Validation study of the accuracy of echocardiographic measurements of systemic blood flow volume in newborn infants

The role of Neonatologist Performed Echocardiography in the assessment and management of neonatal shock

One of the major challenges of neonatal intensive care is the early detection and management of circulatory failure. Routine clinical assessment of the hemodynamic status of newborn infants is subjective and inaccurate, emphasizing the need for objective monitoring tools. An overview will be provided about the use of neonatologist-performed echocardiography (NPE) to assess cardiovascular compromise and guide hemodynamic management. Different techniques of central blood flow measurement, such as left and right ventricular output, superior vena cava flow, and descending aortic flow are reviewed focusing on methodology, validation, and available reference values. Recommendations are provided for individualized hemodynamic management guided by NPE.

Diminished Cardiac Performance and Left Ventricular Dimensions in Neonates with Congenital Diaphragmatic Hernia

INTRODUCTION

Newborns with congenital diaphragmatic hernia (CDH) have varying degrees of pulmonary hypoplasia and pulmonary hypertension (PH), and there is limited evidence that cardiac dysfunction is present. We sought to study early neonatal biventricular function and performance in these patients by reviewing early post-natal echocardiography (ECHO) measurements and comparing them to normal term newborns.

METHODS

Retrospective case-control study reviewing clinical and ECHO data on term newborns with CDH and normal controls born between 2009 and 2016. Patients were excluded if major anomalies, genetic syndromes, or no ECHO available. PH was assessed by ductal shunting and tricuspid regurgitant jet velocity. Speckle-tracking echocardiography was used to assess myocardial deformation using velocity vector imaging.

RESULTS

Forty-four patients with CDH and 18 age-matched controls were analyzed. Pulmonary pressures were significantly higher in the CDH cohort (systolic pulmonary arterial pressure to systolic blood pressure of 103 ± 13 vs. 78 ± 29%, p = 0.0001). CDH patients had decreased RV fractional area change (FAC - 28.6 ± 11.1 vs. 36.2 ± 9.6%, p = 0.02), tricuspid annular plane of systolic excursion (TAPSE-5.6 ± 1.6 vs. 8.6 ± 1.6 mm, p = 0.0001), and RV outflow tract stroke distance (8.6 ± 2.7 vs. 14.0 ± 4.5 cm, p = 0.0001) compared with controls. The left ventricular (LV) ejection fraction was similar in both groups, but CDH patients had a decreased LV end-diastolic volume by Simpson's rule (2.7 ± 1.0 vs. 5.0 ± 1.8 mL, p = 0.0001) and LVOT stroke distance (9.7 ± 3.4 vs. 12.6 ± 3.6 cm, p = 0.004). Biventricular global longitudinal strain (GLS) was markedly decreased in the CDH population compared to controls (RV-GLS: - 9.0 ± 5.3 vs. - 19.5 ± 1.4%, p = 0.0001; LV GLS: - 13.2 ± 5.8 vs. - 20.8 ± 3.5%, p = 0.0001).

CONCLUSION

CDH newborns have evidence of biventricular dysfunction and decreased cardiac output. Abnormal function may be a factor in the non-response to pulmonary arterial vasodilators in CDH patients. A two-pronged management strategy aimed at improving cardiac function, as well as reducing pulmonary artery pressure in CDH newborns, may be warranted.

[Impact of screening and treatment of low systemic blood flow in the prevention of severe intraventricular haemorrhage and/or death in pre-term infants]

OBJECTIVE

To assess the effect of a protocolised intervention for low systemic blood flow (SBF) in the occurrence of severe intraventricular haemorrhage (IVH) or death in pre-term infants.

METHODS

A study with a quasi-experimental design with retrospective controls was conducted on pre-term infants of less than 30weeks of gestational age, born between January 2016 and July 2017, who were consecutively included in the intervention period. The control cohort included pre-term infants (born between January 2013 and December 2015) matched by gestational age, birth weight, and gender (two controls for each case). The cases of low SBF diagnosed according to functional echocardiography during the study period received dobutamine (5-10μg/kg/min) for 48hours.

