Advances in Point-of-Care Ultrasound in Pediatric Acute Care Medicine.

Pediatric point-of-care ultrasonography (POCUS) has grown in utilization and is now an integral part of pediatric acute care. Applications within the pediatric critical care, neonatology and pediatric emergency were once limited to evaluation of undifferentiated shock states, abdominal free fluid assessments in trauma resuscitation and procedural guidance. The body of pediatric POCUS literature is ever expanding and recently published international consensus guidelines are available to guide implementation into clinical practice. The authors present a review of emerging applications and controversies within thoracic, hemodynamic, neurologic, and ocular POCUS in pediatric acute care medicine.

Ultrasound in Cardiopulmonary Arrest and Resuscitation: Constructing Comprehensive Implementation Frameworks in High-Risk Settings.

OBJECTIVES: Information obtained from point-of-care ultrasound during cardiopulmonary arrest and resuscitation (POCUS-CA) can be used to identify underlying pathophysiology and provide life-sustaining interventions. However, integration of POCUS-CA into resuscitation care is inconsistent. We used expert consensus building methodology to help identify discrete barriers to clinical integration. We subsequently applied implementation science frameworks to generate generalizable strategies to overcome these barriers. MEASURES AND MAIN RESULTS: Two multidisciplinary expert working groups used KJ Reverse-Merlin consensus building method to identify and characterize barriers contributing to failed POCUS-CA utilization in a hypothetical future state. Identified barriers were organized into affinity groups. The Center for Implementation Research (CFIR) framework and Expert Recommendations for Implementing Change (CFIR-ERIC) tool were used to identify strategies to guide POCUS-US implementation. RESULTS: Sixteen multidisciplinary resuscitation content experts participated in the working groups and identified individual barriers, consolidated into 19 unique affinity groups that mapped 12 separate CFIR constructs, representing all 5 CFIR domains. The CFIR-ERIC tool identified the following strategies as most impactful to address barriers described in the affinity groups: identify and prepare champions, conduct local needs assessment, conduct local consensus discussions, and conduct educational meetings. CONCLUSIONS: KJ Reverse-Merlin consensus building identified multiple barriers to implementing POCUS-CA. Implementation science methodologies identified and prioritized strategies to overcome barriers and guide POCUS-CA implementation across diverse clinical settings.

Cardiac point-of-care ultrasound: Practical integration in the pediatric and neonatal intensive care settings.

Cardiac point-of-care ultrasound (POCUS) is a technology increasingly leveraged at the bedside by pediatric critical care and neonatology providers to identify real-time hemodynamic pathophysiology. We present a framework for (1) identifying the scope of cardiac POCUS within the clinical practice setting, (2) standardizing views for protocolized hemodynamic assessment relevant to pediatric critical illness and (3) integrating POCUS findings for therapeutic guidance. Within the review, we also discuss practical strengths and limitations to image acquisition and interpretation within the varied cardiac POCUS views. Finally, we explore unique considerations within the neonatal population.    Conclusion: Cardiac POCUS is a technology and tool that reveals important real-time information at the bedside of the critically ill child and infant. Understanding strengths and limitations of cardiac POCUS views and protocolizing an approach to answer focused clinical questions provides a framework for training and translation to clinical care. What is Known: • Ultrasound technology is now ubiquitous among pediatric critical care and neonatology settings, and growing literature supports an expanded role in not only procedural but also diagnostic applications. • Cardiac POCUS influences provider perception of pathophysiology and changes clinical management. What is New: • Effective cardiac POCUS training and subsequent translation to clinical practice should improve when clinical questions and protocolized approaches to image acquisition are standardized within a specialty. • Cardiac POCUS views have strengths and limitations which must be recognized when assessing the hemodynamic profile of a child or neonate.

Ultrasound assessment of diaphragm thickness, contractility, and strain in healthy pediatric patients.

