Accuracy and repeatability of pediatric cardiac output measurement using Doppler: 20-year review of the literature

Accuracy of Respiratory Variation in Inferior Vena Cava Diameter to Predict Fluid Responsiveness in Children Under Mechanical Ventilation

Proper assessment of fluid responsiveness using accurate predictors is crucial to guide fluid therapy and avoid the serious adverse effects of fluid overload. The main objective of this study was to investigate the accuracy of respiratory variations in inferior vena cava diameter (∆IVC) to predict fluid responsiveness in mechanically ventilated children. This prospective single-center study included 32 children (median age and weight of 17 months and 10 kg, respectively) who received a fluid infusion of 10 ml kg-1 of crystalloid solutions over 10 min. ∆IVC and respiratory variation in aortic blood flow peak velocity (∆Vpeak) were determined over one controlled respiratory cycle before and after fluid loading. Thirteen (41%) participants were fluid-responders. ∆IVC, ∆Vpeak, stroke volume index, and cardiac index were found to be predictors of fluid responsiveness. However, the area under the ROC curve of ∆IVC was smaller when compared to ∆Vpeak (0.709 vs. 0.935, p < 0.012). The best cut-off values were 7.7% for ∆IVC (sensitivity, 69.2%; specificity 78.9%, positive predictive value, 69.2%; and negative predictive value, 78.9%) and 18.2% for ∆Vpeak (sensitivity, 84.6%; specificity, 89.5%; positive predictive value, 84.6%; negative predictive value, 89.5%). Changes in stroke volume were positively correlated with ∆IVC (ρ = 0.566, p < 0.001) and ∆Vpeak (ρ = 0.603, p < 0.001). A significant correlation was also found between changes in MAP and ∆Vpeak (ρ = 0.382; p = 0.031), but the same was not observed with ∆IVC (ρ = 0.011; p = 0.951). In conclusion, ∆IVC was found to have a moderate accuracy in predicting fluid responsiveness in mechanically ventilated children and is an inferior predictor when compared to ∆Vpeak.

Association between patent ductus arteriosus flow and home oxygen therapy in extremely preterm infants

BACKGROUND

Central blood flow measurements include the estimation of right and left ventricular output (RVO, LVO), superior vena cava (SVC) flow, and calculated patent ductus arteriosus (PDA) flow. We aimed to provide an overview of the maturation patterns of these values and the relationship between PDA flow and the need for home oxygen therapy.

METHODS

This prospective single-center study was conducted in infants born at <26 weeks of gestation. We performed echocardiographic measurements five times during their life (from the 4th post-natal day to the 36th postmenstrual week).

RESULTS

Sixty patients with a mean birth weight of 680 (590, 760) g were included. Postnatal development of LVO and PDA flow peaked at the end of the second postnatal week (427 and 66 mL/kg/min, respectively). The RVO increased between days 4 and 7-8. The SVCF was most stable. The development curves of PDA flow differed between the groups with (n = 28; 47%) and without home oxygen therapy.

CONCLUSION

We present the central blood flow values and their postnatal development in infants <26 weeks of gestation. This study demonstrates the association between PDA flow and the future need for home oxygen therapy.

IMPACT

This study enriches our knowledge of the long-term development of central blood flow parameters and derived patent ductus arteriosus (PDA) flow in extremely preterm infants (<26 weeks). While pulmonary resistance decreased, PDA flow continued to increase from day 4 to the end of the second week of life. Similarly, left ventricular output increased as a marker of preload. The superior vena cava flow remained stable. The observed association between PDA flow and an unfavorable respiratory outcome is important for future studies focusing on the prevention of chronic lung disease.

Guidelines and Recommendations for Targeted Neonatal Echocardiography and Cardiac Point-of-Care Ultrasound in the Neonatal Intensive Care Unit: An Update from the American Society of Echocardiography

Targeted neonatal echocardiography (TNE) involves the use of comprehensive echocardiography to appraise cardiovascular physiology and neonatal hemodynamics to enhance diagnostic and therapeutic precision in the neonatal intensive care unit. Since the last publication of guidelines for TNE in 2011, the field has matured through the development of formalized neonatal hemodynamics fellowships, clinical programs, and the expansion of scientific knowledge to further enhance clinical care. The most common indications for TNE include adjudication of hemodynamic significance of a patent ductus arteriosus, evaluation of acute and chronic pulmonary hypertension, evaluation of right and left ventricular systolic and/or diastolic function, and screening for pericardial effusions and/or malpositioned central catheters. Neonatal cardiac point-of-care ultrasound (cPOCUS) is a limited cardiovascular evaluation which may include line tip evaluation, identification of pericardial effusion and differentiation of hypovolemia from severe impairment in myocardial contractility in the hemodynamically unstable neonate. This document is the product of an American Society of Echocardiography task force composed of representatives from neonatology-hemodynamics, pediatric cardiology, pediatric cardiac sonography, and neonatology-cPOCUS. This document provides (1) guidance on the purpose and rationale for both TNE and cPOCUS, (2) an overview of the components of a standard TNE and cPOCUS evaluation, (3) disease and/or clinical scenario-based indications for TNE, (4) training and competency-based evaluative requirements for both TNE and cPOCUS, and (5) components of quality assurance. The writing group would like to acknowledge the contributions of Dr. Regan Giesinger who sadly passed during the final revisions phase of these guidelines. Her contributions to the field of neonatal hemodynamics were immense.

Cardiac output monitoring in children: a review

Cardiac output monitoring enables physiology-directed management of critically ill children and aids in the early detection of clinical deterioration. Multiple invasive techniques have been developed and have demonstrated ability to improve clinical outcomes. However, all require invasive arterial or venous catheters, with associated risks of infection, thrombosis and vascular injury. Non-invasive monitoring of cardiac output and fluid responsiveness in infants and children is an active area of interest and several proven techniques are available. Novel non-invasive cardiac output monitors offer a promising alternative to echocardiography and have proven their ability to influence clinical practice. Assessment of perfusion remains a challenge; however, technologies such as near-infrared spectroscopy and photoplethysmography may prove valuable clinical adjuncts in the future.

Automatic Prediction of Paediatric Cardiac Output From Echocardiograms Using Deep Learning Models

Background

Cardiac output (CO) perturbations are common and cause significant morbidity and mortality. Accurate CO assessment is crucial for guiding treatment in anaesthesia and critical care, but measurement is difficult, even for experts. Artificial intelligence methods show promise as alternatives for accurate, rapid CO assessment.

Methods

We reviewed paediatric echocardiograms with normal CO and a dilated cardiomyopathy patient group with reduced CO. Experts measured the left ventricular outflow tract diameter, velocity time integral, CO, and cardiac index (CI). EchoNet-Dynamic is a deep learning model for estimation of ejection fraction in adults. We modified this model to predict the left ventricular outflow tract diameter and retrained it on paediatric data. We developed a novel deep learning approach for velocity time integral estimation. The combined models enable automatic prediction of CO. We evaluated the models against expert measurements. Primary outcomes were root-mean-squared error, mean absolute error, mean average percentage error, and coefficient of determination (R2).

Results

In a test set unused during training, CI was estimated with the root-mean-squared error of 0.389 L/min/m2, mean absolute error of 0.321 L/min/m2, mean average percentage error of 10.8%, and R2 of 0.755. The Bland-Altman analysis showed that the models estimated CI with a bias of +0.14 L/min/m2 and 95% limits of agreement -0.58 to 0.86 L/min/m2.

