The role of Neonatologist Performed Echocardiography in the assessment and management of neonatal shock

Abstract

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.

Fig. 1

Identification of the stage of shock by simultaneous measurement of cardiac output and blood pressure

Fig. 2

Central blood flow measurements. Different assessments of central blood flow are shown, such as LVO, RVO, SVC flow, and Dao flow. It should be noted that central blood flow does not always represent systemic blood flow in the presence of shunts. CorBF coronary blood flow, DAo descending aortic flow, LtR left-to-right, LVO left ventricular output, PBF pulmonary blood flow, RVO right ventricular output, SBF systemic blood flow, SVC superior vena cava flow, VR venous return

Fig. 3

Assessment of left ventricular output (LVO). LV outflow tract diameter is measured from the parasternal long-axis view (a). The diameter measurement should be performed at the hinge points of the aortic valve at end-systole (b). The velocity time integral (VTI) in the LV outflow tract should be assessed in the apical five-chamber view or apical long-axis view using pulsed-wave Doppler with the sample volume just below the aortic valve (c). The pulsed wave Doppler recording is paused to obtain a smooth VTI envelope for exact tracing of the signal (d)

Fig. 4

Assessment of right ventricular output (RVO). RV outflow tract diameter is measured from the tilted parasternal long-axis view (a). The diameter measurement should be performed at the pulmonary valve insertion (b). The velocity–time integral (VTI) is acquired in the same view or in the parasternal short-axis view, depending on angle orientation (c). The pulsed wave Doppler recording is paused to obtain a smooth VTI envelope for exact tracing of the signal (d)

Fig. 5

Assessment of superior vena cava (SVC) flow. The SVC diameter is measured at the entrance to the right atrium from the modified parasternal long-axis view (a). Both minimum and maximum diameters are measured through the heart cycle. Three to five consecutive heart cycles are analyzed with the average regarded as the mean SVC diameter (b). The subcostal view is used to assess SVC flow velocity (c). It is advised to average VTI tracings from eight to ten heart cycles to minimize variations secondary to respiration. Negative blood flow velocities (A-wave and sometimes a late-systolic negative wave) should be subtracted for a reliable SVC flow estimation (d)

Fig. 6

Assessment of descending aorta (DAo) flow. The velocity–time integral (VTI) of DAo flow can be assessed both from a high parasternal or low subcostal sagittal view using pulse-wave Doppler with a minimum angle of insonation (a). In the presence of any retrograde diastolic aortic blood flow, the DAo flow should be corrected by deducting the retrograde VTI from the antegrade VTI. The diameter of the DAo is measured in the short axis parasternal axis view, as close as possible to the plane of the aortic valve (b)

Fig. 7

Algorithm for an individualized, pathophysiology-based approach towards a low cardiac output state in newborn infants. Please note that there may be an overlap between underlying pathophysiological mechanisms and that they are not necessarily mutually exclusive. ECMO extracorporeal membrane oxygenation, MAwP mean airway pressure, NSAID non-steroidal anti-inflammatory drug, PPHN persistent pulmonary hypertension of the newborn, PDA patent ductus arteriosus, PDE phosphodiesterase, PVR pulmonary vascular resistance, SIRS systemic inflammatory response syndrome, SVR systemic vascular resistance, TTTS twin-to-twin transfusion syndrome

Fig. 8

Potential choices of cardiovascular drugs based upon the preferred hemodynamic effect (cardiovascular drugs presented in a random, non-prioritized order)

Fig. 9

Presumed effects of commonly used cardiovascular drugs in neonatal intensive care. X-axis (effect on vascular tone): the more to the right, the more vasodilatory effects; the more to the left, the more vasoconstrictory effects. Y-axis (inotropic properties): the higher on the Y-axis, the more inotropic characteristics. The larger the size of the (semi-)circle, the more chronotropic effects. It should be noted that the effect on vascular tone depends on the used dosage that determines which adrenergic receptors are activated (e.g., dopamine and epinephrine). Based on refs. ^,