Cardiorespiratory stability during echocardiography in preterm infants

Implementing point of care ultrasound in the neonatal intensive care unit: a safety study

OBJECTIVE

Point of care ultrasound (POCUS) use is increasing in pediatrics and has been demonstrated to be superior in identifying central catheter tip location in neonatal intensive care units. However, limited data exist regarding cardiorespiratory changes secondary to POCUS in neonates.

STUDY DESIGN

A prospective observational equivalence study was performed on 50 POCUS assessments of central catheter tip location in 46 patients ≥23 weeks gestation. Heart rate (HR), respiratory rate (RR), and percent oxygen saturation (SpO2) levels were collected before and after POCUS. Limits of equivalence were set in advance.

RESULT

Equivalence was demonstrated in HR, RR, and SpO2 before and after POCUS. HR decreased by 3.24 beats per minute (90% CI: -5.36, -1.14). RR increased by 0.71 breath/min (90% CI: -1.84, +3.27). SpO2 increased by 0.54 percentage points (90% CI: -0.23, +1.31).

CONCLUSION

Identifying central catheter tip location using POCUS in neonates appears safe without affecting cardiorespiratory stability.

Neonatal Blood Pressure Standards: What Is "Normal"?

Blood pressure (BP) is routinely measured in newborn infants. Published BP nomograms demonstrate a rise in BP following delivery in healthy infants at all gestational ages (GA) and evidence that BP values are higher with increasing birth weight and GA. However, the complex physiology that occurs in newborn infants and range of BP values observed at all GA make it difficult to identify "normal" BP for a specific infant at a specific time under specific conditions. As such, complete hemodynamic assessment should include the physical examination, perinatal history, other vital signs, and laboratory values in addition to BP values.

Neonatologist performed echocardiography (NPE) in Italian neonatal intensive care units: a national survey

Background

Neonatologist performed echocardiography (NPE) has increasingly been used to assess the hemodynamic status in neonates. Aim of this survey was to investigate the utilization of NPE in Italian neonatal intensive care units (NICUs).

Methods

We conducted an on-line survey from June to September 2017. A questionnaire was developed by the Italian neonatal cardiology study group and was sent to each Italian NICU.

Results

The response rate was 77%. In 94% of Italian NICUs functional echocardiography was used by neonatologists, cardiologists or both (57, 15 and 28% respectively). All the respondents used NPE in neonates with patent ductus arteriosus and persistent pulmonary hypertension, 93% in neonates with hypotension or shock, 85% in neonates with perinatal asphyxia, 78% in suspicion of cardiac tamponade, and 73% for line positioning.

In 30% of center, there was no NPE protocol. Structural echocardiography in stable and critically ill neonates was performed exclusively by neonatologists in 46 and 36% of center respectively.

Conclusions

NPE is widely used in Italian NICUs by neonatologists. Structural echocardiography is frequently performed by neonatologists. Institutional protocols for NPE are lacking. There is an urgent need of a formal training process and accreditation to standardize the use of NPE.

Early treatment versus expectative management of patent ductus arteriosus in preterm infants: a multicentre, randomised, non-inferiority trial in Europe (BeNeDuctus trial)

BACKGROUND

Much controversy exists about the optimal management of a patent ductus arteriosus (PDA) in preterm infants, especially in those born at a gestational age (GA) less than 28 weeks. No causal relationship has been proven between a (haemodynamically significant) PDA and neonatal complications related to pulmonary hyperperfusion and/or systemic hypoperfusion. Although studies show conflicting results, a common understanding is that medical or surgical treatment of a PDA does not seem to reduce the risk of major neonatal morbidities and mortality. As the PDA might have closed spontaneously, treated children are potentially exposed to iatrogenic adverse effects. A conservative approach is gaining interest worldwide, although convincing evidence to support its use is lacking.