RESULTS

The study included 29 cases (intervention period) and 54 controls (pre-intervention period). Ten out of 29 (34.5%) infants received dobutamine for low SBF during the intervention period, with 3/29 (10.3%) cases of severe IVH and/or death compared to 17/54 (31.5%) in the control cohort (p=.032). There was an independent association between the intervention and a decreased occurrence of severe IVH/death after adjusting for confounding factors both in the logistic regression model [OR 0.11 (95%CI: 0.01-0.65), p=.015], as well as in the sensitivity analysis using inverse probability of treatment weighting [OR 0.23 (95%CI: 0.09-0.56); p=.001].

CONCLUSIONS

In this study with retrospective controls, a protocolised screening, and treatment for low SBF was associated with a decreased occurrence of severe IVH or death in preterm infants. Large, adequately powered trials, are needed in order to determine whether postnatal interventions directed at low SBF can improve neurological outcomes.

Investigation of EEG Activity Compared with Mean Arterial Blood Pressure in Extremely Preterm Infants

Background

Cerebral electrical activity in extremely preterm infants is affected by various factors including blood gas and circulatory parameters.

Objective

To investigate whether continuously measured invasive mean arterial blood pressure (BP) is associated with electroencephalographic (EEG) discontinuity in extremely preterm infants.

Study design

This prospective observational study examined 51 newborn infants born <29 weeks gestation in the first 3 days after birth. A single channel of raw EEG was used to quantify discontinuity. Mean BP was acquired using continuous invasive measurement and Doppler ultrasound was used to measure left ventricular output (LVO) and common carotid artery blood flow (CCAF).

Results

Median gestation and birthweight were 25.6 weeks and 760 g, respectively. Mean discontinuity reduced significantly between days 1 and 3. EEG discontinuity was significantly related to gestation, pH and BP. LVO and CCAF were not associated with EEG discontinuity.

Conclusion

Continuously measured invasive mean arterial BP was found to have a negative relationship with EEG discontinuity; increasing BP was associated with lower EEG discontinuity. This did not appear to be mediated by surrogates of systemic or cerebral blood flow. Infants receiving inotropic support had significantly increased EEG discontinuity on the first day after birth.

Advances in Diagnosis and Management of Hemodynamic Instability in Neonatal Shock

Shock in newborn infants has unique etiopathologic origins that require careful assessment to direct specific interventions. Early diagnosis is key to successful management. Unlike adults and pediatric patients, shock in newborn infants is often recognized in the uncompensated phase by the presence of hypotension, which may be too late. The routine methods of evaluation used in the adult and pediatric population are often invasive and less feasible. We aim to discuss the pathophysiology in shock in newborn infants, including the transitional changes at birth and unique features that contribute to the challenges in early identification. Special emphasis has been placed on bedside focused echocardiography/focused cardiac ultrasound, which can be used as an additional tool for early, neonatologist driven, ongoing evaluation and management. An approach to goal oriented management of shock has been described and how bed side functional echocardiography can help in making a logical choice of intervention (fluid therapy, inotropic therapy or vasopressor therapy) in infants with shock.

Echocardiographic Evaluation of Ventricular Function-For the Neonatologist and Pediatric Intensivist

In the neonatal and pediatric intensive care setting, bedside cardiac ultrasound is often used to assess ventricular dimensions and function. Depending upon the underlying disease process, it is necessary to be able to evaluate the systolic and diastolic function of left and or right ventricles. The systolic function of left ventricle is mostly assessed qualitatively on visual inspection "eye-balling" and quantitatively by measuring circumferential fraction shortening or calculating the ejection fraction by Simpson's planimetry. The assessment of left ventricular diastolic function relies essentially on the mitral valve and pulmonary venous Doppler tracings or tissue Doppler evaluation. The right ventricular particular shape and anatomical position does not permit to use the same parameters for measuring systolic function as is used for the LV. Tricuspid annular plane systolic excursion (TAPSE) and S' velocity on tissue Doppler imaging are more often used for quantitative assessment of right ventricle systolic function. Several parameters proposed to assess right ventricle systolic function such as fractional area change, 3D echocardiography, speckle tracking, and strain rate are being researched and normal values for children are being established. Diastolic function of right ventricle is evaluated by tricuspid valve and hepatic venous Doppler tracings or on tissue Doppler evaluation. The normal values for children are pretty similar to adults while normal values for the neonates, especially preterm infants, may differ significantly from adult population. The normal values for most of the parameters used to assess cardiac function in term neonates and children have now been established.

