Use of point-of-care ultrasound (POCUS) to monitor neonatal and pediatric extracorporeal life support

Extracorporeal membrane oxygenation (ECMO) is an invasive life support technique that requires a blood pump, an artificial membrane lung, and vascular cannulae to drain de-oxygenated blood, remove carbon dioxide, oxygenate, and return it to the patient. ECMO is generally used to provide advanced and prolonged cardiopulmonary support in patients with refractory acute cardiac and/or respiratory failure. After its first use in 1975 to manage a severe form of meconium aspiration syndrome with resultant pulmonary hypertension, the following years were dominated by the use of ECMO to manage neonatal respiratory failure and limited to a few centers across the world. In the 1990s, evidence for neonatal respiratory ECMO support increased; however, the number of cases began to decline with the use of newer pharmacologic therapies (e.g., inhaled nitric oxide, exogenous surfactant, and high-frequency oscillatory ventilation). On the contrary, pediatric ECMO sustained steady growth. Combined advances in ECMO technology and bedside medical management have improved general outcomes, although ECMO-related complications remain challenging. Point-of-care ultrasound (POCUS) is an essential tool to monitor all phases of neonatal and pediatric ECMO: evaluation of ECMO candidacy, ultrasound-guided ECMO cannulation, daily evaluation of heart and lung function and brain perfusion, detection and management of major complications, and weaning from ECMO support.  Conclusion: Based on these considerations and on the lack of specific guidelines for the use of POCUS in the neonatal and pediatric ECMO setting, the aim of this paper is to provide a systematic overview for the application of POCUS during ECMO support in these populations. What is Known: • Extracorporeal membrane oxygenation (ECMO) provides advanced cardiopulmonary support for patients with refractory acute cardiac and/or respiratory failure and requires appropriate monitoring. • Point-of-care ultrasound (POCUS) is an accessible and adaptable tool to assess neonatal and pediatric cardiac and/or respiratory failure at bedside. What is New: • In this review, we discussed the use of POCUS to monitor and manage at bedside neonatal and pediatric patients supported with ECMO. • We explored the potential use of POCUS during all phases of ECMO support: pre-ECMO assessment, ECMO candidacy evaluation, daily evaluation of heart, lung and brain function, detection and troubleshooting of major complications, and weaning from ECMO support.

Ultrasound-guided lung lavage for life-threatening bronchial obstruction due to meconium plug

We present a case of life-threatening airway obstruction caused by meconium aspiration, a condition with significant neonatal mortality and morbidity. Lung ultrasound detected the obstruction and helped in the clinical management allowing to perform a quick and selective bronchoalveolar lavage with diluted surfactant.

Routine application of lung ultrasonography in the neonatal intensive care unit

The aim of this study was to study the features of lung ultrasonography (LUS) in lung disease and to evaluate the usefulness of LUS in the neonatal intensive care unit (NICU).All of 3405 neonates included in this study underwent an LUS examination. Diagnoses were based on medical history, clinical manifestation, laboratory examination, and signs on chest radiography (CR) and/or computed tomography (CT). A single expert physician performed all LUS examinations.There were 2658 cases (78.9%) with lung disease and 747 cases (21.9%) without lung disease. The main signs of neonates with lung disease on LUS were as follows: absence of A-lines, pleural-line abnormalities, interstitial syndrome, lung consolidation, air bronchograms, pulmonary edema, and lung pulse. These abnormal signs were reduced or eliminated on LUS as patient conditions improved. There were 81 cases that could not be diagnosed as lung disease by CR but were discovered as pneumonia, respiratory distress syndrome (RDS), or transient tachypnea of newborn (TTN) on LUS. Likewise, 23 cases misdiagnosed as RDS by CR were diagnosed as TTN on LUS. Among 212 cases of long-term oxygen dependence (LTOD) that failed to yield signs of pulmonary edema and lung consolidation on CR, 103 cases showed abnormal signs on LUS. Among 747 cases without lung disease, B-lines of 713 neonates (95.4%) could be found within 3 days after birth, and 256 neonates (34.3%) could be observed from 3 days to 1 week after birth. B-lines of 19 cases could be detected from 1 to 2 weeks after birth. The longest time at which B-lines could still be observed was 19 days after birth.LUS has clinical value for the diagnosis of lung disease and the discrimination of causes of LTOP in premature infants, particularly for the diagnosis and identification of RDS and TTN. Moreover, LUS has additional advantages, including its lack of radiation exposure and its ability to noninvasively monitor treatment progress. Therefore, LUS should be routinely used in the NICU.

