Extracorporeal membrane oxygenation causes significant changes in intracranial pressure and carotid artery blood flow in newborn lambs

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.

Fetal brain morphometry on prenatal magnetic resonance imaging in congenital diaphragmatic hernia

BACKGROUND

Many infants with congenital diaphragmatic hernia (CDH) show brain abnormality on postnatal brain MRI related to severity of CDH, degree of lung hypoplasia, intrathoracic liver, right diaphragmatic hernia and large diaphragmatic defect. It is not known whether these factors affect brain growth in utero in CDH.

OBJECTIVE

To assess prenatal brain morphometry and abnormalities on fetal MR in congenital diaphragmatic hernia.

MATERIALS AND METHODS

We retrospectively reviewed 109 fetal MRIs in 63 fetuses with CDH from 2009 to 2014 (27 died before discharge, 36 survived to discharge). We compared brain injury and gestational-age-corrected z-scores of brain measurements between survivors and non-survivors. We assessed correlations between brain abnormalities and CDH severity.

RESULTS

Enlarged extraaxial space was the most common abnormality, frequently seen on fetal MRI at >28 weeks of gestation, similar in survivors versus non-survivors. Anteroposterior cerebellar vermis dimension at >28 weeks of gestation was smaller in non-survivors compared to survivors (P=.02) and positively correlated with observed/expected total fetal lung volume (P=.01). Transverse cerebellar diameter at >28 weeks of gestation was also positively correlated with observed/expected total fetal lung volume (P=.04). We did not identify maturational delay, abnormal parenchymal signal or intracranial hemorrhage on fetal MRI.

CONCLUSION

Enlarged extraaxial spaces in the third trimester was the most common abnormality on fetal MRI in congenital diaphragmatic hernia. Cerebellar dimensions on fetal MRI are associated with CDH severity. There was no major brain parenchymal injury on fetal MRI, even in the third trimester, in CDH survivors and non-survivors.

Pumpless arteriovenous extracorporeal membrane oxygenation: A novel mode of respiratory support in a lamb model of congenital diaphragmatic hernia

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is commonly required in neonates with congenital diaphragmatic hernia (CDH) complicated by pulmonary hypertension (PH). ECMO carries significant risk, and is contraindicated in the setting of extreme prematurity or intracranial hemorrhage. Pumpless arteriovenous ECMO (P-ECMO) may represent an alternative for respiratory support. The present study summarizes our initial experience with P-ECMO in a lamb model of CDH.

STUDY DESIGN

Surgical creation of CDH was performed at 65-75days' gestation. At term (135-145days), lambs were delivered into the P-ECMO circuit. Three animals were maintained on a low-heparin infusion protocol (target ACT 160-180) and three animals were maintained with no systemic heparinization.

RESULTS

Animals were supported by the circuit for 380.7 +/- 145.6h (range, 102-504h). Circuit flow rates ranged from 97 to 208ml/kg/min, with adequacy of organ perfusion demonstrated by stable serum lactate levels (3.0 +/- 1.7) and pH (7.4 +/- 0.3). Necropsy demonstrated no evidence of thrombogenic complications.

CONCLUSION

Pumpless extracorporeal membrane oxygenation achieved support of CDH model lambs for up to three weeks. This therapy has the potential to bridge neonates with decompensated respiratory failure to CDH repair with no requirement for systemic anticoagulation, and may be applicable to patients currently precluded from conventional ECMO support.

Regional Tissue Oximetry Reflects Changes in Arterial Flow in Porcine Chronic Heart Failure Treated With Venoarterial Extracorporeal Membrane Oxygenation

Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in treatment of decompensated heart failure. Our aim was to investigate its effects on regional perfusion and tissue oxygenation with respect to extracorporeal blood flow (EBF). In five swine, decompensated low-output chronic heart failure was induced by long-term rapid ventricular pacing. Subsequently, VA ECMO was introduced and left ventricular (LV) volume, aortic blood pressure, regional arterial flow and tissue oxygenation were continuously recorded at different levels of EBF. With increasing EBF from minimal to 5 l/min, mean arterial pressure increased from 47±22 to 84±12 mm Hg (P<0.001) and arterial blood flow increased in carotid artery from 211±72 to 479±58 ml/min (P<0.01) and in subclavian artery from 103±49 to 296±54 ml/min (P<0.001). Corresponding brain and brachial tissue oxygenation increased promptly from 57±6 to 74±3 % and from 37±6 to 77±6 %, respectively (both P<0.01). Presented results confirm that VA ECMO is a capable form of heart support. Regional arterial flow and tissue oxygenation suggest that partial circulatory support may be sufficient to supply brain and peripheral tissue by oxygen.