BACKGROUND: Ultrasound-based diaphragmatic assessments are becoming more common in pediatric acute care, but baseline pediatric diaphragm thickness and contractility values remain unknown. METHODS: We conducted a prospective, observational study of healthy children aged <18 years undergoing elective surgery. Diaphragm thickness at end-expiration (Tdi-exp), thickening fraction (DTF) and excursion were measured by ultrasound during spontaneous breathing and during mechanical ventilation. Diaphragm strain and peak strain rate were ascertained post hoc. Measurements were compared across a priori specified age groups (<1 year, 1 to <3, 3 to <6, 6 to <12, and 12 to <18 years) and with versus without mechanical ventilation. RESULTS: Fifty subjects were evaluated (n = 10 per age group). Baseline mean Tdi-exp was 0.19 ± 0.04 cm, DTF 0.19 ± 0.09, excursion 1.69 ± 0.97 cm, strain -10.3 ± 4.9, peak strain rate -0.48 ± 0.21 s-1 . No significant difference in Tdi-exp or DTF was observed across age groups (p > .05). Diaphragm excursion increased with age (p < .0001). Diaphragm strain was significantly greater in the 12-17-year age group (-14.3 ± 6.4), p = .048, but there were no age-related differences in peak strain rate (p = .08). During mechanical ventilation, there were significant decreases in DTF 0.12 ± 0.04 (p < .0001), excursion 1.08 ± 0.31 cm (p < .0001), strain -4.60 ± 1.93 (p < .0001), and peak strain rate -0.20 ± 0.10 s-1 (p < .0001) while there was no change in Tdi-exp 0.18 ± 0.03 cm (p = .25) when compared to baseline values. CONCLUSION: Pediatric Tdi-exp, DTF, and diaphragm peak strain rate were similar across age groups. Diaphragm excursion and strain varied across age groups. All measures of diaphragm contractility were diminished during mechanical ventilation.

Identifying commonalities in definition and governance of point-of-care ultrasound within statements from medical organizations in the United States: A scoping review for a shared understanding.

This scoping review analyzed statements from 22 medical organizations in the United States to identify commonalities in the definition and governance of point-of-care ultrasound (POCUS). A total of 41 statements were included. The review found that the most commonly used elements in defining POCUS were "focused," "bedside," and "patient care." In terms of governance, consistent requirements included specific training programs, documentation in medical records, continuous quality assurance, and standards for credentialing and privileging. These findings suggest the existence of essential commonalities that could facilitate communication and the development of standardized POCUS programs in the future.

Impaired echocardiographic left ventricular global longitudinal strain after pediatric cardiac arrest children is associated with mortality.

BACKGROUND: Global longitudinal strain (GLS) is an echocardiographic method to identify left ventricular (LV) dysfunction after cardiac arrest that is less sensitive to loading conditions. We aimed to identify the frequency of impaired GLS following pediatric cardiac arrest, and its association with hospital mortality. METHODS: This is a retrospective single-center cohort study of children <18 years of age treated in the pediatric intensive care unit (PICU) after in- or out-of-hospital cardiac arrest (IHCA and OHCA), with echocardiogram performed within 24 hours of initiation of post-arrest PICU care between 2013 and 2020. Patients with congenital heart disease, post-arrest extracorporeal support, or inability to measure GLS were excluded. Echocardiographic LV ejection fraction (EF) and shortening fraction (SF) were abstracted from the chart. GLS was measured post hoc; impaired strain was defined as LV GLS ≥ 2 SD worse than age-dependent normative values. Demographics and pre-arrest, arrest, and post-arrest characteristics were compared between subjects with normal versus impaired GLS. Correlation between GLS, SF and EF were calculated with Pearson comparison. Logistic regression tested the association of GLS with mortality. Area under the receiver operator curve (AUROC) was calculated for discriminative utility of GLS, EF, and SF with mortality. RESULTS: GLS was measured in 124 subjects; impaired GLS was present in 46 (37.1%). Subjects with impaired GLS were older (median 7.9 vs. 1.9 years, p < 0.001), more likely to have ventricular tachycardia/fibrillation as initial rhythm (19.6% versus 3.8%, p = 0.017) and had higher peak troponin levels in the first 24 hours post-arrest (median 2.5 vs. 0.5, p = 0.002). There were no differences between arrest location or CPR duration by GLS groups. Subjects with impaired GLS compared to normal GLS had lower median EF (42.6% versus 62.3%) and median SF (23.3% versus 36.6%), all p < 0.001, with strong inverse correlation between GLS and EF (rho -0.76, p < 0.001) and SF (rho -0.71, p < 0.001). Patients with impaired GLS had higher rates of mortality (60% vs. 32%, p = 0.009). GLS was associated with mortality when controlling for age and initial rhythm [aOR 1.17 per 1% increase in GLS (95% CI 1.09-1.26), p < 0.001]. GLS, EF and SF had similar discrimination for mortality: GLS AUROC 0.69 (95% CI 0.60-0.79); EF AUROC 0.71 (95% CI 0.58-0.88); SF AUROC 0.71 (95% CI 0.61-0.82), p = 0.101. CONCLUSIONS: Impaired LV function as measured by GLS after pediatric cardiac arrest is associated with hospital mortality. GLS is a novel complementary metric to traditional post-arrest echocardiography that correlates strongly with EF and SF and is associated with mortality. Future large prospective studies of post-cardiac arrest care should investigate the prognostic utilities of GLS, alongside SF and EF.