Lung ultrasonography to diagnose meconium aspiration syndrome of the newborn

Objective To investigate the diagnostic value of lung ultrasonography for neonatal meconium aspiration syndrome (MAS). Methods This prospective observational study enrolled patients diagnosed with MAS based on medical history, clinical manifestations and chest X-ray and control newborns without MAS. During ultrasonography, each lung was divided into three regions (front, lateral, and back), using anterior and posterior axillary lines as the boundary. While scanning each region of the lungs, the hand piece was perpendicular or parallel to the ribs. Results This study enrolled 117 newborns with MAS and 100 controls. The main lung ultrasonographic findings in patients with MAS were: (i) pulmonary consolidation with air bronchogram was found in all patients; (ii) pleural line anomalies and the disappearance of the A-line was found in all patients; (iii) atelectasis was found in 19 (16.2%) severe cases, who demonstrated severe massive atelectasis and visible lung pulse; (iv) pleural effusion was found in 16 patients (13.7%); and (v) alveolar-interstitial syndrome or B-line in the non-consolidation area was found in all patients with MAS. Conclusion Ultrasonography can be used routinely to diagnose MAS in an accurate, reliable, convenient, and non-invasive manner.

Lung Ultrasonography to Diagnose Transient Tachypnea of the Newborn

BACKGROUND

This study explored the sensitivity and specificity of ultrasound for diagnosing transient tachypnea of the newborn (TTN).

METHODS

Ultrasound was performed by one export. Patients were placed in a supine, lateral recumbent, or prone position. The probe was placed perpendicular or parallel to the ribs, and each region of the lung was scanned. The scan results were compared with conventional chest radiographic results.

RESULTS

A total of 1,358 infants were included in this study. We identified 412 cases without pulmonary diseases, 228 TTN cases, 358 respiratory distress syndrome (RDS) cases, 85 meconium aspiration syndrome (MAS) cases, 215 infectious pneumonia cases, and 60 other cases. The primary ultrasonic characteristic of TTN was pulmonary edema. "White lung" or a "compact B-line" were only observed in severe cases, whereas TTN primarily presented as pulmonary interstitial syndrome or "double lung point." Furthermore, double lung point could appear during the recovery period of severe TTN or RDS, MAS, and pneumonia. Lung consolidation with air bronchograms was not observed in TTN patients. The results showed that white lung or a compact B-line exhibited a sensitivity of 33.8% and a specificity of 91.3% in diagnosing TTN, whereas double lung point exhibited a sensitivity of 45.6% and a specificity of 94.8% in diagnosing severe TTN.

CONCLUSIONS

Pulmonary edema, alveolar-interstitial syndrome, double lung point, white lung, and compact B-line are the primary ultrasound characteristics of TTN. Ultrasonic diagnosis of TTN based on these findings is accurate and reliable. TTN can be ruled out in the presence of lung consolidation with air bronchograms.

Prolonged resuscitation in a newborn recovering from meconium aspiration syndrome

A complication during the course of meconium aspiration syndrome associated with persistent pulmonary hypertension in a newborn results in hypotension, bradycardia, and desaturation. The dilemmas and critical actions during the resuscitation are presented.