Conclusions

Our model estimated CO with strong correlation to ground truth and a bias of 0.17 L/min, better than many CO measurements in paediatrics. Model pretraining enabled accurate estimation despite a small dataset. Potential uses include supporting clinicians in real-time bedside calculation of CO, identification of low-CO states, and treatment responses.

Point-of-care ultrasonography to predict fluid responsiveness in children: A systematic review and meta-analysis

BACKGROUND

Point-of-care ultrasonography (POCUS) is proposed as a valuable method for hemodynamic monitoring and several ultrasound-based predictors of fluid responsiveness have been studied. The main objective of this study was to assess the accuracy of these predictors in children.

METHODS

PubMed, Embase, Scopus, ClinicalTrials.gov, and Cochrane Library databases were searched for relevant publications through July 2022. Pediatric studies reporting accuracy estimates of ultrasonographic predictors of fluid responsiveness were included since they had used a standard definition of fluid responsiveness and had performed an adequate fluid challenge.

RESULTS

Twenty-three studies involving 1028 fluid boluses were included, and 12 predictors were identified. A positive response to fluid infusion was observed in 59.7% of cases. The vast majority of participants were mechanically ventilated (93.4%). The respiratory variation in aortic blood flow peak velocity (∆Vpeak) was the most studied predictor, followed by the respiratory variation in inferior vena cava diameter (∆IVC). The pooled sensitivity and specificity of ∆Vpeak were 0.84 (95% CI, 0.76-0.90) and 0.82 (95% CI, 0.75-0.87), respectively, and the area under the summary receiver operating characteristic curve (AUSROC) was 0.89 (95% CI, 0.86-0.92). The ∆IVC presented a pooled sensitivity and specificity of 0.79 (95% CI, 0.62-0.90) and 0.70 (95% CI, 0.51-0.84), respectively, and an AUSROC of 0.81 (95% CI, 0.78-0.85). Significant heterogeneity in accuracy estimates across studies was observed.

CONCLUSIONS

POCUS has the potential to accurately predict fluid responsiveness in children. However, only ∆Vpeak was found to be a reliable predictor. There is a lack of evidence supporting the use of POCUS to guide fluid therapy in spontaneously breathing children.

Pulse Wave Analysis Using the Pressure Recording Analytical Method to Measure Cardiac Output in Pediatric Cardiac Surgery Patients: A Method Comparison Study Using Transesophageal Doppler Echocardiography as Reference Method

BACKGROUND

Cardiac output (CO) is a key determinant of oxygen delivery, but choosing the optimal method to obtain CO in pediatric patients remains challenging. The pressure recording analytical method (PRAM), implemented in the MostCareUp system (Vygon), is an invasive uncalibrated pulse wave analysis (PWA) method to measure CO. The objective of this study is to compare CO measured by PRAM (PRAM-CO; test method) with CO simultaneously measured by transesophageal Doppler echocardiography (TEE-CO; reference method) in pediatric patients.

METHODS

In this prospective observational method comparison study, PRAM-CO and TEE-CO were assessed in pediatric elective cardiac surgery patients at 2 time points: after anesthesia induction and after surgery. The study was performed in a German university medical center from March 2019 to March 2020. We included pediatric patients scheduled for elective cardiac surgery with arterial catheter and TEE monitoring. PRAM-CO and TEE-CO were compared using Bland-Altman analysis accounting for repeated measurements per subject, and the percentage error (PE).

RESULTS

We included 52 PRAM-CO and TEE-CO measurement pairs of 30 patients in the final analysis. Mean ± SD TEE-CO was 2.15 ± 1.31 L/min (range 0.55-6.07 L/min), and mean PRAM-CO was 2.21 ± 1.38 L/min (range 0.55-5.90 L/min). The mean of the differences between TEE-CO and PRAM-CO was -0.06 ±0.38 L/min with 95% limits of agreement (LOA) of 0.69 (95% confidence interval [CI], 0.53-0.82 L/min) to -0.80 L/min (95% CI, -1.00 to -0.57 L/min). The resulting PE was 34% (95% CI, 27%-41%).

CONCLUSIONS

With a PE of <45%, PRAM-CO shows clinically acceptable agreement with TEE-CO in hemodynamically stable pediatric patients before and after cardiac surgery.

Carotid Doppler Ultrasonography for Hemodynamic Assessment in Critically Ill Children

An accurate assessment of cardiovascular performance is essential to predict and evaluate hemodynamic response to interventions. The objective of this prospective study was to assess whether point-of-care ultrasonography of the common carotid artery (CCA) can estimate the stroke volume (SV) and cardiac index (Ci) of critically ill children. Participants underwent Doppler ultrasonography of the left CCA and transthoracic echocardiography (TTE). Variables measured by TTE were SV and Ci. Carotid blood flow (CBF) was calculated based on both systolic velocity-time integral (CBF_(s)) and total velocity-time integral (CBF_(t)). Carotid corrected flow time(CFT)was also determined. A total of 50 children were enrolled. The median age and weight of participants were 36.0 months and 14.2 kg, respectively. Both CBF_(s) and CBF_(t) correlated very strongly with SV (ρ = 0.98 and 0.97, respectively) and Ci (ρ = 0.96 and 0.92, respectively). Agreement analysis showed low biases and clinically acceptable percentage errors between variables measured by TTE (SV and Ci) and those estimated by Doppler ultrasonography. Linear regression analysis revealed that the Ci of mechanically ventilated children can be estimated by the following equation: [Formula: see text]. CFT did not significantly correlate with SV or Ci (ρ = 0.27 and 0.05, respectively). Doppler ultrasonography of the left CCA is able to estimate the SV and Ci of critically ill children. Therefore, the CDU may be considered as an alternative for estimating Ci in critically ill children when TTE is not feasible or available.

Comparison of Cardiac Output Measurement by Electrical Velocimetry with Echocardiography in Extremely Low Birth Weight Neonates

INTRODUCTION

Electrical velocimetry (EV) offers a noninvasive tool for continuous cardiac output (CO) measurements which might facilitate hemodynamic monitoring and targeted therapy in low birth neonates, in whom other methods of CO measurement are not practicably feasible.

METHODS

This prospective observational study compared simultaneous cardiac output measurements by electrical velocimetry (COEV) with transthoracic echocardiography (COTTE) in extremely low birth weight (ELBW) neonates in the neonatal intensive care unit (NICU). Echocardiography was performed by 1 single examiner. Data were analyzed by Bland-Altman analysis and independent-samples analysis of variance. A mean percentage error (MPE) of <30% and limits of agreement (LOA) up to ±30% were considered clinically acceptable.

RESULTS

Thirty-eight ELBW neonates were studied and yielded 85 pairs of COEV and COTTE measurements. Bland-Altman analysis showed an overall bias (the mean difference) and LOA of -126 and -305 to +52 mL min-1, respectively, and an MPE of 66%. Patients with patent ductus arteriosus had a higher bias with LOA and MPE of -166.8, -370.7 to +37 mL min-1, and 69%, respectively. The overall true precision was 58%.

CONCLUSION

This study showed high bias and lack of agreement between EV and TTE for measurement of CO in ELBW infants in NICU, limiting applicability of EV to monitor absolute values.