METHODS

This multicentre, randomised, non-inferiority trial is conducted in neonatal intensive care units. The study population consists of preterm infants (GA < 28 weeks) with an echocardiographic-confirmed PDA with a transductal diameter > 1.5 mm. Early treatment (between 24 and 72 h postnatal age) with the cyclooxygenase inhibitor (COXi) ibuprofen (IBU) is compared with an expectative management (no intervention intended to close a PDA). The primary outcome is the composite of mortality, and/or necrotising enterocolitis (NEC) Bell stage ≥ IIa, and/or bronchopulmonary dysplasia (BPD) defined as the need for supplemental oxygen, all at a postmenstrual age (PMA) of 36 weeks. Secondary outcome parameters are short term sequelae of cardiovascular failure, comorbidity and adverse events assessed during hospitalization and long-term neurodevelopmental outcome assessed at a corrected age of 2 years. Consequences regarding health economics are evaluated by cost effectiveness analysis and budget impact analysis.

DISCUSSION

As a conservative approach is gaining interest, we investigate whether in preterm infants, born at a GA less than 28 weeks, with a PDA an expectative management is non-inferior to early treatment with IBU regarding to the composite outcome of mortality and/or NEC and/or BPD at a PMA of 36 weeks.

TRIAL REGISTRATION

This trial is registered with the Dutch Trial Register NTR5479 (registered on 19 October 2015), the registry sponsored by the United States National Library of Medicine Clinicaltrials.gov NCT02884219 (registered May 2016) and the European Clinical Trials Database EudraCT 2017-001376-28 .

Introduction to neonatologist-performed echocardiography

Cardiac ultrasound techniques are increasingly used in the neonatal intensive care unit to guide cardiorespiratory care of the sick newborn. This is the first in a series of eight review articles discussing the current status of "neonatologist-performed echocardiography" (NPE). The aim of this introductory review is to discuss four key elements of NPE. Indications for scanning are summarized to give the neonatologist with echocardiography skills a clear scope of practice. The fundamental physics of ultrasound are explained to allow for image optimization and avoid erroneous conclusions from artifacts. To ensure patient safety during echocardiography recommendations are given to prevent cardiorespiratory instability, hypothermia, infection, and skin lesions. A structured approach to echocardiography, with the same standard views acquired in the same sequence at each scan, is suggested in order to ensure that the neonatologist confirms normal structural anatomy or acquires the necessary images for a pediatric cardiologist to do so when reviewing the scan.

Functional Neonatal Echocardiography: Indian Experience

INTRODUCTION

Functional echocardiography, as opposed to echocardiography as performed by the cardiologist, is the bedside utilization of cardiac ultrasound to take after functional and haemodynamic changes longitudinally. Information reflecting cardiovascular capacity and systemic and pulmonary blood flow in sick preterm and term neonates can be observed utilizing this strategy. Information is lacking on its use in neonatal units in India.

AIM

To characterize the impact of Functional neonatal echocardiography (FnECHO) programme on decision making in a tertiary care centre in India by evaluating its frequency of use, patient characteristics, and indications.

MATERIALS AND METHODS

Prospective observational study of neonates in a tertiary Neonatal Intensive Care Unit (NICU) in Pune (India) from February 2014 to January 2015. All the neonates undergoing FnECHO during this 12 month period based on clinical findings were included in the study. Data extracted from the review of the clinical notes included gestational age, birth-weight, mode of delivery, Apgar scores, details of respiratory and cardiovascular support, timing of FnECHO and any other clinical diagnosis. The findings of echocardiography were recorded and correlated with the clinical and other laboratory or X-ray findings. If these findings indicated a change in management, it was instituted.

RESULTS

A total of 348 echocardiographic studies were performed in 187 neonates (mean 1.86; SD 2.02). The most frequent indication was Patent Ductus Arteriosus (PDA) assessment (n= 174, 50%), followed by haemodynamic instability (n=43, 12.36%). The results of FnECHO modified treatment in 148 cases (42.50%) in the form of addition and/or change in the treatment or avoidance of unnecessary intervention.

CONCLUSION

FnECHO is frequently used in the NICU setting and may be a useful tool to guide treatment. PDA assessment and haemodynamic instability are the most frequent indications. To validate its usefulness, well co-ordinated large prospective studies are needed.