Cardiac Output Monitoring in Preterm Infants

Maintaining optimal circulatory status is a key component of preterm neonatal care. Low-cardiac output (CO) in the preterm neonate leads to inadequate perfusion of vital organs and has been linked to a variety of adverse outcomes with heightened acute morbidity and mortality and adverse neurodevelopmental outcomes. Having technology available to monitor CO allows us to detect low-output states and potentially intervene to mitigate the unwanted effects of reduced organ perfusion. There are many technologies available for the monitoring of CO in the preterm neonatal population and while many act as useful adjuncts to aid clinical decision-making no technique is perfect. In this review, we discuss the relative merits and limitations of various common methodologies available for monitoring CO in the preterm neonatal population. We will discuss the ongoing challenges in monitoring CO in the preterm neonate along with current gaps in our knowledge. We conclude by discussing emerging technologies and areas that warrant further study.

Objective cardiovascular assessment in the neonatal intensive care unit

Traditionally, cardiovascular well-being was essentially based on whether the mean blood pressure was above or below a certain value. However, this singular crude method of assessment provides limited insight into overall cardiovascular well-being. Echocardiography has become increasingly used and incorporated into clinical care. New objective modality assessments of cardiovascular status continue to evolve and are being evaluated and incorporated into clinical care. In this review article, we will discuss some of the recent advances in objective assessment of cardiovascular well-being, including the concept of multimodal monitoring. Sophisticated haemodynamic monitoring systems are being developed, including mechanisms of data acquisition and analysis. Their incorporation into clinical care represents an exciting next stage in the management of the infant with cardiovascular compromise.

Controversies in the identification and management of acute pulmonary hypertension in preterm neonates

It is increasingly recognized that the abnormal physiologic consequences of pulmonary hypertension (PH) may contribute to poor cardiopulmonary health in premature babies. Conflicting literature has led to clinical uncertainty, pathological misinterpretation, and variability in treatment approaches among practitioners. There are several disorders with overlapping and interrelated presentations, and other disorders with a similar clinical phenotype but diverse pathophysiological contributors. In this review, we provide a diagnostic approach for acute hypoxemic respiratory failure in the preterm neonate, outline the pathophysiological conditions that may present as acute PH, and discuss the implications of high pulmonary vascular resistance (PVR) on the cardiovascular system. Although PVR and respiratory management are highly interrelated, there may be a population of preterm neonates in whom inhaled nitric oxide may improve illness severity and may relate to outcomes. A management approach based on physiology that considers common clinical conundrums is provided. A more comprehensive understanding of the physiology may help in informed decision-making in clinical situations where conclusive scientific evidence is lacking. Regardless, high-quality research is required, and appropriate definition of the target population is paramount. A thoughtful approach to cardiovascular therapy may also provide an avenue to improve neurodevelopmental outcomes while awaiting more clear answers.

Golden hour of neonatal life: Need of the hour

"Golden Hour" of neonatal life is defined as the first hour of post-natal life in both preterm and term neonates. This concept in neonatology has been adopted from adult trauma where the initial first hour of trauma management is considered as golden hour. The "Golden hour" concept includes practicing all the evidence based intervention for term and preterm neonates, in the initial sixty minutes of postnatal life for better long-term outcome. Although the current evidence supports the concept of golden hour in preterm and still there is no evidence seeking the benefit of golden hour approach in term neonates, but neonatologist around the globe feel the importance of golden hour concept equally in both preterm and term neonates. Initial first hour of neonatal life includes neonatal resuscitation, post-resuscitation care, transportation of sick newborn to neonatal intensive care unit, respiratory and cardiovascular support and initial course in nursery. The studies that evaluated the concept of golden hour in preterm neonates showed marked reduction in hypothermia, hypoglycemia, intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), and retinopathy of prematurity (ROP). In this review article, we will discuss various components of neonatal care that are included in "Golden hour" of preterm and term neonatal care.