Neonatologist Performed Echocardiography for Evaluating the Newborn Infant

The interest in the use of cardiac ultrasound for hemodynamic evaluation in neonates has increased in the last decades. Several overlapping terms exists, and a non-comprehensive list includes point-of-care ultrasound, clinician-performed ultrasound, focused cardiac ultrasound, targeted neonatal echocardiography, and neonatologist performed echocardiography. This review will use the term neonatologist performed echocardiography. Neonatologist performed echocardiography is primarily echocardiography to obtain snapshots of hemodynamics and heart function, usually as repeated exams during intensive care. It provides the neonatologist with in-depth information on the hemodynamics not available by blood pressure, pulse oximetry, capillary refill time, and various blood tests. The review provides a brief overview of some relevant methods for assessment of hemodynamics and heart function. It does not discuss training, implementation, accreditation, and certification nor in-depth technical aspects and detailed use of neonatologist performed echocardiography. If the information obtainable by neonatologist performed echocardiography had been accessible easily (e.g., via a sensor put on the neonate similarly to a pulse oximeter), neonatologist performed echocardiography would have been more widely used. Acquiring skills for neonatologist performed echocardiography take time and resources. Future developments probably include a stronger focus on education, training, and certification. It is likely that echocardiographic methods will evolve further, probably involving establishing new indexes and methods and implementing artificial intelligence in the analyses procedure to improve accuracy and workflow. It is important to acknowledge that neonatologist performed echocardiography is not a therapeutic intervention; it is a diagnostic tool providing additional information.

Perioperative anesthesia care for the pediatric patient undergoing a kidney transplantation: An educational review

Living-donor kidney transplantation is the first choice therapy for children with end-stage renal disease and shows good long-term outcome. Etiology of renal failure, co-morbidities, and hemodynamic effects, due to donor-recipient size mismatch, differs significantly from those in adult patients. Despite the complexities related to both patient and surgery, there is a lack of evidence-based anesthesia guidelines for pediatric kidney transplantation. This educational review summarizes the pathophysiological changes to consider and suggests recommendations for perioperative anesthesia care, based on recent research papers.

Consistency between Impedance Technique and Echocardiogram Hemodynamic Measurements in Neonates

OBJECTIVE

The aim of this study was to validate impedance technique (IT) by investigating the agreement in cardiac output measurements performed by IT and echocardiography (ECHO).

STUDY DESIGN

This is a prospective observational study, including a total of 30 neonates who underwent hemodynamic measurements by IT and ECHO. To determine the agreement between both methods, we performed IT to measure stroke volume (SV-IT) and cardiac output (CO-IT) immediately before or after ECHO to measure SV (SV-ECHO) and CO (CO-ECHO). The precision and accuracy of the IT relative to ECHO were assessed.

RESULTS

SV-ECHO and SV-IT were (4.45 ± 0.78) and (4.54 ± 0.81) mL, respectively. The bias and limits of agreement of SV-IT were 0.09 mL and ( -1.92 to 1.73) mL, respectively. The true precision of SV-IT was 27.3%. Furthermore, CO-ECHO and CO-IT were (0.62 ± 0.12) and (0.61 ± 0.12) L/min, respectively. The bias and LoA of CO-IT were 0.01L/min and (-0.33 to 0.31) L/min, respectively. The true precision of CO-IT was 28.3%.

CONCLUSION

Agreement between the IT and ECHO in the cardiac output measurement appeared acceptable. However, the accuracy and precision of the IT approach should be further investigated using a larger sample.

Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler

BACKGROUND

The objective of this study was to compare esophageal Doppler cardiac output (COEDM) against the reference method effective pulmonary blood flow cardiac output (COEPBF), for agreement of absolute values and ability to detect change in cardiac output (CO) in pediatric surgical patients. Furthermore, the relationship between these 2 methods and noninvasive blood pressure (NIBP) parameters was evaluated.

METHODS

Fifteen children American Society of Anesthesiology (ASA) I and II (median age, 8 months; median weight, 9 kg) scheduled for surgery were investigated in this prospective observational cohort study. Baseline COEPBF/COEDM/NIBP measurements were made at positive end-expiratory pressure (PEEP) 3 cm H2O. PEEP was increased to 10 cm H2O and COEPBF/COEDM/NIBP was recorded after 1 and 3 minutes. PEEP was then lowered to 3 cm H2O, and all measurements were repeated after 3 minutes. Finally, 20-µg kg-1 intravenous atropine was given with the intent to increase CO, and all measurements were recorded again after 5 minutes. Paired recordings of COEDM and COEPBF were examined for agreement and trending ability, and all parameters were analyzed for their responses to the hemodynamic challenges.

RESULTS

Bias between COEDM and COEPBF (COEDM - COEPBF) was -17 mL kg-1 min-1 (limits of agreement, -67 to +33 mL kg-1 min-1) with a mean percentage error of 32% (95% confidence interval [CI], 25-37) and a concordance rate of 71% (95% CI, 63-80). The hemodynamic interventions caused by PEEP manipulations resulted in significant decrease in COEPBF absolute numbers (155 mL kg-1 min-1 [95% CI, 151-159] to 127 mL kg-1 min-1 [95% CI, 113-141]) and a corresponding relative decrease of 18% (95% CI, 14-22) 3 minutes after application of PEEP 10. No corresponding decreases were detected by COEDM. Mean arterial pressure showed a relative decrease with 5 (95% CI, 2-8) and 6% (95% CI, 2-10) 1 and 3 minutes after the application of PEEP 10, respectively. Systolic arterial pressure showed a relative decrease of 5% (95% CI, 2-10) 3 minutes after application of PEEP 10. None of the recorded parameters responded to atropine administration except for heart rate that showed a 4% relative increase (95% CI, 1-7, P = .02) 5 minutes after atropine.

CONCLUSIONS

COEDM was unable to detect the reduction of CO cause by increased PEEP, whereas COEPBF and to a minimal extent NIBP detected these changes in CO. The ability of COEPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that COEPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children.

Development of in-airway laser absorption spectroscopy for respiratory based measurements of cardiac output

Respiratory approaches to determining cardiac output in humans are securely rooted in mass balance and therefore potentially highly accurate. To address existing limitations in the gas analysis, we developed an in-airway analyser based on laser absorption spectroscopy to provide analyses every 10 ms. The technique for estimating cardiac output requires both a relatively soluble and insoluble tracer gas, and we employed acetylene and methane for these, respectively. A multipass cell was used to provide sufficient measurement sensitivity to enable analysis directly within the main gas stream, thus avoiding errors introduced by sidestream gas analysis. To assess performance, measurements of cardiac output were made during both rest and exercise on five successive days in each of six volunteers. The measurements were extremely repeatable (coefficient of variation ~ 7%). This new measurement technology provides a stable foundation against which the algorithm to calculate cardiac output can be further developed.

Harnessing Machine Intelligence in Automatic Echocardiogram Analysis: Current Status, Limitations, and Future Directions

Echocardiography (echo) is a critical tool in diagnosing various cardiovascular diseases. Despite its diagnostic and prognostic value, interpretation and analysis of echo images are still widely performed manually by echocardiographers. A plethora of algorithms has been proposed to analyze medical ultrasound data using signal processing and machine learning techniques. These algorithms provided opportunities for developing automated echo analysis and interpretation systems. The automated approach can significantly assist in decreasing the variability and burden associated with manual image measurements. In this paper, we review the state-of-the-art automatic methods for analyzing echocardiography data. Particularly, we comprehensively and systematically review existing methods of four major tasks: echo quality assessment, view classification, boundary segmentation, and disease diagnosis. Our review covers three echo imaging modes, which are B-mode, M-mode, and Doppler. We also discuss the challenges and limitations of current methods and outline the most pressing directions for future research. In summary, this review presents the current status of automatic echo analysis and discusses the challenges that need to be addressed to obtain robust systems suitable for efficient use in clinical settings or point-of-care testing.