Utility of Targeted Neonatal Echocardiography in the Management of Neonatal Illness

OBJECTIVES

To describe the impact of targeted neonatal echocardiography on management of neonatal illness in a tertiary perinatal center neonatal intensive care unit (NICU).

METHODS

We conducted a retrospective analysis of consecutive targeted neonatal echocardiographic studies that were performed over an 18-month period in a regional perinatal center NICU in Canada. All studies were performed with a cardiovascular ultrasound machine and transducer and read on a workstation with storage and analysis software. Reporting was done on a standardized document, and any management change resulting from targeted neonatal echocardiography was documented.

RESULTS

A total of 303 consecutive targeted neonatal echocardiographic studies were performed on 129 neonates. The mean gestational age ± SD was 27.8 ± 4.3 weeks (range, 23-41 weeks), and the mean birth weight ± SD was 1196 ± 197 g (range, 490- 4500 g). The median number of studies per neonate was 2 (range, 1-8), with most repeated studies for a patent ductus arteriosus (PDA). The most common indication for echocardiography was assessment of a PDA (52.1%), followed by early global hemodynamic assessment of very low birth weight (16.2%) and pulmonary hypertension (12.2%). Of the 303 studies, 126 (41.5%) resulted in management changes. The contribution to management was significantly related to the timing of echocardiography. Around half of the echocardiographic examinations during first the week of life resulted in management changes, compared to 22% of studies after 1 week of age (P = .002). Patent ductus arteriosus management accounted for almost half of the interventions.

CONCLUSIONS

Targeted neonatal echocardiography is a valuable tool in the NICU and can contribute substantially to hemodynamic management in the first week of life, PDA management in the first 2 weeks of life, and cases of hypotension or shock at any time during the hospital stay.

Challenges in Treating Low Blood Pressure in Preterm Infants

Whilst the prevalence of low blood pressure in preterm infants seems to have fallen over the last number of years, the problem is still frequently encountered in the neonatal intensive care unit and many babies continue to receive intervention. Great variability in practice persists, with a significant number of extremely low gestational age newborns in some institutions receiving some form of intervention, and in other units substantially less. A great degree of this variability relates to the actual criteria used to define hypotension, with some using blood pressure values alone to direct therapy and others using a combination of clinical, biochemical and echocardiography findings. The choice of intervention remains unresolved with the majority of centres continuing to administer volume followed by dopamine as a first line inotrope/vasopressor agent. Despite over 40 years of use there is little evidence that dopamine is of benefit both in the short term and long-term. Long-term follow up is available in only two randomised trials, which included a total of 99 babies. An under recognized problem relates to the administration of inotrope infusions in very preterm infants. There are no pediatric specific inotrope formulations available and so risks of errors in preparation and administration remain. This manuscript outlines these challenges and proposes some potential solutions.

Does targeted neonatal echocardiography affect hemodynamics and cerebral oxygenation in extremely preterm infants?

OBJECTIVE

To investigate the effect of targeted neonatal echocardiography (TnEcho) on heart rate, arterial oxygen saturation (SPO2), cerebral regional oxygen saturation (CrSO2) and cerebral fractional oxygen extraction (CFOE) in extremely preterm infants during the first 3 postnatal days.

STUDY DESIGN

s a nested study in a prospective observational study, we acquired continuous data on heart rate, SPO2, CrSO2 and CFOE. Data averaged for the duration of TnEcho study were compared with the data collected during a baseline period immediately before the start of echocardiography. The duration of the baseline and study periods was the same. TnEcho evaluation included assessment of preload, afterload, contractility, left and right ventricular output, patent ductus arteriosus and foramen ovale.

RESULT

We analyzed 138 data pairs before and during TnEcho in 22 extremely preterm infants (gestational age 25.9 ± 1.2 weeks; range 23 to 27). There was no significant difference in heart rate between baseline and TnEcho period. There was a statistical, but clinically negligible, difference between baseline and TnEcho in SPO2 (median (quartile) 91.4% (88.9, 94.2) vs 91.3% (88.9, 94), P = 0.048), CrSO2 (76.8% (70.7, 81.5) vs 74.9% (69.5, 80.1), P<0.0001) and CFOE (15.8% (9.8, 23.6) vs 17.5% (11.3, 24.7), P<0.0001). The changes in the parameters monitored were similar in preterm infants who developed peri/intraventricular hemorrhage and in those who did not.