Surfactant lavage and replacement in meconium aspiration syndrome with pulmonary hemorrhage

We reported two case studies of meconium aspiration syndrome (MAS) with pulmonary hemorrhage in which we applied surfactant lavage and replacement. Surfactant lavage and replacement of MAS with pulmonary hemorrhage appears to be effective and safe adjunctive therapy. The relatively small replacement doses of surfactant required may be attributed to surfactant lavage followed by surfactant replacement. We suggest that surfactant lavage and replacement of MAS with pulmonary hemorrhage should be further investigated by a randomized controlled trial.

Surfactant tracheobronchial lavage for the management of a rabbit model of meconium aspiration syndrome

We evaluated the effect of tracheobronchial lavage with diluted surfactant solution (bovine lipid extract surfactant, bLES) in a rabbit model of meconium aspiration. All animals were anaesthetized, tracheotomized and given 3-4 ml/kg of 25% slurry of human meconium into the endotracheal tube and mechanically ventilated for 1 h. The animals were then randomly assigned to surfactant lavage (n = 12) with 15 ml/kg of diluted surfactant at a concentration of 5.4 mg phospholipid/ml administered in aliquots of 2 ml; or simple endotracheal suction (control n = 12) when the oxygenation index (OI) was >/=15. Changes in the arterial blood gases and the histomorphological and radiological appearances of the lungs were recorded. The OI and arterial/alveolar oxygen tension (a/A PO2) of the surfactant lavage group improved significantly at 5 min post-treatment, and these improvements were observed throughout the ensuing 4 h of ventilation. There was significantly more solid content recovered by surfactant lavage compared with the control group (p = 0.0001). Radiologically, the post-treatment air space opacification scores of the lavage group were significantly lower compared with the control (p = 0.002). The post-treatment radiographs of the lavage-treated rabbits were rated by the radiologist, who was blinded to the treatment groups, as much improved in 5 and improved in 4, whereas the control rabbits were rated as much worse in 3 and worse in 4. Histological examination showed the lungs of the lavaged rabbits had significantly more normal airway (p < 0.0001), more fields showing completely normal airspace (p = 0.0001) and less fields showing severe overdistension with meconium (p = 0.0005). We concluded that lavage with diluted surfactant solution effectively washed out the meconium, improved gases exchanges, and improved the histological and radiological appearances in the rabbit model of MAS.

Meconium peritonitis in utero

To clarify the relationship between clinical features in utero and postnatal prognosis, 20 fetuses who underwent ultrasonic (US) evaluation for meconium peritonitis (MP) over a 17-year period were reviewed. According to final US findings in utero, patients were classified into three types. Type I (massive meconium ascites) was noted is 5 cases, type II (giant pseudocyst) in 4, and the other 11 were classified as type III (calcification and/or small pseudocyst). Abdominal calcifications were identified in only 5 cases (2 type I, 1 type II, 2 type III). Seven fetuses who had associated polyhydramnios (1 Type I, 1 Type II, 2 Type III) and fetal hydrops (3 Type II) were delivered before 36 weeks' gestation. Cardiopulmonary resuscitation at birth was required in 9 cases (5 type I, 4 type II) who underwent abdominal drainage before delivery and/or immediately after birth. Although dilatation of the intestine was identified in 10 fetuses (2 type II, 8 Type III), 18 had intestinal atresia and 2 had fecal obstruction of the distal ileum. Four infants (2 type I, 1 type II, 1 type III) died of respiratory failure and postoperative complications. These results indicated that careful fetal US may be useful for perinatal management of MP.

Delayed adaptation of the pulmonary hemodynamics in infants with mild to moderate meconium aspiration syndrome

Early postnatal pulmonary hemodynamic changes were investigated with Doppler echocardiography in 17 infants with mild or moderate meconium aspiration syndrome (MAS) and 16 healthy infants in a control group. The results indicate that the physiologic adaptation of the pulmonary hemodynamics is delayed in mild and moderate forms of MAS. Thus infants with clinical evidence of MAS need careful cardiovascular monitoring during postnatal circulatory transition.