Echocardiographic Parameters Predictive of Poor Outcome in Persistent Pulmonary Hypertension of the Newborn (PPHN): Preliminary Results

The aim is to conduct a pilot study to prospectively describe echocardiographic parameters in neonates with pulmonary hypertension (PH) managed according to current recommendations and to identify those parameters that could predict worsening of short-term outcomes. All neonates less than 28 days old with a diagnosis of PH were prospectively enrolled in a tertiary care center for 1 year. Two echocardiograms were performed by a trained neonatologist. The first echocardiogram was performed at the time of diagnosis, whereas the second was performed just after basic therapeutic optimization. The cohort included 27 neonates. Mean gestational age at birth was 36.1 weeks gestational age (WGA) (SD: 4) and mean birth weight was 2658 g (SD: 907). Six neonates (22%) died before day 28, with a median age at death of 48 h (IQR [33; 89]). Although the first echocardiogram showed no difference, the second highlighted a strong link between the persistence of right-to left-shunt and death (p = 0.002). We showed a link between right-to-left shunt and a poor outcome (death or morbidity) after therapeutic optimization among premature and full-term neonates suffering from PH. We recommend repeating echocardiography after basic therapeutic optimization and for prognostic purposes, taking into account only the second examination. Larger cohorts are needed to confirm these results.

Functional echocardiography training in the neonatal intensive care unit: comparing measurements and results with the pediatric cardiologist

OBJECTIVES

Functional echocardiography is a valuable tool in the neonatal intensive care unit, but training programs are not standardized. The aim was to report an functional echocardiography training program for neonatologists and to describe the agreement of their measurements with the pediatric cardiologist.

METHODS

Functional echocardiography training lasted 32h. After training program, the neonatologists performed functional echocardiography in the neonatal intensive care unit and were required to measure left cardiac chambers dimensions, left ventricle systolic function, right and left ventricular output, ductus arteriosus diameter, and flow pattern. Images were recorded by the equipment and reviewed offline by the pediatric cardiologist. The Bland-Altman test was used for quantitative variables and the kappa test, for qualitative variables.

RESULTS

Twenty-two trained neonatologists performed 100 functional echocardiography exams. Ductus arteriosus identification and flow pattern had substantial agreement (kappa=0.91 and 0.88, respectively), as well as its diameter (mean difference=0.04mm). The mean difference for the aortic root was -1.2mm; left atrium, 0.60mm; left ventricle diastolic diameter, -0.90mm; left ventricle systolic diameter, -0.30mm. Shortening fraction and ejection fraction correlated well with broad limits of agreement, -2.96% (14.88; -20.82%) and --3.43% (15.54; -22.40%), respectively. Right and left ventricular output had broad limits of agreement, 16.69mL/kg/min (222.76; -189.37) and 23.57mL/kg/min (157.88; -110), respectively. There was good agreement between interpretations of normal or low cardiac output (76.7% for right ventricular output; 75.7% for left ventricular output).

CONCLUSION

This functional echocardiography training program enabled neonatologists to obtain adequate skills in performing the images, obtaining good agreement with the cardiologist in simple hemodynamic measurements and ductus arteriosus evaluation.

Advanced Hemodynamic Monitoring in the Neonatal Intensive Care Unit

Clinical assessment of cardiac output by interpretation of indirect parameters has proven to be inaccurate, irrespective of the level of experience of the clinician. Objective cardiac output monitoring is feasible in newborn infants in intensive care. The most promising methods include transthoracic echocardiography, transcutaneous Doppler, electrical biosensing technologies, transpulmonary ultrasound dilution, and arterial pulse contour analysis. Simultaneous assessment of blood pressure and cardiac output enables the identification of the earliest stage of shock. Comprehensive hemodynamic monitoring is pivotal for an individualized pathophysiology-based hemodynamic management.

The Future of Cardiac Ultrasound in the Neonatal Intensive Care Unit

Cardiac ultrasound is increasingly used to guide hemodynamic decision making in the neonatal intensive care unit (NICU). This article focuses on likely future progress in training, accreditation, digital connectivity, miniaturization, and modality development. Many documents have been published internationally to guide cardiac ultrasound training, accreditation, and implementation in the NICU, but challenges remain in providing assessments of hemodynamic status without risking missed structural diagnoses. Advances in simulation training and digital connectivity provide an opportunity to standardize approaches across institutions and continents. Development of machine learning and ultrasound modalities in turn provide huge scope for improving robustness and completeness of assessment.

Respiratory Variations in Aortic Blood Flow to Predict Volume Responsiveness in Ventilated Children With Leukemia and Neutropenic Septic Shock

OBJECTIVES

To investigate whether respiratory variations in aortic blood flow by echocardiography can accurately predict volume responsiveness in ventilated children with leukemia and neutropenic septic shock.

DESIGN

A prospective study.

SETTING

A 25-bed PICU of a tertiary hospital.

PATIENTS

Mechanically ventilated children with leukemia who had been exposed to anthracyclines and exhibited neutropenic septic shock were enrolled.

INTERVENTIONS

Transthoracic echocardiography was performed to monitor the aortic blood flow before and after fluid administration.

MEASUREMENTS AND MAIN RESULTS

After volume expansion, left ventricular stroke volume increased by greater than or equal to 15% in 16 patients (responders) and less than 15% in 14 patients (nonresponders). The performance of respiratory variation in velocity time integral of aortic blood flow and respiratory variation in peak velocity of aortic blood flow for predicting volume responsiveness, as determined by the area under the receiver operating characteristic curve, was 0.74 (95% CI, 0.55-0.94; p = 0.025) and 0.71 (95% CI, 0.53-0.90; p = 0.048), respectively. Positive end-expiratory pressure was higher in nonresponders than in responders (p = 0.035).

CONCLUSIONS

Respiratory variation in velocity time integral of aortic blood flow and respiratory variation in peak velocity of aortic blood flow derived from transthoracic echocardiography showed only a fair reliability in predicting volume responsiveness in ventilated children with leukemia and neutropenic septic shock.

Does a two-minute mini-fluid challenge predict fluid responsiveness in pediatric patients under general anesthesia?

BACKGROUND

Very little evidence for predictive markers of fluid responsiveness has been reported in children as compared to adults. The impact of hypovolemia or hypervolemia on morbidity has driven interest in the fluid challenge titration strategy.

AIM

The objective of this study was to explore the ability of a 3 mL kg^-1 mini-fluid challenge over 2 minutes to predict fluid responsiveness in children under controlled ventilation.

METHODS

Children scheduled for surgery under general anesthesia were included and received a fluid challenge of 15 mL kg^-1 of crystalloid prior to incision administered over 10 minutes in two steps: 3 mL kg^-1 over 2 minutes then 12 mL kg^-1 over 8 minutes. Fluid responsiveness was defined as a change of ≥10% in cardiac output estimated by left ventricular outflow tract velocity time integral (VTI) as measured by transthoracic ultrasound before and after the fluid challenge of 15 mL kg^-1 .

RESULTS

Of the 55 patients included in the analysis, 43 were fluid responders. The increase in the VTI after the mini-fluid challenge (ΔVTI_miniFC ) predicted fluid responsiveness with an area under the receiver operating characteristic curve of 0.77; 95% CI (0.63-0.87), P = .004. Considering the least significant change which was 7.9%; 95% CI (6-10), the threshold was 8% with a sensitivity of 53%; 95% CI (38-68); and a specificity of 77%; 95% CI (54-100).