Contemporary Use of Ultrasonography in Acute Care Pediatrics.

Use of ultrasonography by clinicians at the point of care has expanded widely and rapidly. Pediatric acute care providers now leverage this valuable tool to guide procedures, diagnose pathophysiologic processes, and inform time-sensitive decisions in sick and unstable children. However, the deployment of any new technology must be packaged with training, protocols, and safeguards to optimize safety for patients, providers, and institutions. As ultrasonography is increasingly incorporated into residency, fellowship, and even medical student curricula, it is important that educators and trainees are aware of the diversity of its clinical applications. This article aims to review the current state of point-of-care ultrasonography in acute care pediatrics, with an emphasis on the literature supporting the use of this important clinical tool.

The association between carotid flow time and fluid responsiveness in children under general anesthesia.

BACKGROUND: Fluid administration in children undergoing surgery requires precision, however, determining fluid responsiveness can be challenging. Ultrasound has been used widely in the emergency department and intensive care units as a noninvasive, bedside manner of determining volume status, but the intraoperative period presents unique challenges as often the chest and abdomen are inaccessible for ultrasound. We investigate whether carotid artery ultrasound, specifically carotid flow time, can be used to determine fluid responsiveness in children under general anesthesia. METHODS: Prospective observational study of 87 children ages 1-12 years who were scheduled for elective noncardiac surgery. Ultrasound of the carotid artery and heart was performed at three time points: (1) after inhalational induction of anesthesia with the subject spontaneously breathing, (2) during positive pressure ventilation through endotracheal tube or supraglottic airway with tidal volume set at 8 ml/kg with PEEP of 10 cmH2 O, and (3) after a 10 ml/kg fluid bolus. Carotid flow time and cardiac output were measured from saved images. RESULTS: Corrected carotid flow time (FTc) increased with initiation of positive pressure ventilation in both fluid responders and nonresponders (352.7 vs. 365.3 msec, p = .005 in fluid responders; 348.3 vs. 365.2 msec, p = .001 in nonresponders). FTc increased after fluid bolus in both responders and nonresponders (365.3 vs. 397.6 msec, p < .001 in fluid responders; 365.2 vs. 397.2 msec, p < .001 in nonresponders). However, baseline FTc during spontaneous ventilation or positive pressure ventilation prior to fluid bolus was not associated with fluid responsiveness. DISCUSSION: Flow time increases with initiation of positive pressure ventilation and after administration of a fluid bolus. FTc may serve as an indicator of fluid status but does not predict fluid responsiveness in children under general anesthesia.

Establishing a risk assessment framework for point-of-care ultrasound.