Correlation of MRI Brain Injury Findings with Neonatal Clinical Factors in Infants with Congenital Diaphragmatic Hernia

BACKGROUND AND PURPOSE

Infants with congenital diaphragmatic hernia are reported to have evidence of brain MR imaging abnormalities. Our study aimed to identify perinatal clinical factors in infants with congenital diaphragmatic hernia that are associated with evidence of brain injury on MR imaging performed before hospital discharge.

MATERIALS AND METHODS

MRIs performed before hospital discharge in infants with congenital diaphragmatic hernia were scored for brain injury by 2 pediatric neuroradiologists. Perinatal variables and clinical variables from the neonatal intensive care unit stay were analyzed for potential associations with brain MR imaging findings.

RESULTS

Fifty-three infants with congenital diaphragmatic hernia (31 boys) were included. At least 1 abnormality was seen on MR imaging in 32 infants (60%). The most common MR imaging findings were enlarged extra-axial spaces (36%), intraventricular hemorrhage (23%), ventriculomegaly (19%), white matter injury (17%), and cerebellar hemorrhage (17%). The MR imaging brain injury score was associated with extracorporeal membrane oxygenation (P = .0001), lack of oral feeding at discharge (P = .012), use of inotropes (P = .027), and gastrostomy tube placement before hospital discharge (P = .024). The MR imaging brain injury score was also associated with a large diaphragmatic defect size (P = .011).

CONCLUSIONS

Most infants with congenital diaphragmatic hernia have at least 1 abnormality identified on MR imaging of the brain performed before discharge. The main predictors of brain injury in this population are a requirement for extracorporeal membrane oxygenation, large diaphragmatic defect size, and lack of oral feeding at discharge.

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.

The long-term follow-up of patients with a congenital diaphragmatic hernia: a broad spectrum of morbidity

Congenital diaphragmatic hernia (CDH) is a life-threatening anomaly with a mortality rate of approximately 40-50%, depending on case selection. It has been suggested that new therapeutic modalities such as nitric oxide (NO), high frequency oxygenation (HFO) and extracorporal membrane oxygenation (ECMO) might decrease mortality associated with pulmonary hypertension and the sequelae of artificial ventilation. When these new therapies indeed prove to be beneficial, a larger number of children with severe forms of CDH might survive, resulting in an increase of CDH-associated complications and/or consequences. In follow-up studies of infants born with CDH, many complications including pulmonary damage, cardiovascular disease, gastro-intestinal disease, failure to thrive, neurocognitive defects and musculoskeletal abnormalities have been described. Long-term pulmonary morbidity in CDH consists of obstructive and restrictive lung function impairments due to altered lung structure and prolonged ventilatory support. CDH has also been associated with persistent pulmonary vascular abnormalities, resulting in pulmonary hypertension in the neonatal period. Long-term consequences of pulmonary hypertension are unknown. Gastro-esophageal reflux disease (GERD) is also an important contributor to overall morbidity, although the underlying mechanism has not been fully understood yet. In adult CDH survivors incidence of esophagitis is high and even Barrett's esophagus may ensue. Yet, in many CDH patients a clinical history compatible with GERD seems to be lacking, which may result in missing patients with pathologic reflux disease. Prolonged unrecognized GERD may eventually result in failure to thrive. This has been found in many young CDH patients, which may also be caused by insufficient intake due to oral aversion and increased caloric requirements due to pulmonary morbidity. Neurological outcome is determined by an increased risk of perinatal and neonatal hypoxemia in the first days of life of CDH patients. In patients treated with ECMO, the incidence of neurological deficits is even higher, probably reflecting more severe hypoxemia and the risk of ECMO associated complications. Many studies have addressed the substantial impact of the health problems described above, on the overall well-being of CDH patients, but most of them concentrate on the first years after repair and only a few studies focus on the health-related quality of life in CDH patients. Considering the scattered data indicating substantial morbidity in long-term survivors of CDH, follow-up studies that systematically assess long-term sequelae are mandatory. Based on such studies a more focused approach for routine follow-up programs may be established.