CONCLUSION

ΔVTI_miniFC weakly predicted the effects of a fluid challenge of 15 mL kg^-1 of crystalloid in anesthetized children under controlled mechanical ventilation.

Physiological Responses to Exercise in Pediatric Heart Transplant Recipients

INTRODUCTION

Pediatric heart transplant (HTx) recipients have reduced exercise capacity typically two-thirds of predicted values, the mechanisms of which are not fully understood. We sought to assess the cardiorespiratory responses to progressive exercise in HTx relative to controls matched for age, sex, body size, and work rate.

METHODS

Fourteen HTx recipients and matched controls underwent exercise stress echocardiography on a semisupine cycle ergometer. Hemodynamics, left ventricular (LV) dimensions, and volumes were obtained and indexed to body surface area. Oxygen consumption (V˙O2) was measured, and arteriovenous oxygen difference was estimated using the Fick Principle.

RESULTS

At rest, LV mass index (P = 0.03) and volumes (P < 0.001) were significantly smaller in HTx, whereas wall thickness (P < 0.01) and LV mass-to-volume ratio (P = 0.01) were greater. Differences in LV dimensions and stroke volume persisted throughout exercise, but the pattern of response was similar between groups as HR increased. As exercise progressed, heart rate and cardiac index increased to a lesser extent in HTx. Despite this, V˙O2 was similar (P = 0.82) at equivalent work rates as HTx had a greater change in arteriovenous oxygen difference (P < 0.01).

CONCLUSIONS

When matched for work rate, HTx had similar metabolic responses to controls despite having smaller LV chambers and an attenuated increase in hemodynamic responses. These findings suggest that HTx may increase peripheral O2 extraction as a compensatory mechanism in response to reduced cardiovascular function.

Assessment of cardiac function in infants with transposition of the great arteries after surgery: comparison of two methods

BACKGROUND

Assessment of cardiac function is crucial in pediatric patients undergoing cardiovascular surgery, monitoring cardiac output and changing hemodynamic conditions during surgery accordingly is important to improve post-surgical outcome. We aimed to measure cardiac index (CI) and maximal rate of the increase of left ventricular pressure dp/dt(max) with the pressure recording analytic method (PRAM, MostCare^®) and compared it with transthoracic echocardiographic cardiac index estimation in infants with transposition of the great arteries (TGA) undergoing surgical correction.

METHODS

We enrolled 74 infants with TGA consecutively into this study. CI and dp/dt(max) were measured with PRAM and echocardiography at 0, 4, 8, 12, 24 and 48 h postoperatively. Blood brain natriuretic peptide (BNP) and blood lactate (Lac) were measured at baseline and after operation.

RESULTS

The median age at surgery was 13 days (range 1-25 days) with an average weight of 3.24 kg (range 2.31-4.17 kg). CI estimated by PRAM was 1.11 ± 0.12 L/min/m² (range 0.69-1.36) and by Doppler echocardiography was 1.13 ± 0.13 L/min/m² (range 0.76-1.40). dp/dt(max) estimated by PRAM was 1.31 ± 0.03 mmHg/s (range 1.23-1.43) and by Doppler echocardiography was 1.31 ± 0.04 L/min/m² (range 1.25-1.47). CI (r = 0.817, P < 0.001) and dp/dt(max) (r = 0.794, P < 0.001) measured by two methods were highly correlated with a linear relation. Blood BNP and lactate increased to the highest level at 8-12 h post-operatively.

CONCLUSIONS

In the early post-operative period, PRAM provides reliable estimates of cardiac index and dp/dt(max) value compared with echocardiographic measurements. PRAM through mostcare^® is a reliable continuous monitoring method for peri-operative management in children with congenital heart disease.

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.

Comparison of three non-invasive hemodynamic monitoring methods in critically ill children

Introduction

Hemodynamic parameters measurements were widely conducted using pulmonary artery catheter (PAC) with thermodilution as a reference standard. Due to its technical difficulties in children, transthoracic echocardiography (TTE) has been widely employed instead. Nonetheless, TTE requires expertise and is time-consuming. Noninvasive cardiac output monitoring such as ultrasonic cardiac output monitor (USCOM) and electrical velocimetry (EV) can be performed rapidly with less expertise requirement. Presently, there are inconsistent evidences, variable precision, and reproducibility of EV, USCOM and TTE measurements. Our objective was to compare USCOM, EV and TTE in hemodynamic measurements in critically ill children.

Materials and methods

This was a single center, prospective observational study in critically ill children. Children with congenital heart diseases and unstable hemodynamics were excluded. Simultaneous measurements of hemodynamic parameters were conducted using USCOM, EV, and TTE. Inter-rater reliability was determined. Bland-Altman plots were used to analyse agreement of assessed parameters.

Results

Analysis was performed in 121 patients with mean age of 4.9 years old and 56.2% of male population. Interrater reliability showed acceptable agreement in all measured parameters (stroke volume (SV), cardiac output (CO), velocity time integral (VTI), inotropy (INO), flow time corrected (FTC), aortic valve diameter (AV), systemic vascular resistance (SVR), and stroke volume variation (SVV); (Cronbach’s alpha 0.76–0.98). Percentages of error in all parameters were acceptable by Bland-Altman analysis (9.2–28.8%) except SVR (30.8%) and SVV (257.1%).

Conclusion

Three noninvasive methods might be used interchangeably in pediatric critical care settings with stable hemodynamics. Interpretation of SVV and SVR measurements must be done with prudence.

Non-invasive measurement of cardiac output in children with repaired coarctation of the aorta using electrical cardiometry compared to transthoracic Doppler echocardiography

OBJECTIVE

To evaluate the equivalence of the ICON^® electrical cardiometry (EC) haemodynamic monitor to measure cardiac output (CO) relative to transthoracic Doppler echocardiography (TTE) in paediatric patients with repaired coarctation of the aorta (CoA).

APPROACH

A group of n  =  28 CoA patients and n  =  27 matched controls were enrolled. EC and TTE were performed synchronously on each participant and CO measurements compared using linear regression and Bland-Altman analysis. The CoA group was further subdivided into two groups, with n  =  10 and without n  =  18 increased left ventricular outflow tract velocity (iLVOTv) for comparison.

MAIN RESULTS

CO measurements from EC and TTE in controls showed a strong correlation (R  =  0.80, p  <  0.001) and an acceptable percentage error (PE) of 28.1%. However, combining CoA and control groups revealed a moderate correlation (R  =  0.57, p  <  0.001) and a poor PE (44.2%). We suspected that the CO in a subset of CoA participants with iLVOTv was overestimated by TTE. Excluding the iLVOTv CoA participants improved the correlation (R  =  0.77, p  <  0.001) and resulted in an acceptable PE of 31.2%.

SIGNIFICANCE

CO measurements in paediatric CoA patients in the absence of iLVOTv are clinically equivalent between EC and TTE. The presence of iLVOTv may impact the accuracy of CO measurement by TTE, but not EC.

Validation of capnodynamic determination of cardiac output by measuring effective pulmonary blood flow: a study in anaesthetised children and piglets

BACKGROUND

Effective pulmonary blood flow (CO_EPBF) has recently been validated as a technique for determining cardiac output (CO) in animals of varying sizes. The primary aim of our study was to investigate this new technique in paediatric surgical patients, compared with suprasternal two-dimensional Doppler (CO_SSD).