Point-of-care ultrasound (POCUS) refers to the use of portable ultrasound (US) applications at the bedside, performed directly by the treating physician, for either diagnostic or procedure guidance purposes. It is being rapidly adopted by traditionally non-imaging medical specialties across the globe. Recent international evidence-based guidelines on POCUS for critically ill neonates and children were issued by the POCUS Working Group of the European Society of Pediatric and Neonatal Intensive Care (ESPNIC). Currently there are no standardized national or international guidelines for its implementation into clinical practice or even the training curriculum to monitor quality assurance. Further, there are no definitions or methods of POCUS competency measurement across its varied clinical applications. CONCLUSION: The Hippocratic Oath suggests medical providers do no harm to their patients. In our continued quest to uphold this value, providers seeking solutions to clinical problems must often weigh the benefit of an intervention with the risk of harm to the patient. Technologies to guide diagnosis and medical management present unique considerations when assessing possible risk to the patient. Frequently risk extends beyond the patient and impacts providers and the institutions in which they practice. POCUS is an emerging technology increasingly incorporated in the care of children across varied clinical specialties. Concerns have been raised by clinical colleagues and regulatory agencies regarding appropriate POCUS use and oversight. We present a framework for assessing the risk of POCUS use in pediatrics and suggest methods of mitigating risk to optimize safety and outcomes for patients, providers, and institutions. WHAT IS KNOWN: • The use POCUS by traditionally non-imaging pediatric specialty physicians for both diagnostic and procedural guidance is rapidly increasing. • Although there are international guidelines for its indications, currently there is no standardized guidance on its implementation in clinical practice. WHAT IS NEW: • Although standards for pediatric specialty-specific POCUS curriculum and training to competency have not been defined, POCUS is likely to be most successfully incorporated in clinical care when programmatic infrastructural elements are present. • Risk assessment is a forward-thinking process and requires an imprecise calculus that integrates considerations of the technology, the provider, and the context in which medical care is delivered. Medicolegal considerations vary across countries and frequently change, requiring providers and institutions to understand local regulatory requirements and legal frameworks to mitigate the potential risks of POCUS.

A Call to Action for the Pediatric Critical Care Community.

Healthcare regulatory bodies have escalated concerns regarding the use of point-of-care ultrasound by nonradiology and noncardiology physicians. A recently published PCCMPerspective identified that data do not support many of these concerns and addressed common misconceptions associated with point-of-care ultrasound use in the critical care setting. Indeed, the global point-of-care ultrasound community and specifically the pediatric critical care community have the opportunity to be leaders in demonstrating how to translate new skills and technologies to the bedside in a safe and effective manner. We seek to extend the conversation and propose next steps in supporting integration of point-of-care ultrasound in pediatric critical care practice.

Integrating Focused Cardiac Ultrasound Into Pediatric Septic Shock Assessment.

OBJECTIVES: To assess focused cardiac ultrasound impact on clinician hemodynamic characterization of patients with suspected septic shock as well as expert-generated focused cardiac ultrasound algorithm performance. DESIGN: Retrospective, observational study. SETTING: Single-center, noncardiac PICU. PATIENTS: Less than 18 years old receiving focused cardiac ultrasound study within 72 hours of sepsis pathway initiation from January 2014 to December 2016. INTERVENTIONS: Hemodynamics of patients with suspected septic shock were characterized as fluid responsive, myocardial dysfunction, obstructive physiology, and/or reduced systemic vascular resistance by a bedside clinician before and immediately following focused cardiac ultrasound performance. The clinician's post-focused cardiac ultrasound hemodynamic assessments were compared with an expert-derived focused cardiac ultrasound algorithmic hemodynamic interpretation. Subsequent clinical management was assessed for alignment with focused cardiac ultrasound characterization and association with patient outcomes. MEASUREMENTS AND MAIN RESULTS: Seventy-one patients with suspected septic shock (median, 4.7 yr; interquartile range, 1.6-8.1) received clinician performed focused cardiac ultrasound study within 72 hours of sepsis pathway initiation (median, 2.1 hr; interquartile range, -1.5 to 11.8 hr). Two patients did not have pre-focused cardiac ultrasound and 23 patients did not have post-focused cardiac ultrasound hemodynamic characterization by clinicians resulting in exclusion from related analyses. Post-focused cardiac ultrasound clinician hemodynamic characterization differed from pre-focused cardiac ultrasound characterization in 67% of patients (31/46). There was substantial concordance between clinician's post-focused cardiac ultrasound and algorithm hemodynamic characterization (33/48; κ = 0.66; CI, 0.51-0.80). Fluid responsive (κ = 0.62; CI, 0.40-0.84), obstructive physiology (к = 0.87; CI, 0.64-1.00), and myocardial dysfunction (1.00; CI, 1.00-1.00) demonstrated substantial to perfect concordance. Management within 4 hours of focused cardiac ultrasound aligned with algorithm characterization in 53 of 71 patients (75%). Patients with aligned management were less likely to have a complicated course (14/52, 27%) compared with misaligned management (8/19, 42%; p = 0.25). CONCLUSIONS: Incorporation of focused cardiac ultrasound in the evaluation of patients with suspected septic shock frequently changed a clinician's characterization of hemodynamics. An expert-developed algorithm had substantial concordance with a clinician's post-focused cardiac ultrasound hemodynamic characterization. Management aligned with algorithm characterization may improve outcomes in children with suspected septic shock.