Echocardiographic Evaluation of Hemodynamics in Neonates and Children

Hemodynamic instability and inadequate cardiac performance are common in critically ill children. The clinical assessment of hemodynamic status is reliant upon physical examination supported by the clinical signs such as heart rate, blood pressure, capillary refill time, and measurement of the urine output and serum lactate. Unfortunately, all of these parameters are surrogate markers of cardiovascular well-being and they provide limited direct information regarding the adequacy of blood flow and tissue perfusion. A bedside point-of-care echocardiography can provide real-time hemodynamic information by assessing cardiac function, loading conditions (preload and afterload) and cardiac output. The echocardiography has the ability to provide longitudinal functional assessment in real time, which makes it an ideal tool for monitoring hemodynamic assessment in neonates and children. It is indispensable in the management of patients with shock, pulmonary hypertension, and patent ductus arteriosus. The echocardiography is the gold standard diagnostic tool to assess hemodynamic stability in patients with pericardial effusion, cardiac tamponade, and cardiac abnormalities such as congenital heart defects or valvar disorders. The information from echocardiography can be used to provide targeted treatment in intensive care settings such as need of fluid resuscitation versus inotropic support, choosing appropriate inotrope or vasopressor, and in providing specific interventions such as selective pulmonary vasodilators in pulmonary hypertension. The physiological information gathered from echocardiography may help in making timely, accurate, and appropriate diagnosis and providing specific treatment in sick patients. There is no surprise that use of bedside point-of-care echocardiography is rapidly gaining interest among neonatologists and intensivists, and it is now being used in clinical decision making for patients with hemodynamic instability. Like any other investigation, it has certain limitations and the most important limitation is its intermittent nature. Sometimes acquiring high quality images for precise functional assessment in a ventilated child can be challenging. Therefore, it should be used in conjunction with the existing tools (physical examination and clinical parameters) for hemodynamic assessment while making clinical decisions.

A modified echocardiographic approach improves reliability of superior vena caval flow quantification

OBJECTIVE

To assess accuracy and repeatability of a modified echocardiographic approach to quantify superior vena cava (SVC) flow volume that uses a short-axis view to directly measure SVC area and a suprasternal view to measure flow velocity, both at the level of the right pulmonary artery.

SETTING

Three tertiary-level neonatal intensive care units.

DESIGN

This was a multicentre, prospective, observational study. Accuracy of the traditional and modified approach was first assessed by comparing echo measurements according to both techniques with Phase contrast MRI (PCMRI) assessments, in a cohort of 10 neonates. In a second cohort of 40 neonates, intraobserver scan-rescan repeatability and interobserver analysis-reanalysis repeatability were assessed by repeated SVC flow echo measurements, according to both techniques.

RESULTS

The traditional echocardiographic approach to assessment of SVC flow had a moderate agreement with PCMRI (r² 0.259), a scan-rescan intraobserver repeatability index (RI) of 37% (limits of agreement (LOA) -47/+51 mL/kg/min) and an interobserver analysis-reanalysis RI of 31% (LOA -38/+40 mL/kg/min). The modified approach showed a stronger agreement with PCMRI (r² 0.775), an improved intraobserver scan-rescan repeatability (RI 22%, LOA -24/+18 mL/kg/min) and improved interobserver analysis-reanalysis repeatability (RI 18%, LOA -18/+20 mL/kg/min).

CONCLUSIONS

Echocardiographic assessment of SVC flow volume by tracing area from a short-axis view and measuring velocity-time integral from a suprasternal view offered an improvement in accuracy and repeatability, building on the traditional approach previously described.

Myocardial Injury Biomarkers in Newborns with Congenital Heart Disease

BACKGROUND

Troponin I, myoglobin, and creatine kinase-MB mass (CK-MB) are biomarkers of cardiomyocyte injury widely used in the management of adult patients. The role of these biomarkers in newborns is still not established. The purpose of this study was to evaluate the value of cardiac injury biomarkers in newborns with congenital heart disease.

METHODS

From August 2012 to January 2014, 34 newborns with a prenatal diagnosis of congenital heart disease were admitted consecutively to a neonatal intensive care unit. As controls, 20 healthy newborns were recruited. Plasma levels of cardiac biomarkers (troponin I, myoglobin, and CK-MB) were evaluated, and echocardiography was performed to evaluate cardiac function on D 1. Patients were followed during the first 28 days of life and, according to outcome, categorized as surgical or conservative treatment group.