Meconium aspiration syndrome complicated by massive intravascular thrombosis

Fetal aspiration of meconium in amniotic fluid during fetal distress by newborn infants can induce the meconium aspiration syndrome (MAS), a form of neonatal respiratory distress. Should this event occur, admission to a Neonatal Intensive Care Unit and vigorous airway management and monitoring are required. We present a term gestation resulting in MAS complicated by a massive intravascular thrombosis. Despite airway management considered appropriate, the infant developed respiratory distress a few hours after birth and died 5 days later. Postmortem examination showed a diffuse alveolar damage of the lungs with alveoli filled with meconium and amniotic epithelial cells as well as disseminated thrombi in the pulmonary vascular tree, portal system, suprahepatic veins, and peripheral arterial vascular tree.

Echocardiographic prediction of neonatal ECMO outcome

Cardiopulmonary physiology was assessed by Doppler echocardiography in neonates undergoing pre-ECMO evaluation for meconium aspiration syndrome, congenital diaphragmatic hernia, persistent fetal circulation, and sepsis, from March 1987 through July 1992 (n = 136). Percent survival by diagnosis was: meconium aspiration syndrome, 86%; persistent fetal circulation, 68%; congenital diaphragmatic hernia, 63%; sepsis, 33%. Survival odds by diagnosis predicted a better outcome for meconium aspiration syndrome than for congenital diaphragmatic hernia and sepsis, and a better outcome for persistent fetal circulation than for sepsis. Percent survival for right-to-left patent ductus arteriosus flow (PDA) was 56%; other patent ductus arteriosus flow was 84%. In multivariate analysis, percent survival in congenital diaphragmatic hernia and persistent fetal circulation patients with right-to-left PDA flow suggested a worse outcome (% survival right-to-left vs other: congenital diaphragmatic hernia, 13% vs 70%; persistent fetal circulation, 25% vs 85%), whereas percent survival did not appear to suggest the same in meconium aspiration syndrome or sepsis patients. Similar analysis in non-ECMO patients suggested a worse outcome with right-to-left PDA flow in patients with meconium aspiration syndrome and congenital diaphragmatic hernia. Right-to-left PDA flow, sepsis, and congenital diaphragmatic hernia were associated with a poorer ECMO outcome. Initial assessment of PDA flow helps predict ECMO outcome.

The posterior fontanelle: a neglected acoustic window

The additional information, obtained when using the posterior fontanelle routinely as the second acoustic window, is illustrated in four infants. Three of them are full-term infants with hypoxic ischaemic encephalopathy. In newborn infants, who are still too unstable to be transported to the magnetic resonance unit, extensive damage in the occipital subcortical white matter and/or cortex can be visualised by performing cranial ultrasound through the posterior fontanelle.

Management of meconium aspiration syndrome by tracheobronchial lavage and replacement of Surfactant-TA

Meconium aspiration syndrome creates mechanical airway obstruction with air trapping and atelectasis. Tracheobronchial saline lavage to dislodge meconium may precipitate respiratory distress, a wet lung appearance and respiratory failure. Two case studies are reported in which meconium aspiration resulted in mechanical obstruction and displacement of surfactant and in whom tracheobronchial saline lavage and artificial surfactant replacement reversed respiratory failure.

A radiologic update on medical diseases of the newborn chest

This paper reviews the common spectrum of medical diseases of the neonatal chest. Emphasis is on radiographic changes that have been produced by the introduction of new therapeutic maneuvers, particularly the use of artificial surfactant in treating hyaline membrane disease and the survival of profoundly premature newborns (less than 650 g). A discussion of meconium aspiration syndrome, neonatal pneumonia, transient tachypnea of the newborn, congenital lymphangiectasia, and congenital heart disease is also included. The effects on the neonatal chest radiograph of extracorporeal membrane oxygenation and high-frequency ventilation are also mentioned.