Clinical Signs to Categorize Shock and Target Vasoactive Medications in Warm Versus Cold Pediatric Septic Shock.

OBJECTIVES: Determine level of agreement among clinical signs of shock type, identify which signs clinicians prioritize to determine shock type and select vasoactive medications, and test the association of shock type-vasoactive mismatch with prolonged organ dysfunction or death (complicated course). DESIGN: Retrospective observational study. SETTING: Single large academic PICU. PATIENTS: Patients less than 18 years treated on a critical care sepsis pathway between 2012 and 2016. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Agreement among clinical signs (extremity temperature, capillary refill, pulse strength, pulse pressure, and diastolic blood pressure) was measured using Fleiss and Cohen's κ. Association of clinical signs with shock type and shock type-vasoactive mismatch (e.g., cold shock treated with vasopressor rather than inotrope) with complicated course was determined using multivariable logistic regression. Of 469 patients, clinicians determined 307 (65%) had warm and 162 (35%) had cold shock. Agreement across all clinical signs was low (κ, 0.25; 95% CI, 0.20-0.30), although agreement between extremity temperature, capillary refill, and pulse strength was better than with pulse pressure and diastolic blood pressure. Only extremity temperature (adjusted odds ratio, 26.6; 95% CI, 15.5-45.8), capillary refill (adjusted odds ratio, 15.7; 95% CI, 7.9-31.3), and pulse strength (adjusted odds ratio, 21.3; 95% CI, 8.6-52.7) were associated with clinician-documented shock type. Of the 86 patients initiated on vasoactive medications during the pathway, shock type was discordant from vasoactive medication (κ, 0.14; 95% CI, -0.03 to 0.31) and shock type-vasoactive mismatch was not associated with complicated course (adjusted odds ratio, 0.3; 95% CI, 0.1-1.02). CONCLUSIONS: Agreement was low among common clinical signs used to characterize shock type, with clinicians prioritizing extremity temperature, capillary refill, and pulse strength. Although clinician-assigned shock type was often discordant with vasoactive choice, shock type-vasoactive mismatch was not associated with complicated course. Categorizing shock based on clinical signs should be done cautiously.

Diaphragm Atrophy During Pediatric Acute Respiratory Failure Is Associated With Prolonged Noninvasive Ventilation Requirement Following Extubation.

OBJECTIVES: Diaphragm atrophy is evident during invasive ventilation for pediatric acute respiratory failure, but with unknown significance. We hypothesized that diaphragm atrophy in pediatric acute respiratory failure is associated with prolonged noninvasive positive pressure ventilation following extubation. DESIGN: Prospective observational study. SETTING: Single-center academic PICU. PATIENTS: Invasively ventilated children with acute respiratory failure. INTERVENTIONS: Diaphragm ultrasound was performed within 36 hours after intubation and repeated within 48 hours preceding extubation. Rapid shallow breathing index at 15 and 30 minutes of a spontaneous breathing trial and negative inspiratory force were collected in a subset of patients concurrently with the ultrasound measurements. MEASUREMENTS AND MAIN RESULTS: Diaphragm thickness at end-expiration was measured to assess for diaphragm atrophy during mechanical ventilation. Percentage change in diaphragm thickness at end-expiration was defined as baseline diaphragm thickness at end-expiration minus final, preextubation diaphragm thickness at end-expiration divided by baseline diaphragm thickness at end-expiration. The primary outcome measure was duration of noninvasive positive pressure ventilation following extubation with prolonged use defined as noninvasive positive pressure ventilation use for greater than 24 hours postextubation. Among 56 children, 47 (median age, 15.5 mo; interquartile range, 6-53 mo) had diaphragm thickness at end-expiration measured within 48 hours prior to extubation. Fourteen (30%) had prolonged noninvasive positive pressure ventilation use with median duration 110 hours (interquartile range, 52-130 hr). The median percentage change of diaphragm thickness at end-expiration from baseline among those with and without prolonged noninvasive positive pressure ventilation use was -20% (interquartile range, -32% to -10%) versus -7% (interquartile range, -21% to 0%) (p = 0.04). CONCLUSIONS: Diaphragm atrophy is associated with prolonged postextubation noninvasive positive pressure ventilation in children with acute respiratory failure. Serial bedside diaphragm ultrasound may identify children at risk for prolonged noninvasive positive pressure ventilation use after extubation.