Venoarterial extracorporeal membrane oxygenation impairs basal nitric oxide production in cerebral arteries of newborn lambs

OBJECTIVE

Based on previous studies in our laboratory showing that exposure of newborn lambs to venoarterial extracorporeal membrane oxygenation (ECMO) alters cerebral blood flow autoregulation, we postulated that this altered vascular reactivity is mediated through changes in endothelial function caused by the pumping systems used in venoarterial ECMO. We tested that hypothesis in this study.

DESIGN

Prospective, controlled, laboratory trial.

SETTING

Animal research laboratory.

SUBJECTS

Two groups of newborn lambs.

INTERVENTIONS

One group of animals was exposed to venoarterial ECMO (n = 6) and another group of control animals (n = 5) was maintained under similar conditions for 2 hrs on the ventilator without ECMO.

MEASUREMENTS AND MAIN RESULTS

Third-order branches of the middle cerebral arteries (140-300 microm diameter) were isolated from animals at the end of the experiment, mounted on glass cannulae in an arteriograph, and superfused with Krebs-Ringer buffer. Decrease in the diameter of the arteries induced by exposure of the vessels to nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (200 micromol/L) for 30 mins was significantly less (p <.05) in arteries from lambs exposed to ECMO compared with control animals. There were no significant differences between the two groups in myogenic response or in the contractile activity of the arteries to increasing concentrations of serotonin.

CONCLUSIONS

These results demonstrate that 2 hrs of exposure of newborn lambs to venoarterial ECMO leads to a decrease in basal production of nitric oxide in cerebral arteries, and suggest that venoarterial ECMO selectively impairs cerebral arterial endothelial function.

Regional blood flow distribution from the proximal arterial cannula during veno-arterial extracorporeal membrane oxygenation in neonatal dog

Extracorporeal membrane oxygenation (ECMO) is frequently used for treatment of patients with severe hypoxemia due to life-threatening respiratory failure. Due to this hypoxemia, the myocardium of these patients is insufficiently provided with oxygen, and consequently their cardiac function commonly deteriorates. But veno-arterial (V-A) ECMO provides oxygenated blood to the coronary arteries from ECMO circuit insufficiently. To increase the coronary blood flow distributed from ECMO, we placed the arterial cannula 1 cm above the aortic valve and evaluated the regional blood from the proximal arterial cannula in comparison with the distal cannula. Eight neonatal dogs weighting 1.8-2.5 kg were supported by V-A ECMO. The regional blood flow from the arterial cannula was measured by injection of colored microspheres into ECMO circuit. The site of the arterial cannula was changed under fluoroscopy. The bypass flow was maintained at either 50 or 100 ml/min/kg. We found that the coronary blood flow distributed from the proximal arterial cannula was significantly higher than that from the distal cannula. The proximal arterial cannula appears necessary to provide sufficient oxygenated blood to the coronary circulation during V-A ECMO. Therefore, it is expected that the increased cardiac function may improved, and that the survival rate of the patients with retarded cardiac function due to severe hypoxemia may increase by proximal placement of the arterial cannula during V-A ECMO.

The use of cephalad cannulae to monitor jugular venous oxygen content during extracorporeal membrane oxygenation

BACKGROUND: When used during extracorporeal membrane oxygenation (ECMO), jugular venous bulb catheters, known as cephalad cannulae, increase venous drainage, augment circuit flow and decompress cerebral venous pressure. Optimized cerebral oxygen delivery during ECMO may contribute to a reduction in neurological morbidity. This study describes the use of cephalad cannulae and identifies rudimentary data for jugular venous oxygen saturation (JVO2) and arterial to jugular venous oxygen saturation difference (AVDO2) in this patient population. RESULTS: Patients on venoarterial (VA) ECMO displayed higher JVO2 (P < 0.01) and lower AVDO2 (P = 0.01) than patients on venovenous (VV) ECMO (P < 0.01). During VV ECMO, JVO2 was higher and AVDO2 lower when systemic pH was < 7.35 rather than > 7.4 (P = 0.01). During VA ECMO, similar differences in AVDO2 but not in JVO2 were observed at different pH levels (P = 0.01). CONCLUSIONS: Jugular venous saturation and AVDO2 were influenced by systemic pH, ECMO type and patient age. These data provide the foundation for normative values of JVO2 and AVDO2 in neonates and children treated with ECMO.