RESULTS

Median (P25-75) levels of CK-MB were higher in patients who underwent cardiac surgery in the neonatal period [7.35 (4.90-13.40) ng/mL] than in patients who were discharged home without surgery [4.2 (2.60-5.90) ng/mL; p = 0.032]. A CK-MB cutoff of ≥ 4.6 ng/mL showed sensitivity of 87.5% and specificity of 63.6%. Troponin I and myoglobin levels were not significantly different between conservative and surgical treatment groups. CK-MB levels correlated with the tissue Doppler image of the mitral valve lateral annulus peak early/late diastolic velocity ratio (ρ = -0.480, p = 0.018).

CONCLUSION

CK-MB levels during the first hours of life were higher in newborns that needed neonatal cardiac surgery, and these levels may be an indicator of myocardial diastolic function.

Postnatal neonatal myocardial adaptation is associated with loss of tolerance to tachycardia: a simultaneous invasive and noninvasive assessment

Doppler studies at rest suggest left ventricular (LV) diastolic function rapidly improves from the neonate to infant. Whether this translates to its response to hemodynamic challenges is uncertain. We sought to explore the impact of early LV maturation on its ability to tolerate atrial tachycardia. As tachycardia reduces filling time, we hypothesized that the neonatal LV would be less tolerant of atrial tachycardia. Landrace cross piglets of two age groups (1-3 days; NPs; 14-17 days, YPs; n = 7/group) were instrumented for an atrial pacing protocol (from 200 to 300 beats/min) and assessed by invasive monitoring and echocardiography. NPs maintained their LV output and blood pressure, whereas YPs did not. Although negative dP/dt in NPs at baseline was lower than that of YPs (-1,599 ± 83 vs. -2,470 ± 226 mmHg/s, respectively, P = 0.007), with increasing tachycardia negative dP/dt converged between groups and was not different. Both groups had similar preload reduction during tachycardia; however, NPs maintained shortening fraction while YPs decreased (NPs: 35.4 ± 1.4 vs. 31.8 ± 2.2%, P = 0.35; YPs: 31.4 ± 0.8 vs. 22.9 ± 0.8%, P < 0.001). Contractility measures did not differ between groups. Peak LV twist and untwisting rate also did not differ; however, NPs tended to augment LV twist through increased apical rotation and YPs through increasing basal rotation (P = 0.009). The NPs appear more tolerant of atrial tachycardia than the YPs. They have at least similar diastolic performance, enhanced systolic performance, and different LV twist mechanics, which may contribute to improved tachycardia tolerance of NPs.

Assessment and feasibility of the four landmarks of the aortic root in a cohort of very preterm infants

Background:

The diameter of the aortic root is used as a parameter to calculate blood flow in very preterm infants. There are considerable differences in diameter of the four anatomical landmarks of the aortic root in children and adults, but limited data are available for the very preterm population. The aim of this study was to obtain reference and reliability data on two-dimensional measurements of the aortic root in very preterm infants <30 weeks gestation.

Materials and Methods:

Fifty long axis echocardiograms were reviewed and re-analyzed for measurements at the four anatomical landmarks of the aortic root; the aortic annulus, sinus of Valsalva (SV), sinotubular junction, and the proximal ascending aorta (PAA). A subjective visual scoring system was developed to quantify image quality. A random sample of images was blindly re-measured to assess intra- and inter-observer reliability.

Results:

Significant differences in diameter were found between the four landmarks, except between SV and PAA. Inter-observer coefficients showed marginal variation ranging from 5.0% to 8.2%, with slightly lower intra-observer variability. Overall image quality score was poorest for PAA on standard long axis images but improved when the probe was adjusted along the outflow tract.

Conclusion:

We present reliability and reference values for all four anatomic landmarks of the aortic root in very preterm infants and demonstrated the importance of standardizing and reporting cardiac output measurements in preterm infants.