CONCLUSION

Although there were statistically significant changes in SPO2, CrSO2 and CFOE, the alterations were minimal and unlikely of clinical relevance. Thus, cerebral hemodynamics and systemic and cerebral oxygenation are not perturbed during TnEcho and the procedure is well tolerated by the extremely preterm infants during the postnatal transitional period.

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

BACKGROUND

The echocardiographic assessment of circulatory function in sick newborn infants has the potential to improve patient care. However, measurements are prone to error and have not been sufficiently validated. Phase-contrast magnetic resonance imaging (MRI) provides highly validated measures of blood flow and has recently been applied to the newborn population. The aim of this study was to validate measures of left ventricular output and superior vena caval flow volume in newborn infants.

METHODS

Echocardiographic and MRI assessments were performed within 1 working day of each other in a cohort of newborn infants.

RESULTS

Examinations were performed in 49 infants with a median corrected gestational age at scan of 34.43 weeks (range, 27.43-40 weeks) and a median weight at scan of 1,880 g (range, 660-3,760 g). Echocardiographic assessment of left ventricular output showed a strong correlation with MRI assessment (R(2) = 0.83; mean bias, -9.6 mL/kg/min; limits of agreement, -79.6 to +60.0 mL/kg/min; repeatability index, 28.2%). Echocardiographic assessment of superior vena caval flow showed a poor correlation with MRI assessment (R(2) = 0.22; mean bias, -13.7 mL/kg/min; limits of agreement, -89.1 to +61.7 mL/kg/min; repeatability index, 68.0%). Calculating superior vena caval flow volume from an axial area measurement and applying a 50% reduction to stroke distance to compensate for overestimation gave a slightly improved correlation with MRI (R(2) = 0.29; mean bias, 2.6 mL/kg/min; limits of agreement, -53.4 to +58.6 mL/kg/min; repeatability index, 54.5%).

CONCLUSIONS

Echocardiographic assessment of left ventricular output appears relatively robust in newborn infant. Echocardiographic assessment of superior vena caval flow is of limited accuracy in this population, casting doubt on the utility of the measurement for diagnostic decision making.

Echocardiography as a guide for patent ductus arteriosus ibuprofen treatment and efficacy prediction

OBJECTIVE

To evaluate echocardiography criteria in predicting the response to ibuprofen treatment.

DESIGN

A prospective cohort study of preterm infants untreated or treated with ibuprofen for patent ductus arteriosus.

SETTING

Three academic neonatal intensive care units.

PATIENTS

Two hundred fifty-two preterm infants of 27-31 wks gestation.

INTERVENTIONS

Ibuprofen treatment within the first 5 days of life was indicated when at least two out of four conventional echocardiography criteria were observed: ductal diameter >2 mm, left-right ductal shunt maximum velocity <2 m/sec, mean flow velocity in left pulmonary artery >0.4 m/sec, and end-diastolic flow velocity in left pulmonary artery >0.2 m/sec.

MEASUREMENTS AND MAIN RESULTS

Of the infants analyzed, 135 had a closed ductus at an average age of 1.9 ± 0.9 days, and 43 had an open ductus but <2 predefined criteria. Seventy-four infants (29%) received ibuprofen on day 2.2 ± 1.1. Sixteen infants failed ibuprofen and nine had to undergo surgical ligation. The left-right ductal shunt maximum velocity criterion had the best negative predictive value for treatment response, while the ductal diameter criterion had the best positive predictive value.

CONCLUSIONS

Echocardiography may be a useful tool to help patent ductus arteriosus management. A combined use of ductal diameter and left-right ductal shunt maximum velocity criteria allows a more accurate prediction of the response of infants with patent ductus arteriosus to ibuprofen treatment.