The influence of extracorporeal membrane oxygenation on cerebral oxygenation and hemodynamics in normoxemic and hypoxemic piglets

The objective of this study was to compare the effect of extracorporeal membrane oxygenation (ECMO) on cerebral oxygenation and hemodynamics in normoxemic and hypoxemic piglets. Six hypoxemic and six normoxemic piglets were put on venoarterial ECMO after cannulation of the right common carotid artery and external jugular vein with careful priming to avoid hemodilution. Changes in cerebral concentrations of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), (oxidized-reduced) cytochrome aa3 (cCyt.aa3), and blood volume (CBV) were continuously measured by near infrared spectrophotometry. Heart rate, arterial O2 saturation (SaO2), arterial blood pressure, pulsatility ratio of systemic circulation (calculated as systolic-diastolic/mean arterial blood pressure), central venous pressure, intracranial pressure, and left common carotid artery blood flow (LCaBF) were simultaneously measured. We found that the cannulation procedure resulted in increased CBV, cHHb, and LCaBF in both groups. At 60 and 120 min after starting ECMO, the values of cO2Hb, CBV, and LCaBF in both groups were significantly higher than precannulation values, while the pulsatility ratio decreased. In the hypoxemic groups cHHb decreased and SaO2 increased as well. No significant changes of other variables were found. Between hypoxemic and normoxemic groups no significant differences in the response of CBV and LCaBF at 60 and 120 min were found. We conclude that in piglets cannulation for ECMO resulted in cerebral venous congestion and compensated increase in LCaBF. After starting ECMO, the cerebral O2 supply increased due to increased arterial O2 content. It was accompanied by similar increase of CBV in both groups, probably as a result of hyperperfusion, which seems to be related to the ECMO procedure itself.

The influence of arterial carbon dioxide on cerebral oxygenation and haemodynamics during ECMO in normoxaemic and hypoxaemic piglets

OBJECTIVE

To investigate the cerebrovascular response to changes in arterial CO2 tension during extracorporeal membrane oxygenation (ECMO) in normoxaemic and hypoxaemic piglets.

METHODS

Four groups of six anaesthetized, paralysed and mechanically ventilated piglets: group 1-normoxaemia without ECMO, group 2-ECMO after normoxaemia, group 3-hypoxaemia without ECMO, and group 4-ECMO after hypoxaemia, were exposed successively to hypercapnia and hypocapnia. Changes in cerebral concentrations of oxyhaemoglobin (cO2Hb), deoxyhaemoglobin (cHHb), (oxidized-reduced) cytochrome aa3 (cCyt.aa3) and blood volume (CBV) were continuously measured using near infrared spectrophotometry. Heart rate, arterial O2 saturation, arterial blood pressure, central venous pressure, intracranial pressure (ICP) and left common carotid artery blood flow (LCaBF) were measured simultaneously.

RESULTS

Hypercapnia resulted in increased CBV, cO2Hb and ICP in all groups, while cHHb was decreased. No changes in LCaBF were found. Hypocapnia resulted in decreased cO2Hb and increased cHHb except in group 3. LCaBF decreased in all groups except group 2. CBV decreased only in groups 2 and 4. No effect on ICP was observed in any of the groups. The other variables showed no important changes either during hypercapnia or hypocapnia. ECMO after hypoxaemia resulted in a greater response of cO2Hb and cO2Hb and cHHb during hypocapnia. The effect of hypercapnia on CBV while on ECMO was greater than without ECMO.

CONCLUSION

Since cerebrovascular reactivity to CO2 remains intact during ECMO in piglets, it is important to keep arterial CO2 tension stable and in normal range during clinical ECMO.

Neurocognitive outcome for neonates treated with extracorporeal membrane oxygenation: are infants with congenital diaphragmatic hernia different?

The neurocognitive outcome for infants with congenital diaphragmatic hernia treated with extracorporeal membrane oxygenation (ECMO) is compared with that of neonates treated with ECMO for other diagnoses. The mean age at the time of the latest assessment (for the 51 survivors with adequate follow-up) was 31 months. The neurological outcomes did not differ significantly. However, the cognitive outcome for infants with congenital diaphragmatic hernia was significantly poorer than for those without it. This was particularly true if the infant with congenital diaphragmatic hernia was a boy and his mother had limited formal education.

