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Emergency Ultrasound

Pediatric Emergency Ultrasound Update: Point-of-care Pediatric Cardiac Ultrasound: Are Kids’ Hearts Just like Little Adults?

By Marina Shpilko, DO 

Assessment of cardiac function and intravascular volume is an important part of managing acutely ill pediatric patients in the emergency department.1 Of particular concern is the infant who presents with shock. It is difficult to distinguish between primary respiratory pathology versus congenital or acquired heart disease. Chest x-rays are not reliable to make that distinction.2 While the identification of particular congenital heart lesions is complex and beyond the scope of bedside echocardiography, we can identify certain features that will help guide our clinical management.

The ED provider may utilize their knowledge of adult bedside echo and apply it to the pediatric population. Point of care ultrasound is used to answer specific questions such as: Is there a pericardial effusion? Is the global LV function impaired? Is cardiac activity present?

How is pediatric echo similar to adult echo, and what aspects set them apart?

  1. General Guidelines when approaching the pediatric echo:
    1. “Standard views”: Parasternal Long axis, Parasternal Short axis, Apical 4 chamber, and subxiphoid are employed.3 The Apical 4 tends to be easier in the pediatric population due to ease of scanning through comparatively much more elastic ribs.
  2. Assessment of LV function is similar to adults:
    1. Estimation of LV ejection fraction via qualitative and/or quantitative means.4
    2. Qualitative assessment is made by analyzing the myocardial thickness during systole and the change in ventricular chamber diameter during systole in comparison to diastole.
    3. Quantitatively calculating EF: Ejection fraction calculation using M mode is the most widely used in pediatric patients, and is derived from the fractional shortening (FS) measurement. Measurements of the LV systolic (ESD) and diastolic diameter (EDD) right below the mitral valve leaflets in the parasternal long axis views are necessary to obtain the fractional shortening, which is calculated using the formula FS = EDD − ESD/EDD × 100.4
    4. Obtaining Stroke Volume and VTI measurements are same in children as adults.
  3. IVC and volume status:
    1. Clinical assessment and measurements of filling pressures (CVP) did not predict fluid responsiveness in children, as in adults. In contrast to adults, pulse pressure variation and stroke volume variation did not predict fluid responsiveness in children.4
    2. IVC has, therefore, been studied as a tool to analyze intravascular volume.
    3. Studies have shown that decreased intravascular volume resulted in measurable decreases in IVC diameters. Conversely, the diameter of the descending aorta remains relatively stable.
    4. Since the size of the IVC in pediatric patients varies with their ages and sizes, researchers have looked at the ratio of IVC to Aorta. When measured by bedside US, the smaller the IVC is with respect to aorta. The more volume down your patient.5 They had found an IVC/Ao cutoff of 0.8, to be 86% sensitive and 56% specific for dehydration.6
    5. Finding the IVC in short axis, and measuring the diameter anterior to posterior in the midepigastrium, is analogous to adults.7
    6. This, however, still needs further investigation with large prospective trials. Currently, experts advocate for serial exams to guide resuscitation, rather than relying on one exam at a single point in time.3 One also needs to be cautious with asthmatic patients who, because of auto peep and increased intrathoracic pressure, may have a dilated IVC independent of their volume status.
  4. Right Ventricle and Diastolic Function:
    1. The right ventricular wall thickness and size may be examined in multiple views, with the apical view being easiest.
    2. The RV size is qualitatively examined by visual estimation and compared to the LV size. Normal: “when the RV is smaller than the LV (approximately 60% of the LV size) and the RV apex is lower than the LV.”4 As with the assessment of LV, ventricular wall function and thickness should be estimated.4
    3. Keep in mind that the newborn heart is different in shape. It is more globular and the RV will be bigger in comparison (1 to 1 ratio). Tends to “normalize” by 1st month of life.
  5. Pericardial effusion:
    1. Similarly identified in pediatric echocardiography as in adults with evidence of anechoic fluid surrounding the pericardium.
    2. Tamponade physiology is similar to adults as well. Signs that support the diagnosis:
      1. collapse of the right atrium during ventricular systole
      2. IVC dilatation with no respiratory change.4
    3. Note - may need to review the images in a slower mode if tachycardia prevents estimation of diastolic function.
  6. Clues for congenital heart disease emergencies: targeted questions for starting point:
    1. How is the global cardiac function?
    2. Are there four chambers of the heart present?
    3. Is the septum intact?8
    4. Is the IVC and Aorta located where you would expect to find them?

References

  1. Longjohn M, Wan J, Joshi V, et al. Point-of-care echocardiography by pediatric emergency physicians.
    Pediatr Emerg Care. 2011;27(8):693-6.
  2. Molaie A, Abdinia B, Zakeri R, et al. Diagnostic value of chest radiography in pediatric cardiovascular diseases: A retrospective study in Tabriz, northwest of Iran. Intern J Pediatr. 2015;3(2.1);9-13.
  3. Marin JR, Abo AM, Arroyo AC, et al. Pediatric emergency medicine point-of-care ultrasound: summary of the evidence. Crit Ultrasound J. 2016:8(1):16
  4. Gaspar HA, Morhy SS. The role of focused echocardiography in pediatric intensive care: A critical appraisal. Biomed Res Int. 2015;2015.
  5. Chen L, Kim Y, Santucci KA. Use of ultrasound measurement of the inferior vena cava diameter as an objective tool in the assessment of children with clinical dehydration. Acad Emerg Med. 2007;14(10): 841-5.
  6. Chen L, Hsiao A, Langhan M, et al. Use of bedside ultrasound to assess degree of dehydration in children with gastroenteritis. Acad Emerg Med. 2010;17(10):1042–1047.
  7. Pershad J, Myers S, Plouman C, et al. Bedside limited echocardiography by the emergency physician is accurate during evaluation of the critically ill patient. Pediatrics. 2004;114: 667–671.
  8. Hellman, Anton. Emergency Medicine cases. “Congenital Heart Disease Emergencies”
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