International evidence-based guidelines on Point of Care Ultrasound (POCUS) for critically ill neonates and children issued by the POCUS Working Group of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC).

BACKGROUND: Point-of-care ultrasound (POCUS) is nowadays an essential tool in critical care. Its role seems more important in neonates and children where other monitoring techniques may be unavailable. POCUS Working Group of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC) aimed to provide evidence-based clinical guidelines for the use of POCUS in critically ill neonates and children. METHODS: Creation of an international Euro-American panel of paediatric and neonatal intensivists expert in POCUS and systematic review of relevant literature. A literature search was performed, and the level of evidence was assessed according to a GRADE method. Recommendations were developed through discussions managed following a Quaker-based consensus technique and evaluating appropriateness using a modified blind RAND/UCLA voting method. AGREE statement was followed to prepare this document. RESULTS: Panellists agreed on 39 out of 41 recommendations for the use of cardiac, lung, vascular, cerebral and abdominal POCUS in critically ill neonates and children. Recommendations were mostly (28 out of 39) based on moderate quality of evidence (B and C). CONCLUSIONS: Evidence-based guidelines for the use of POCUS in critically ill neonates and children are now available. They will be useful to optimise the use of POCUS, training programs and further research, which are urgently needed given the weak quality of evidence available.

Seeing Is Believing: Ultrasound in Pediatric Procedural Performance.

Point-of-care ultrasound is currently widely used across the landscape of pediatric care. Ultrasound machines are now smaller, are easier to use, and have much improved image quality. They have become common in emergency departments, ICUs, inpatient wards, and outpatient clinics. Recent growth of supportive evidence makes a strong case for using point-of-care ultrasound for pediatric interventions such as vascular access (in particular, central-line placement), lumbar puncture, fluid drainage (paracentesis, thoracentesis, pericardiocentesis), suprapubic aspiration, and soft tissue incision and drainage. Our review of this evidence reveals that point-of-care ultrasound has become a powerful tool for improving procedural success and patient safety. Pediatric patients and clinicians performing procedures stand to benefit greatly from point-of-care ultrasound, because seeing is believing.

Moving Beyond the Stethoscope: Diagnostic Point-of-Care Ultrasound in Pediatric Practice.

Diagnostic point-of-care ultrasound (POCUS) is a growing field across all disciplines of pediatric practice. Machine accessibility and portability will only continue to grow, thus increasing exposure to this technology for both providers and patients. Individuals seeking training in POCUS should first identify their scope of practice to determine appropriate applications within their clinical setting, a few of which are discussed within this article. Efforts to build standardized POCUS infrastructure within specialties and institutions are ongoing with the goal of improving patient care and outcomes.

[Point-of-care ultrasound: Is it time to include it in the paediatric specialist training program?] / Ecografía a pie de cama: ¿es el momento de incluirla en la formación del pediatra?

Point-of-care ultrasound (POCUS) has become an essential tool for clinical practice in recent years. It should be considered as an extension of the standard physical examination, which complements and enriches it without substituting it. POCUS enables the physician to answer specific clinical questions about the diagnosis, to understand better the pathophysiological context, to orientate the treatment, and to perform invasive procedures more safely. Despite its current use in many centres, and in most paediatric sub-specialties, there are currently no specific recommendations addressing educational aims in the different training areas, as well as methodology practice and the certification process in paediatrics. These ingredients are essential for POCUS implementation in daily practice, with a quality guarantee in terms of efficiency and safety. Several POCUS experts in different paediatric medicine environments performed a non-systematic review addressing the main paediatric POCUS applications in paediatrics. The lack of educational programs in POCUS in Spain is also discussed, and the experience in the United States of America in this topic is provided. Considering the current situation of POCUS in paediatrics, we strongly believe that it is urgent to establish evidence-based recommendations for POCUS training that should be the base to develop educational programs and to include POCUS in the paediatric residency training.