Concise Critical Appraisal: Cardiac Ultrasound in Pediatric Septic Shock Assessment

In pediatrics, point-of-care ultrasound (POCUS) is increasingly being used in the evaluation of bronchiolitis, diaphragm function, and intracranial hypertension, among other conditions, leading one author to suggest that “essentially any structure that can be interrogated transcutaneously through a thin layer of gel may be assessed with POCUS in children.”¹ In 2020, the Emergency Care Research Institute (ECRI), a medical safety advisory council, published a list of safety concerns surrounding POCUS, which was subsequently endorsed by the Joint Commission. The list includes the absence of:

• Safeguards with training
• Well-defined pediatric critical care applications
• Appropriate program oversight
• Existing guidelines consistent with other specialties using ultrasound

 
Numerous adult and pediatric critical care physicians have argued that ECRI’s concerns are not based on current research.^1-3 In addition, American and European consensus guidelines for the use of targeted, serial hemodynamic POCUS examinations (not in the diagnosis of congenital heart disease, which is reserved for trained pediatric cardiologists) in neonates and critically ill children have been published.^4,5 Similar to the use of pulmonary artery catheters, though, it is not clear whether serial targeted hemodynamic POCUS improves outcomes in critically ill children. The assessment of focused cardiac ultrasound (FCU) by Arnoldi et al serves as a helpful start to answering this question.⁶
 
In this retrospective observational study, the authors sought to determine how clinical information gleaned from FCU could be used to augment clinical assessments in children with suspected septic shock. The study’s primary aim was to document how often a clinician’s hemodynamic characterization of a child with septic shock is altered by FCU, with 20% being the hypothesized value. The study’s secondary aim was to validate an expert-developed algorithm using FCU and pre-FCU clinical characterization for hemodynamic assessment and integration in treatment. By examining the concordance between the post-FCU clinician hemodynamic characterization and management with the results of the algorithm as well as determining patient outcomes when misalignment between the algorithm and clinician management occurred, the authors sought to determine whether using FCU in a standardized way could ultimately lead to improved outcomes.
 
For the purposes of this study, pre-FCU hemodynamic characterizations by clinicians included fluid-responsiveness, myocardial dysfunction, obstructive physiology and/or reduced systemic vascular resistance (SVR). FCU measurements included 1) inferior vena cava (IVC) respiratory variation, 2) IVC-to-descending-aorta anterior-posterior diameter ratio, 3) qualitative left ventricular (LV) and right ventricular (RV) contractility, 4) presence of RV dilation, 5) interventricular septal position, and 6) the amount of any pericardial effusion. The IVC measurements were used to determine fluid responsiveness; the amount of pericardial fluid, RV dilation, and septal position were used to diagnose an obstructive physiology; and the contractility measurements were used to determine myocardial dysfunction.
 
For the primary aim, the authors used data from 46 children and found that post-FCU hemodynamic characterizations differed from pre-FCU assessments 67% of the time (31/46). The most common newly identified physiology in the post-FCU assessments was myocardial dysfunction (32% [7/22]). Obstructive physiology and fluid responsiveness were the most commonly ruled out physiologies (63% [5/8] and 50% [13/26], respectively). The algorithm based on FCU data and pre-FCU clinical assessment demonstrated substantial concordance overall (33/48, k=0.66). For myocardial dysfunction and obstructive physiologies, concordance was near-perfect (k=1.00 and k=0.87, respectively). Fluid responsiveness demonstrated substantial concordance (k=0.62), and diminished SVR showed fair concordance (k=0.34). Of the 15 patients whose hemodynamic characterizations were misaligned, 5 were impossible to match because the algorithm excluded low SVR states if they were accompanied by another physiology. Finally, although the patients with misaligned hemodynamic characterizations demonstrated a trend toward persistent organ dysfunction at day 7 and a more complicated course than the patients with aligned hemodynamics, these differences were not statistically significant.
 
Ginsburg et al and Sanfilippo et al also examined the role of diastolic dysfunction in pediatric sepsis.^7,8 The study by Arnoldi et al demonstrates that FCU findings can be a helpful adjunct in the management of children with septic shock. However, to ensure safety, a larger prospective study should be designed to examine morbidity and mortality using algorithms consistent with those from other specialties.

References

1. Su E, Soni NJ, Blaivas M, et al. Regulating critical care ultrasound, it is all in the interpretation. Pediatr Crit Care Med. 2021 Apr 1;22(4):e253-e258. https://doi.org/10.1097/PCC.0000000000002600
2. Conlon TW, Kantor DB, Hirshberg EL, et al. A call to action for the pediatric critical care community. Pediatr Crit Care Med. 2021 Mar 3. Online ahead of print. https://doi.org/10.1097/PCC.0000000000002691
3. Su, E, Flores S, Ofori-Amanfo G. Finding a path to better sepsis outcomes in critical care ultrasound, one step at a time. Pediatr Crit Care Med. 2021 Mar 1;22(3):329-332. https://doi.org/10.1097/PCC.0000000000002671
4. Mertens L, Seri I, Marek J, et al; Writing Group of the American Society of Echocardiography; European Association of Echocardiography; Association for European Pediatric Cardiologists. Targeted neonatal echocardiography in the neonatal intensive care unit: practice guidelines and recommendations for training. Writing Group of the American Society of Echocardiography (ASE) in collaboration with the European Association of Echocardiography (EAE) and the Association for European Pediatric Cardiologists (AEPC). J Am Soc Echocardiogr. 2011 Oct;24(10):1057-1078. https://pubmed.ncbi.nlm.nih.gov/21933743/
5. Singh Y, Villaescusa JU, da Cruz EM, et al. Recommendations for hemodynamic monitoring for critically ill children-expert consensus statement issued by the cardiovascular dynamics section of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC). Crit Care. 2020 Oct;24(1):620. https://pubmed.ncbi.nlm.nih.gov/33092621/
6. Arnoldi S, Glau CL, Walker SB, et al. Integrating focused cardiac ultrasound into pediatric septic shock assessment. Pediatr Crit Care Med. 2021 Mar 1;22(3):262-274. https://doi.org/10.1097/PCC.0000000000002658
7. Ginsburg S, Conlon T, Himebauch A, et al. Left ventricular diastolic dysfunction in pediatric sepsis: outcomes in a single-center retrospective cohort study. Pediatr Crit Care Med. 2021 Mar 1;22(3):275-285. https://doi.org/10.1097/PCC.0000000000002668
8. Sanfilippo F, La Rosa V, Grasso C, et al. Echocardiographic parameters and mortality in pediatric sepsis: a systematic review and meta-analysis. Pediatr Crit Care Med. 2021 Mar 1;22(3):251-261. https://doi.org/10.1097/PCC.0000000000002622