Neuroimaging of brain injury in neonates treated with extracorporeal membrane oxygenation: lessons learned from serial examinations

The head ultrasound (US) is used extensively at most extracorporeal membrane oxygenation (ECMO) centers to screen for intracranial pathology in the ECMO candidate. Daily head US examinations are obtained in patients on ECMO to detect the emergence of intracranial hemorrhage (ICH). The authors asked whether these serial studies could be correlated with more definitive diagnostic studies, such as computed tomography (CT) and magnetic resonance imaging (MRI) scans, autopsy data, or the long-term neurodevelopmental status, to discern the predictive value of these daily examinations. Seventy-four consecutively treated neonates with reversible respiratory failure refractory to conventional support met institutional criteria for placement on ECMO. In addition to a pre-ECMO US, daily real-time portable head US images were evaluated for changes in echotexture, ventricular configuration, and extraaxial fluid. Follow-up CT and MRI scans were evaluated for the presence of hemorrhagic or ischemic lesions. Autopsy data were obtained from nonsurvivors. Survivors were examined by a neurodevelopmental specialist at regular intervals and classified as normal or delayed for chronological age. In this series of 74 patients, CT/MRI scanning and autopsy data demonstrated structural injury in 19 patients; there were 16 ischemic infarctions and three hemorrhages. The incidence of hemorrhage in this series was considerably lower than that previously reported. Ten of the 19 patients had serial head US findings demonstrating a progression from focal increases in echotexture to diffuse effacement of cerebral architecture. In the remaining nine, serial head US examinations did not show injury. An additional 10 children had a clear delay in neurological development despite no evidence of anatomic injury on serial head US examinations or CT/MRI scanning.(ABSTRACT TRUNCATED AT 250 WORDS)

Proximal and distal cannulation of the internal jugular vein for ECMO in a primate

Extracorporeal membrane oxygenation (ECMO) is lifesaving for infants with severe respiratory distress but is complicated by severe intracranial hemorrhage in 10% to 30% of patients. Intracranial venous hypertension, as a result of ligation of the internal jugular vein (IJV), has been hypothesized as a contributing factor to cerebral edema and subsequent hemorrhage. Accessory cephalad IJV cannulation may serve as a means of additional venous drainage to the pump as well as protection against intracranial venous hypertension. Proximal and distal cannulation of the IJV were studied in a primate model. The parameters monitored included sagittal sinus, right and left ventricular pressures as well as venous pressure in the ECMO circuit. The cephalad venous cannula was clamped and unclamped at 30-minute intervals. There was no significant difference in sagittal sinus or intracranial pressures during periods of cephalad cannula clamping or unclamping. Venous return was augmented when the cephalad cannula was unclamped. Cephalad cannulation has no demonstrable protective effect on intracranial, subarachnoid or venous pressures but does improve venous return to the ECMO circuit. It is concluded that cephalad venous cannulation is not necessary in all cases and should be reserved for those patients requiring additional venous drainage to support pump flow.

Congenital diaphragmatic hernia, extracorporeal membrane oxygenation, and death: a spectrum of etiologies

Extracorporeal Life Support Organization (ELSO) registry data show increased mortality in congenital diaphragmatic hernia (CDH) infants compared with other extracorporeal membrane oxygenation (ECMO) indications. To test the hypothesis that death might be related to various clinical parameters, retrospective data collection was solicited on 175 ECMO-related CDH deaths from 41 American ECMO centers (ELSO Registry 1980 through 1989). Data capture forms were received on 100 of 175 infants representing 29 of 41 centers. After review of all available material, a predominant cause of death was assigned. Other diagnoses were given secondary status. We analyzed arterial blood gas values at 6, 3, and 1 hour pre-ECMO, as well as at the time of highest recorded PO2 (preductal and postductal) and lowest recorded PCO2, and correlated these findings with predominant cause of death. The relationship between individual variables and cause of death was assessed by t test. Multivariate analysis was performed by using a stepwise discriminate procedure. The most common predominant causes of death were brain death (29%), pulmonary hypertension (25%), and pulmonary hypoplasia (17%). Correlation of arterial blood gas values at 6, 3, and 1 hour pre-ECMO with predominant causes of death established the following statistically significant associations (P less than .05): (1) pulmonary hypoplasia and low PO2 at 6 hours pre-ECMO; (2) brain death and low pH at 1 hour pre-ECMO; and (3) pulmonary hypertension and high HCO3- at 1 hour pre-ECMO.(ABSTRACT TRUNCATED AT 250 WORDS)