The effect of antenatal magnesium sulfate on left ventricular afterload and myocardial function measured using deformation and rotational mechanics imaging

OBJECTIVE

Assess the effect of antenatal magnesium sulfate (MgSO4) on left ventricular function measured using deformation and rotational mechanics imaging.

STUDY DESIGN

Infants who received MgSO4 were matched for gestation, birth weight and mode of delivery with controls. Echocardiography was carried out on days 1 and 2 to measure left ventricle longitudinal strain (LV LS), twist, untwist rate, ejection fraction (EF), and systemic vascular resistance (SVR).

RESULTS

Thirty-eight infants with a median gestation and birth weight of 27.1 weeks and 923 g were included. On day 1, the MgSO4 group (n=19) had a lower SVR and higher LV LS, EF, twist and untwist rate than the Control group (n=19) (all P<0.05). There were no differences between the groups on day 2.

CONCLUSION

Antenatal MgSO4 administration is associated with a lower SVR and higher myocardial function on day 1 in preterm infants <29 weeks gestation.

Accuracy and precision of minimally-invasive cardiac output monitoring in children: a systematic review and meta-analysis

Several minimally-invasive technologies are available for cardiac output (CO) measurement in children, but the accuracy and precision of these devices have not yet been evaluated in a systematic review and meta-analysis. We conducted a comprehensive search of the medical literature in PubMed, Cochrane Library of Clinical Trials, Scopus, and Web of Science from its inception to June 2014 assessing the accuracy and precision of all minimally-invasive CO monitoring systems used in children when compared with CO monitoring reference methods. Pooled mean bias, standard deviation, and mean percentage error of included studies were calculated using a random-effects model. The inter-study heterogeneity was also assessed using an I(2) statistic. A total of 20 studies (624 patients) were included. The overall random-effects pooled bias, and mean percentage error were 0.13 ± 0.44 l min(-1) and 29.1 %, respectively. Significant inter-study heterogeneity was detected (P < 0.0001, I(2) = 98.3 %). In the sub-analysis regarding the device, electrical cardiometry showed the smallest bias (-0.03 l min(-1)) and lowest percentage error (23.6 %). Significant residual heterogeneity remained after conducting sensitivity and subgroup analyses based on the various study characteristics. By meta-regression analysis, we found no independent effects of study characteristics on weighted mean difference between reference and tested methods. Although the pooled bias was small, the mean pooled percentage error was in the gray zone of clinical applicability. In the sub-group analysis, electrical cardiometry was the device that provided the most accurate measurement. However, a high heterogeneity between studies was found, likely due to a wide range of study characteristics.

Superior vena cava flow and intraventricular haemorrhage in extremely preterm infants

OBJECTIVE

To evaluate the relationship between superior vena cava flow (SVCF) measurements within the first 24 h of life, and development of intraventricular haemorrhage (IVH) in extremely preterm infants.

STUDY DESIGN

Single centre retrospective cohort study of 108 preterm infants born less than 28 weeks' gestation. Main outcome measure was degree of IVH at day 7 postnatal age.

RESULTS

The mean GA of the study group was 25.4 weeks. Mean SVCF was lower (75 ml/kg/min) in infants later diagnosed with IVH (n = 46) compared to infants, who did not develop IVH (87.7 ml/kg/min, p = 0.055). PDA diameter was inversely associated with SVCF (p = 0.024) and reversal of flow in the descending aorta (p = 0.001). Sensitivity analysis did not confirm an independent association of SVCF with development of IVH [OR 0.990 (0.978-1.002), p = 0.115].

CONCLUSION

Our study describes early SVCF in extremely preterm infants is associated with the extent of ductal shunting, but insensitive in predicting IVH.

Neonatal echocardiography

Echocardiography is a technique within neonatal care increasingly used in acute management of patients because of its potential to guide care and hemodynamic management. However, its use continues to provoke controversy, as it was originally within the purview of pediatric cardiologists trained to identify structural as well as functional heart disease. This article examines some of the echocardiographic techniques available to the neonatologist, their applications, and the concerns surrounding their use on neonatal units.