Mechanisms of change in cardiac performance in infants undergoing extracorporeal membrane oxygenation

OBJECTIVE

To determine whether changes in cardiac performance observed in infants early during extracorporeal membrane oxygenation are due to the underlying disease process, the partial bypass procedure, changes in cardiac loading conditions, or due to a direct myocardial effect of hypoxia-reoxygenation.

DESIGN

Consecutive case series.

PATIENTS

Infants with meconium aspiration syndrome were studied at the end of their extracorporeal membrane oxygenation course (veno-arterial, n = 12; veno-venous, n = 8), after lung compliance and pulmonary arterial pressure returned toward normal and they were ready to have extracorporeal membrane oxygenation discontinued.

INTERVENTIONS

Heart rate, mean arterial blood pressure, and load-dependent indices, and a load-independent index of cardiac performance were measured at increasing bypass flow rates (25, 50, 75, 100, 125 mL/kg/min).

MEASUREMENTS AND MAIN RESULTS

Heart rate, mean arterial blood pressure, and load-dependent indices of cardiac performance (left ventricular shortening fraction and stroke volume) were normal at 25 mL/kg/min bypass flow rate and did not change significantly with increasing bypass flow rates. The load-independent index of performance was within the normal range for infants and did not change significantly with increasing bypass flow rates.

CONCLUSIONS

The previously described decreases in cardiac performance during extracorporeal membrane oxygenation are not due to the underlying disease process or the bypass procedure but are due to changes in loading conditions during partial bypass.

Early changes in the neonatal circulatory transition

To define the course of neonatal circulatory transition and to identify clinically relevant echocardiographic measurements in the diagnosis of persistent pulmonary hypertension, we prospectively studied 32 healthy term infants from 30 minutes to 24 hours after birth with color and quantitative Doppler echocardiography on the first day of life, and compared them with 33 term infants supported by mechanical ventilation for respiratory failure. Color Doppler imaging included measurements of cardiac output, left pulmonary artery flow, aortopulmonary pressure difference, ductal flow, left-to-right color-flow jet area of the ductus arteriosus, and ductal flow characteristics. In healthy infants the majority of measurable changes in cardiopulmonary hemodynamics had occurred by 8 hours after birth, although some degree of right-to-left ductal shunting was found up to 12 hours after birth. In the infants with respiratory failure, ductal flow and maximum aortopulmonary pressure difference measurements at 8, 12, and 24 hours showed a significant delay in ductal closure and a high incidence of persistent pulmonary hypertension, which correlated well with the severity of their respiratory failure. Factors such as aortopulmonary pressure difference, prolonged right-to-left shunting with decreased left pulmonary artery flow, and failure to develop a left-to-right ductal color-flow jet were found to be practical markers for assessing the course of neonatal circulatory transition in sick term infants.

Left ventricular performance in neonates on extracorporeal membrane oxygenation

The evaluation of left ventricular systolic performance in infants undergoing extracorporeal membrane oxygenation (ECMO) using traditional ejection-phase indices is hampered by significant alterations in preload and afterload. Therefore, a load-independent index, which relates heart-rate-corrected mean velocity of circumferential fiber shortening (VCFc) to afterload, measured as end-systolic wall stress (ESS), was used to assess left ventricular function in 18 term neonates undergoing ECMO. The mean age at the onset of ECMO was 75.5 h and the duration of therapy was 171 +/- 106 h. Left ventricular performance was highest before the onset of ECMO (VCFc = 1.65 +/- 0.49 circ/s) and decreased toward normal during (1.38 +/- 0.33 circ/s) and following ECMO (1.29 +/- 0.16 circ/s). Initially, nine of 17 (53%) patients had enhanced performance for the degree of afterload but in only 16 of 48 (33%) studies during ECMO and none following ECMO was VCFc elevated beyond the normal range predicted for ESS. These changes in left ventricular performance may be the result of variations in exogenous, as well as endogenous, catecholamines rather than intrinsic alterations in myocardial contractility. It is concluded that the VCFc/ESS relation permits a meaningful assessment of ventricular performance in critically ill neonates undergoing ECMO.