METHODS

A total of 15 children undergoing cleft lip/palate surgery were investigated. Before the start of surgery, manoeuvres that were anticipated to reduce (increase in PEEP from 3 to 10 cm H₂O) and increase (atropine) CO were undertaken. A study in mechanically ventilated piglets was also undertaken under general anaesthesia, measuring CO_EPBF and pulmonary artery (CO_TS) flow by ultrasonic probe as the comparator. Bias (Bland-Altman plots) and limits of agreement were assessed for effective pulmonary blood flow and CO_SSD or CO_TS.

RESULTS

In paediatric patients (median age 8.5 months), overall bias was -8.1 (limits of agreement -82 to +66) ml kg^-1 min^-1, with a mean percentage error of 48% and a concordance rate of 64%. In the piglet model, overall bias was -1 (-36 to +38) ml kg^-1 min^-1, with a mean percentage error of 31% and a concordance rate of 95%.

CONCLUSIONS

Under controlled experimental conditions, CO_EPBF is associated with excellent agreement and good trending ability when compared with the gold standard CO_TS. In the paediatric clinical setting, CO_EPBF performs well; by contrast, CO_SSD, an operator- and anatomy-dependent technology, appears less reliable than CO_EPBF.

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.

Centile Curves for Velocity-Time Integral Times Heart Rate as a Function of Ventricular Length: The Use of Minute Distance Is Advantageous to Enhance Clinical Reliability in Children

BACKGROUND

The generation of velocity-time integrals (VTIs) from Doppler signals is an essential component of standard echocardiographic investigations. The most effective algorithm to compensate for growth in children has, however, not yet been identified. This study was initiated to establish pediatric reference values for VTI and to enhance the interpretability of those values, considering technical and physiological factors.

METHODS

The echocardiographic data sets of healthy children and adolescents (N = 349; age range, 0-20 years) were recorded in a prospective approach and subsequently analyzed. In a pilot study, aortic and pulmonary VTIs were set in relation to the physiologic parameters of heart size as possible influencing parameters in a subgroup of children with comparable physical characteristics. The ratio with the smallest SD was taken as the base to generate centile curves using the LMS method. The clinical utility of the model was tested by examining patients (n = 80) with shunt lesions such as patent ductus arteriosus and atrial septal defect.

RESULTS

Feasibility was 94.6% for aortic VTI and 92.8% for pulmonary VTI. The pilot study identified ventricular length and heart rate as suitable parameters with the lowest relative SDs and high correlations with VTI. Gender differences were not relevant for children <7 years of age, and with increasing age, SD increased because of higher stroke volume variations. The detection of increased aortic VTI was possible with sensitivity of 73% for patients with patent ductus arteriosus with moderate or large hemodynamically significant ductus arteriosus. Patients with atrial septal defects with enlarged right ventricles could be identified as having increased pulmonary VTI with sensitivity of 84%.

CONCLUSIONS

These new reference values for VTI times heart rate as a function of ventricular length may be of specific clinical value to improve the assessment of cardiac function, therapeutic decision making, and follow-up in pediatric patients with heart disease.

Right and left ventricular function in hospitalized children with respiratory syncytial virus infection

Background

Extrapulmonary manifestations including cardiac dysfunction have been demonstrated in children with respiratory syncytial virus (RSV) infection requiring intensive care. The aim of this study was to examine cardiac function in hospitalized children with moderate RSV infection admitted to a regular pediatric ward.

Methods

We used echocardiography to determine cardiac output, and right and left ventricular function in 26 patients (aged 2 weeks to 24 months) with RSV infection. The echocardiographic results were compared with s-troponin, the need for supplementary oxygen or noninvasive respiratory support, and capillary refill time.

Results

The number of measured s-troponins (ten [38%] of the included children) was too low to assess differences between children with elevated levels and those with normal levels. There were no differences in cardiac function between patients receiving oxygen treatment or respiratory support and those who did not. Capillary refill time did not correlate with any of the echocardiographic parameters. Both left and right ventricular output (mL/kg/min) was higher than published reference values. All other echocardiographic parameters were within the reference range.

Conclusion

Children with moderate RSV infection had an increased left and right ventricular output, and cardiac function was well maintained. We conclude that routine cardiac ultrasound is not warranted in children with moderate RSV infection. The role of an elevated s-troponin in these patients remains to be determined.

In Vivo Intracardiac Vector Flow Imaging Using Phased Array Transducers for Pediatric Cardiology

Two-dimensional blood speckle tracking (ST) has shown promise for measuring complex flow patterns in neonatal hearts using linear arrays and high-frame-rate plane wave imaging. For general pediatric applications, however, the need for phased array probes emerges due to the limited intercostal acoustic window available. In this paper, a clinically approved real-time duplex imaging setup with phased array probes was used to investigate the potential of blood ST for the 2-D vector flow imaging of children with congenital heart disease. To investigate transmit beam pattern and tracking accuracy, straight tubes with parabolic flow were simulated at three depths (4.5, 7, and 9.5 cm). Due to the small aperture available, diffraction effects could be observed when approaching 10 cm, which limited the number of parallel receive beams that could be utilized. Moving to (slightly) diverging beams was shown to solve this issue at the expense of a loss in signal-to-noise ratio. To achieve consistent estimates, a forward-backward tracking scheme was introduced to avoid measurement bias occurring due to tracking kernel averaging artifacts at flow domain boundaries. Promising results were observed for depths <10 cm in two pediatric patients, where complex cardiac flow patterns could be estimated and visualized. As a loss in penetration compared with color flow imaging is expected, a larger clinical study is needed to establish the clinical feasibility of this approach.

Impedance cardiography in healthy children and children with congenital heart disease: Improving stroke volume assessment

INTRODUCTION

Stroke volume (SV) and cardiac output are important measures in the clinical evaluation of cardiac patients and are also frequently used in research applications. This study was aimed to improve SV scoring derived from spot-electrode based impedance cardiography (ICG) in a pediatric population of healthy volunteers and patients with a corrected congenital heart defect.

METHODS

128 healthy volunteers and 66 patients participated. First, scoring methods for ambiguous ICG signals were optimized to improve agreement of B- and X-points with aortic valve opening/closure in simultaneously recorded transthoracic echocardiography (TTE). Building on the improved scoring of B- and X-points, the Kubicek equation for SV estimation was optimized by testing the agreement with the simultaneously recorded SV by TTE. Both steps were initially done in a subset of the sample of healthy children and then validated in the remaining subset of healthy children and in a sample of patients.

RESULTS

SV assessment by ICG in healthy children strongly improved (intra class correlation increased from 0.26 to 0.72) after replacing baseline thorax impedance (Z₀) in the Kubicek equation by an equation (7.337-6.208∗dZ/dt_max), where dZ/dt_max is the amplitude of the ICG signal at the C-point. Reliable SV assessment remained more difficult in patients compared to healthy controls.

CONCLUSIONS

After proper adjustment of the Kubicek equation, SV assessed by the use of spot-electrode based ICG is comparable to that obtained from TTE. This approach is highly feasible in a pediatric population and can be used in an ambulatory setting.

Does obesity affect the non-invasive measurement of cardiac output performed by electrical cardiometry in children and adolescents?