Echocardiographic assessment of left ventricular outflow tract diameter in preterm infants

Introduction: Left ventricular output (LVO) measurement is an important part of the echocardiographic assessment of cardiac function in preterm infants. The accurate measurement of left ventricular outflow tract diameter (LVOD) is key to the calculation of LVO. Given the lack of an appropriate gold standard, we used right ventricular output (RVO) as the comparator and sought to identify the most accurate method of determining LVO in preterm infants. Methods: We studied stable preterm infants without significant cardiac shunts. LVOD was measured at the aortic valve, the aortic sinus and at the sinotubular junction. LVOs were calculated and the precision and accuracy of each was determined relative to the RVO using the Bland-Altman method. Results: 52 infants were included in this analysis. The mean difference between RVO and LVO was largest when LVOD was measured at the aortic valve and aortic sinus, +106 and -115 ml/kg/min, respectively, and smallest when measured at the sinotubular junction, 9 ml/kg/min. Limits of agreement between RVO and LVO were narrowest when LVOD was measured at the STJ. Conclusion: LVOD measurement at the sinotubular junction provides more precise and accurate measurement of LVO, in comparison to RVO, than measurement at the aortic valve or the aortic sinus.

Transitional hemodynamics in preterm infants with a respiratory management strategy directed at avoidance of mechanical ventilation

BACKGROUND

Early respiratory management of very low birth weight infants has changed over recent years to a practice of early use of CPAP with early selective surfactant administration, and decreased use of mechanical ventilation. One strategy is to use the combination of surfactant and prompt extubation to nasal continuous positive airway pressure (INtubate, SURfactant, Extubate, or INSURE). The aim of this study is to describe blood flow and ductal flow in a prospective cohort during the transitional period when this respiratory management strategy is used.

METHODS

Inborn infants <29week gestation underwent INSURE within 30min of birth using 200mg/kg Curosurf. Blood pressure and blood flow parameters (RVO, LVO, SVC flow, ductus arteriosus) were measured at 6, 24 and 72h of age and information on morbidity was collected.

RESULTS

Sixty-eight infants with a median (range) weight of 940 (450-1380) g were studied. 13 (19%) patients needed mechanical ventilation within 72h of life (INSURE failure). Blood flows and blood pressure were within reported ranges. Eleven (16%) patients had a blood pressure <gestational age and 9 (13%) patients had low blood flow.

CONCLUSION

These data show a low prevalence of low blood pressure and low blood flow in the first 3days after INSURE as compared to cohorts where mechanical ventilation was preferred during transition. We speculate that altered ventilation strategies have helped decrease the incidence of low blood flow and low blood pressure.

Non-invasive cardiac output monitoring in preterm infants undergoing patent ductus arteriosus ligation: a comparison with echocardiography

BACKGROUND

Non-invasive cardiac output monitoring (NICOM; NICOM™) may be useful in the management of extremely premature preterm infants.

OBJECTIVES

To evaluate a new bioreactance-based method of continuous NICOM in preterm infants following patent ductus arteriosus (PDA) ligation.

METHODS

Infants underwent three paired NICOM and echocardiography assessments of stroke volume (SV) and left ventricular output (LVO) in the postoperative period: at 1, 6-8, and 16-18 h postoperatively. NICOM- and echocardiography-measured SV and LVO during those periods were compared using Bland-Altman analysis and the intraclass correlation coefficient (ICC).

RESULTS

Twenty-five infants with a median (interquartile range) gestational age and birth weight of 25.0 weeks (24.5-25.9) and 700 g (615-775), respectively, were included. The overall systematic bias (limits of agreement) across all time points between the NICOM and echocardiography SV readings was 39% (8-69) with NICOM consistently underestimating echocardiography values. There was moderate consistency between NICOM and echocardiography SV values (ICC 0.78, p < 0.001). Compared with the 1-hour scans, the 6- to 8- and 16- to 18-hour scans had increased biases of 7.9% (95% CI 2.5-13.2) and 9.7% (95% CI 3.6-15.8), respectively.

CONCLUSION

Continuous LVO measurement using NICOM was feasible and demonstrated a consistent systematic bias compared with echocardiography in unstable extremely preterm infants without a PDA ligation. NICOM may be used as a trending tool for continuous monitoring in this population, but wide limits of agreement and increasing bias over time suggest it is not interchangeable with echocardiography. © 2014 S. Karger AG, Basel.