Meconium aspiration syndrome--unusual features

A term infant with the meconium aspiration syndrome (MAS) is described. He had the typical clinical course of the disease despite appearing well nourished, and with good Apgar scores. At 5 months of age, he continued to do well with no sequelae. The reason for the initial passage of meconium in-utero remained speculative. The fact that the disease is preventable is emphasised.

Possible causes linking asphyxia, thick meconium and respiratory distress

The cause of fetal distress and neonatal respiratory distress (RD) in association with meconium-stained liquor is not always clear. To clarify this, a prospective study was undertaken in a tertiary referral maternity hospital for 1 year. In all infants born after meconium-stained liquor who developed RD, evidence was sought for 1) fetal distress (from the cardiotocograph (CTG), the cord blood pH, the Apgar score and the asphyxial complications in the neonate) 2) causes of fetal distress (including maternal risk factors, fetal infection and fetal malnutrition) 3) causes of respiratory distress (including meconium aspiration syndrome (MAS), persistent pulmonary hypertension of the newborn (PPHN) and infection). Of 4,026 livebirths, 717 (17.8%) had meconium-stained liquor and 44 term and 5 preterm infants developed RD. In the 44 term infants, there was frequent evidence of fetal distress possibly caused by previously unrecognized factors such as fetal malnutrition with reduced neonatal skinfold thickness in 35% triceps and 41% subscapular measurements, and histological chorioamnionitis (CA) in 74%. The cause for respiratory distress was identified in only 48% of infants, and included clinical evidence of PPHN (41%), MAS (16%) and infection (2%). However in preterm infants, 80% had definite or suspected infection. The findings indicate that fetal distress is common in infants who develop respiratory distress after meconium-stained liquor. A role for histological CA and reduced nutrition in the fetus, as factors contributing to the vulnerability of the term infant to intrapartum fetal distress, is suggested.

Carotid artery reconstruction following extracorporeal membrane oxygenation

Right hemispheric brain injury has been noted in surviving infants treated with venoarterial extracorporeal membrane oxygenation (ECMO). This phenomenon may be secondary to permanent ligation of the right carotid artery. At our institution, conventional ventilatory therapy failed in five neonates with respiratory insufficiency, and they were treated successfully with ECMO. In four of the five neonates, the right carotid artery was reconstructed at the time of decannulation. At discharge, all newborns with carotid artery repair showed no signs of unilateral brain injury and had excellent antegrade flow in the right carotid artery as assessed by both duplex and transcranial Doppler ultrasound scanning. Carotid artery reconstruction after ECMO is a technically simple procedure that may reduce the incidence of right hemispheric brain injury and long-term consequences of marginal cerebral perfusion.

[Relationship of chest roentgenographic features and outcome in meconium aspiration syndrome]

Aspiration of meconium may produce respiratory distress of various severity and outcome. It is the purpose of this study to evaluate the relationship between roentgenographic feature of initial chest roentgenogram (less than 10 hours old) and outcome in infants with meconium aspiration syndrome (MAS). We analyzed retrospectively the clinical data and initial chest roentgenograms of 65 infants who had MAS and who were admitted to NICU of Mackay Memorial Hospital in 1987. The incidence and the mortality rate in this hospital were 0.33% and 15.4% respectively. Infiltration was seen in 52, consolidation or atelectasis in 18, hyperinflation in 17, air leak in 11, and cardiomegaly in 4. The outcome was similar between infants with the first four features. Four infants with cardiomegaly also had other types of roentgenographic feature and PH value of initial blood gas less than 7.0, which means that their poor outcome was influenced by multiple factors. From this observation we concluded that the initial chest roentgenogram is a useful aid for the diagnosis and treatment of MAS, but it is not suitable for predicting the outcome of infants with MAS.