Electrical cardiometry (EC) is a non-invasive and inexpensive method for hemodynamic assessment and monitoring. However, its feasibility for widespread clinical use, especially for the obese population, has yet to be determined. In this study, we evaluated the agreement and reliability of EC compared to transthoracic Doppler echocardiography (TTE) in normal, overweight, and obese children and adolescents. We measured stroke volume (SV) and cardiac output (CO) of 131 participants using EC and TTE simultaneously. We further divided these participants according to BMI percentiles for subanalyses: <85% normal weight (n = 41), between 85 and 95% overweight (n = 7), and >95% obese (n = 83). Due to small sample size of the overweight group, we combined overweight and obese groups (OW+OB) with no significant change in results (SV and CO) before and after combining groups. There were strong correlations between EC and TTE measurements of SV (r = 0.869 and r = 0.846; p < 0.0001) and CO (r = 0.831 and r = 0.815; p < 0.0001) in normal and OW+OB groups, respectively. Bias and percentage error for CO measurements were 0.240 and 29.7%, and 0.042 and 29.5% in the normal and OW+OB groups, respectively. Indexed values for SV were lower in the OW+OB group than in the normal weight group when measured by EC (p < 0.0001) but no differences were seen when measured by TTE (p = 0.096). In all weight groups, there were strong correlations and good agreement between EC and TTE. However, EC may underestimate hemodynamic measurements in obese participants due to fat tissue.

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.

Electrical Cardiometry to Monitor Cardiac Output in Preterm Infants with Patent Ductus Arteriosus: A Comparison with Echocardiography

BACKGROUND

Electrical cardiometry (EC) is an impedance-based monitoring that provides noninvasive cardiac output (CO) assessment. Through comparison to transthoracic echocardiography (Echo), the accuracy of EC has been verified. However, left-to-right patent ductus arteriosus (PDA) shunting is a concern because PDA shunts aortic flow to the pulmonary artery and may interfere with EC in measuring CO.

OBJECTIVE

To determine the agreement between EC and Echo in preterm infants with a hemodynamically significant PDA (hsPDA).

METHODS

We reviewed our hemodynamic database in which simultaneous CO measurements by Echo and EC (Aesculon®) were recorded. Preterm infants with left-to-right shunting hsPDA were enrolled.

RESULTS

A total of 105 paired measurements in 36 preterm infants were compared. Infants' median (range) age and weight at measurement were 27+2 weeks (24+0-33+1) and 1,015 g (518-1,880), with mean (95% CI) ductal diameter 2.11 mm (1.99-2.22) or 2.15 mm/kg (2.00-2.30). Mean COEC and COEcho were 252 ± 32 and 258 ± 45 mL/kg/min, respectively, which demonstrated a moderate correlation and without a significant between-measurement difference. Bland-Altman analysis showed a bias, limits of agreement, and error percentage of -5.3 mL/kg/min, -78.3 to 67.7 mL/kg/min, and 28.6%, respectively. There was a trend of increased bias and error percentage of infants with high CO ≥280 mL/kg/min and supported with high-frequency ventilator.

CONCLUSIONS

EC and Echo have a wide but clinically acceptable agreement in measuring CO in preterm infants with hsPDA. However, for infants with high CO or ventilated by high-frequency ventilation, interpretation of COEC should be approached with caution.

Assessing the Performance of Ultrafast Vector Flow Imaging in the Neonatal Heart via Multiphysics Modeling and In Vitro Experiments

Ultrafast vector flow imaging would benefit newborn patients with congenital heart disorders, but still requires thorough validation before translation to clinical practice. This paper investigates 2-D speckle tracking (ST) of intraventricular blood flow in neonates when transmitting diverging waves at ultrafast frame rate. Computational and in vitro studies enabled us to quantify the performance and identify artifacts related to the flow and the imaging sequence. First, synthetic ultrasound images of a neonate's left ventricular flow pattern were obtained with the ultrasound simulator Field II by propagating point scatterers according to 3-D intraventricular flow fields obtained with computational fluid dynamics (CFD). Noncompounded diverging waves (opening angle of 60°) were transmitted at a pulse repetition frequency of 9 kHz. ST of the B-mode data provided 2-D flow estimates at 180 Hz, which were compared with the CFD flow field. We demonstrated that the diastolic inflow jet showed a strong bias in the lateral velocity estimates at the edges of the jet, as confirmed by additional in vitro tests on a jet flow phantom. Furthermore, ST performance was highly dependent on the cardiac phase with low flows (<5 cm/s), high spatial flow gradients, and out-of-plane flow as deteriorating factors. Despite the observed artifacts, a good overall performance of 2-D ST was obtained with a median magnitude underestimation and angular deviation of, respectively, 28% and 13.5° during systole and 16% and 10.5° during diastole.

Effect of patent ductus arteriosus and patent foramen ovale on left ventricular stroke volume measurement by electrical velocimetry in comparison to transthoracic echocardiography in neonates

This prospective single-center observational study compared impedance cardiography [electrical velocimetry (EV)] with transthoracic echocardiography (TTE, based on trans-aortic flow) and analyzed the influence of physiological shunts, such as patent ductus arteriosus (PDA) or patent foramen ovale (PFO), on measurement accuracy. Two hundred and ninety-one triplicate simultaneous paired left ventricular stroke volume (LVSV) measurements by EV (LVSV_EV) and TTE (LVSV_TTE) in 99 spontaneously breathing neonates (mean weight 3270 g; range 1227-4600 g) were included. For the whole cohort, the mean absolute LVSV_EV was 5.5 mL, mean LVSV_TTE was 4.9 mL, resulting in an absolute Bland-Altman bias of -0.7 mL (limits of agreement LOA -3.0 to 1.7 mL), relative bias -12.8 %; mean percentage error MPE 44.9 %; true precision TP_EV 33.4 % (n = 99 aggregated data points). In neonates without shunts (n = 32): mean LVSV_EV 5.0 mL, mean LVSV_TTE 4.6 mL, Bland-Altman bias -0.4 mL (LOA -2.8 to 2.0 mL), relative bias -8.2 %; MPE 50.7 %; TP_EV 40.9 %. In neonates with shunts (PDA and/or PFO; n = 67): mean LVSV_EV 5.8 mL, mean LVSV_TTE 5.0 mL, bias -0.8 mL (LOA -3.1 to 1.5 mL), relative bias -14.8 %, MPE 41.9 %, TP_EV 29.3 %. Accuracy was affected by PDA and/or PFO, with a significant increase in the relative difference in LVSV_EV versus LVSV_TTE: Subjects without shunts -2.9 % (n = 91), PFO alone -9.6 % (n = 125), PDA alone -14.0 % (n = 12), and PDA and PFO -18.5 % (n = 63). Physiological shunts (PDA and/or PFO) in neonates affect measurement accuracy and cause overestimation of LVSV_EV compared with LVSV_TTE.

Respiratory variation in aortic blood flow peak velocity to predict fluid responsiveness in mechanically ventilated children: a systematic review and meta-analysis

BACKGROUND

Dynamic indices of preload have been shown to better predict fluid responsiveness than static variables in mechanically ventilated adults. In children, dynamic predictors of fluid responsiveness have not yet been extensively studied.

AIM

To evaluate the diagnostic accuracy of respiratory variation in aortic blood flow peak velocity (ΔVPeak) for the prediction of fluid responsiveness in mechanically ventilated children.

METHOD

PubMed, Embase, and the Cochrane Database of Systematic Reviews were screened for studies relevant to the use of ΔVPeak to predict fluid responsiveness in children receiving mechanical ventilation. Clinical trials published as full-text articles in indexed journals without language restriction were included. We calculated the pooled values of sensitivity, specificity, diagnostic odds ratio (DOR), and positive and negative likelihood ratio using a random-effects model.