An exploratory investigation of some statistical summaries of oximeter oxygen saturation data from preterm babies

Aim. To explore the potential usefulness of the mean, standard deviation (SD), and coefficient of variation (CV = SD/mean) of oximeter oxygen saturations in the clinical care of preterm babies. Methods. This was an exploratory investigation involving 31 preterm babies at 36 weeks postmenstrual age. All babies were healthy, but two were considered to be clinically unstable and required greater attention. Each baby's oxygen saturations were recorded using an oximeter and summarized by the mean, SD, and CV. The potential usefulness of each measure was assessed by its ability to distinguish the two unstable babies from the others. This was achieved using box plots and hierarchical clustering together with the Calinski-Harabasz (CH) index to quantify clustering performance (higher CH index indicates stronger clustering outcome). Results. The box plots flagged both unstable babies as outliers and none of the other babies. Successful clustering of the stable and unstable babies was achieved using the CV (CH = 72.8) and SD (CH = 63.3) but not with the mean. Conclusion. Taking the box plots and clustering results together, it seems plausible that variability might be more effective than mean level for detecting instability in oxygen saturation in preterm babies and that the combination of variability and level through the CV might be even better.

The reliability of 2D and colour Doppler ultrasound in localising longline position

BACKGROUND

The position of percutaneously inserted central venous catheters (longlines) in neonates is critical, as malpositioned longlines are associated with potentially fatal complications.

AIM

To determine if cardiac ultrasound (two-dimensional (2D) and colour Doppler) is useful in evaluating longline position, when compared with the position identified by contrast radiography.

SETTING

Single level 3 neonatal unit.

PARTICIPANTS

Forty-four neonates undergoing insertion of 24-gauge silastic longlines between July 2004 and September 2005.

METHODS

Infants who had a longline inserted underwent echocardiography by a novice and an experienced operator. Operators identified longline position using a 2D then colour Doppler echocardiography during a rapid bolus infusion of saline. The position was identified from contrast radiography by two independent observers.

RESULTS

Using 2D echocardiography, the novice and experienced operators could identify 41 and 59% of longlines, respectively. However, only 34% of longlines were identified by both operators. In 15 infants whose longline positions were identified by both operators, there was agreement in only eight infants (53%). Colour Doppler improved the experienced operator's success but did not assist the novice operator. For radiographs, there was 68% agreement on longline position between observers. The experienced echocardiographer located three (7%) longlines within the heart that from radiographs were thought to be in a proximal central vessel.

CONCLUSIONS

This technique is experience-dependent and complements rather than replaces the use of contrast radiography. However, some infants with an apparently acceptable longline position on contrast radiography have longlines located within the heart on echocardiography.

Echocardiographic assessment of blood flow volume in the superior vena cava and descending aorta in the newborn infant

BACKGROUND

Clinical methods of assessing adequacy of the circulation are poor predictors of volume of blood flow in the newborn preterm. Doppler echocardiography can be used to assess perfusion at various sites in the circulation.

OBJECTIVE

To assess repeatability of measurement of volume of superior vena caval (SVC) and descending aortic (DAo) flow.

DESIGN

SVC and DAo flow volume were assessed four times in the first 48 h of postnatal life in a cohort of preterm (<31 weeks) infants. Within-observer and between-observer repeatability was assessed in a subgroup of preterm infants. Normative values were derived from 14 preterm infants who required <48 h respiratory support and 13 healthy term infants.

RESULTS

Within-observer repeatability coefficient was 30 ml/kg/min for quantification of SVC flow, and 2.2 cm for DAo stroke distance. Measurement of DAo diameter had poor repeatability. Between-observer repeatability appeared poorer than within-observer repeatability. The fifth centile for volume of SVC flow in healthy preterm infants was 55 ml/kg/min and 4.5 cm for DAo stroke distance.

CONCLUSIONS

Echocardiographic assessments of volume of SVC flow and velocity of DAo flow have similar within-observer repeatability to other neonatal haemodynamic measurements. Between-observer repeatability for both measurements was poor, reflecting the difficulty of standardising these novel techniques. In this small cohort of preterm infants, SVC flow volume <55 ml/kg/min and DAo stroke distance <4.5 cm represented low or borderline systemic perfusion in the first 48 h of postnatal life.