/dL.

CONCLUSIONS

For lung recipients with primary graft failure, venovenous membrane oxygenation provides better outcomes, with fewer complications, than venoarterial membrane oxygenation.

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.

Inhaled nebulized nitrite is a hypoxia-sensitive NO-dependent selective pulmonary vasodilator

The blood anion nitrite contributes to hypoxic vasodilation through a heme-based, nitric oxide (NO)-generating reaction with deoxyhemoglobin and potentially other heme proteins. We hypothesized that this biochemical reaction could be harnessed for the treatment of neonatal pulmonary hypertension, an NO-deficient state characterized by pulmonary vasoconstriction, right-to-left shunt pathophysiology and systemic hypoxemia. To test this, we delivered inhaled sodium nitrite by aerosol to newborn lambs with hypoxic and normoxic pulmonary hypertension. Inhaled nitrite elicited a rapid and sustained reduction ( approximately 65%) in hypoxia-induced pulmonary hypertension, with a magnitude approaching that of the effects of 20 p.p.m. NO gas inhalation. This reduction was associated with the immediate appearance of NO in expiratory gas. Pulmonary vasodilation elicited by aerosolized nitrite was deoxyhemoglobin- and pH-dependent and was associated with increased blood levels of iron-nitrosyl-hemoglobin. Notably, from a therapeutic standpoint, short-term delivery of nitrite dissolved in saline through nebulization produced selective, sustained pulmonary vasodilation with no clinically significant increase in blood methemoglobin levels. These data support the concept that nitrite is a vasodilator acting through conversion to NO, a process coupled to hemoglobin deoxygenation and protonation, and evince a new, simple and inexpensive potential therapy for neonatal pulmonary hypertension.