RESULTS

In total, six studies (163 participants) met the inclusion criteria. Data are reported as point estimate with 95% confidence interval. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and DOR of ΔVPeak to predict fluid responsiveness for the overall population were 92.0% (84.1-96.7), 85.5% (75.6-92.5), 4.89 (2.92-8.18), 0.13 (0.07-0.25), and 50.44 (17.70-143.74), respectively. The area under the summary receiver operating characteristic curve was 0.94. Cutoff values for ΔVPeak to predict fluid responsiveness varied across studies, ranging from 7% to 20%.

CONCLUSION

Our results confirm that the ΔVPeak is an accurate predictor of fluid responsiveness in children under mechanical ventilation. However, the question of the optimal cutoff value of ΔVPeak to predict fluid responsiveness remains uncertain, as there are important variations between original publications, and needs to be resolved in further studies. The potential impact of intraoperative cardiac output optimization using goal-directed fluid therapy based on ΔVPeak on the perioperative outcome in the pediatric population should be subsequently evaluated.

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.

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.

Noninvasive cardiac output measurement using bioreactance in postoperative pediatric patients

BACKGROUND

Thoracic bioreactance is a noninvasive and continuous method of cardiac output (CO) measurement that is being developed in adult patients. Very little information is available on thoracic bioreactance use in children.

OBJECTIVE

The aim of the study was to evaluate the ability of a bioreactance device (NICOM(®) ; Cheetah Medical, Tel Aviv, Israel) to estimate CO and to track changes in CO induced by volume expansion (VE) in children.

METHODS

Cardiac output values obtained using the NICOM(®) device (CONICOM ) and measured by trans-thoracic echocardiography (COTTE ) were compared in pediatric neurosurgical patients during the postoperative period.

RESULTS

Seventy-three pairs of measurements of CO obtained in 30 children were available for analysis. The bias (lower and upper limits of agreement) between CONICOM and COTTE was -0.11 (-1.4 to 1.2) l·min(-1). The percentage error (PE) was 55%. The precision of the NICOM(®) device was 45%. A significant correlation was observed between the CO values obtained using the two methods (r = 0.89, <0.001). The concordance percentage between changes in COTTE and CON icom induced by VE was 84% following exclusion of patients with changes in CO <15% (n = 5).

CONCLUSIONS

The PE observed is too large, and the limits of agreement too wide, to enable us to comment on the equivalence of the two techniques of CO measurements. However, the NICOM(®) device performs well in tracking changes in CO following VE.

Impedance cardiography (electrical velocimetry) and transthoracic echocardiography for non-invasive cardiac output monitoring in pediatric intensive care patients: a prospective single-center observational study

Introduction

Electrical velocimetry (EV) is a type of impedance cardiography, and is a non-invasive and continuously applicable method of cardiac output monitoring. Transthoracic echocardiography (TTE) is non-invasive but discontinuous.

Methods

We compared EV with TTE in pediatric intensive care patients in a prospective single-center observational study. Simultaneous, coupled, left ventricular stroke volume measurements were performed by EV using an Aesculon® monitor and TTE (either via trans-aortic valve flow velocity time integral [EVVTI], or via M-mode [EVMM]). H₀: bias was less than 10% and the mean percentage error (MPE) was less than 30% in Bland–Altman analysis between EV and TTE. If appropriate, data were logarithmically transformed prior to Bland–Altman analysis.

Results

A total of 72 patients (age: 2 days to 17 years; weight: 0.8 to 86 kg) were analyzed. Patients were divided into subgroups: organ transplantation (OTX, n =28), sepsis or organ failure (SEPSIS, n =16), neurological patients (NEURO, n =9), and preterm infants (PREM, n =26); Bias/MPE for EVVTI was 7.81%/26.16%. In the EVVTI subgroup analysis for OTX, NEURO, and SEPSIS, bias and MPE were within the limits of H₀, whereas the PREM subgroup had a bias/MPE of 39.00%/46.27%. Bias/MPE for EVMM was 8.07%/37.26% where the OTX and NEURO subgroups were within the range of H₀, but the PREM and SEPSIS subgroups were outside the range. Mechanical ventilation, non-invasive continuous positive airway pressure ventilation, body weight, and secondary abdominal closure were factors that significantly affected comparison of the methods.

Conclusions

This study shows that EV is comparable with aortic flow-based TTE for pediatric patients.

Stroke volume variation and indexed stroke volume measured using bioreactance predict fluid responsiveness in postoperative children

BACKGROUND

Postoperative fluid management can be challenging in children after haemorrhagic surgery. The goal of this study was to assess the ability of dynamic cardiovascular variables measured using bioreactance (NICOM®, Cheetah Medical, Tel Aviv, Israel) to predict fluid responsiveness in postoperative children.

METHODS

Children sedated and mechanically ventilated, who require volume expansion (VE) during the immediate postoperative period, were included. Indexed stroke volume (SVi), cardiac index, and stroke volume variation (SVV) were measured using the NICOM® device. Responders (Rs) to VE were patients showing an increase in SV measured using transthoracic echocardiography of at least 15% after VE. Data are median [95% confidence interval (CI)].

RESULTS

Thirty-one patients were included, but one patient was excluded because of the lack of calibration of the NICOM® device. Before VE, SVi [33 (95% CI 31-36) vs 24 (95% CI 21-28) ml m(-2); P=0.006] and SVV [8 (95% CI 4-11) vs 13 (95% CI 11-15)%; P=0.004] were significantly different between non-responders and Rs. The areas under the receiver operating characteristic curves of SVi and SVV for predicting fluid responsiveness were 0.88 (95% CI 0.71-0.97) and 0.81 (95% CI 0.66-0.96), for a cut-off value of 29 ml m(-2) (grey zone 27-29 ml m(-2)) and 10% (grey zone 9-15%), respectively.

CONCLUSIONS

The results of this study show that SVi and SVV non-invasively measured by bioreactance are predictive of fluid responsiveness in sedated and mechanically ventilated children after surgery.

Cardiovascular magnetic resonance of cardiac function and myocardial mass in preterm infants: a preliminary study of the impact of patent ductus arteriosus

BACKGROUND

Many pathologies seen in the preterm population are associated with abnormal blood supply, yet robust evaluation of preterm cardiac function is scarce and consequently normative ranges in this population are limited. The aim of this study was to quantify and validate left ventricular dimension and function in preterm infants using cardiovascular magnetic resonance (CMR). An initial investigation of the impact of the common congenital defect patent ductus arteriosus (PDA) was then carried out.

METHODS

Steady State Free Procession short axis stacks were acquired. Normative ranges of left ventricular end diastolic volume (EDV), stroke volume (SV), left ventricular output (LVO), ejection fraction (EF), left ventricular (LV) mass, wall thickness and fractional thickening were determined in "healthy" (control) neonates. Left ventricular parameters were then investigated in PDA infants. Unpaired student t-tests compared the 2 groups. Multiple linear regression analysis assessed impact of shunt volume in PDA infants, p-value ≤ 0.05 being significant.

RESULTS

29 control infants median (range) corrected gestational age at scan 34+6(31+1-39+3) weeks were scanned. EDV, SV, LVO, LV mass normalized by weight and EF were shown to decrease with increasing corrected gestational age (cGA) in controls. In 16 PDA infants (cGA 30+3(27+3-36+1) weeks) left ventricular dimension and output were significantly increased, yet there was no significant difference in ejection fraction and fractional thickening between the two groups. A significant association between shunt volume and increased left ventricular mass correcting for postnatal age and corrected gestational age existed.

CONCLUSION

CMR assessment of left ventricular function has been validated in neonates, providing more robust normative ranges of left ventricular dimension and function in this population. Initial investigation of PDA infants would suggest that function is relatively maintained.