Assessing fluid responsiveness with ultrasound in the neonatal intensive care setting: the mini-fluid challenge.

The mini-fluid challenge (MFC) can guide individualised fluid therapy and prevent fluid overload and associated morbidity in adult intensive care patients. This ultrasound test is based on the Frank-Starling principles to assess dynamic fluid responsiveness, but limited MFC data exists for newborns. This brief report describes the feasibility of the MFC in 12 preterm infants with late onset sepsis and 5 newborns with other pathophysiology. Apical views were used to determine the changes in left ventricular stroke volume before and after a 3 ml/kg fluid bolus was given over 5 min. Four out of the 17 infants were fluid responsive, defined as a post-bolus increase in stroke volume of 15% or more.  Conclusion: The MFC was feasible and followed the physiological principles of stroke volume and extravascular lung water changes and 24% were fluid responsive. The MFC could enable future studies to examine whether adding fluid responsiveness to guide fluid therapy in newborns can reduce the risk of fluid overload. What is Known: • Fluid overload is associated with morbidity and mortality. • The mini-fluid challenge (MFC) provides a personalised approach to fluid therapy. What is New: • The MFC is feasible in newborns. • The MFC followed the physiological principles of stroke volume and extravascular lung water changes.

Mortality in the neonatal intensive care setting: Do benchmarks tell the whole story?

AIM: Australian neonatal mortality data are collected and shared within collaborative networks. Individual unit outcomes are benchmarked between units and presented in quarterly or yearly reports. Low mortality is commonly interpreted as optimal performance. However, current collected data do not differentiate between death due to severe illness and death following treatment limitation. This study aims to explore the physiological condition immediately before death, and the proportion of deaths attributed to treatment limitation. METHODS: This retrospective single centre study of 100 consecutive deaths classified the physiological condition 12 h prior to death as stable or unstable using a clinical illness score based upon pH, oxygen saturation index, medications and blood product use. Documented discussions regarding expected outcomes and goals of management were reviewed for agreed upon treatment limitations and analysed against physiological stability. RESULTS: Causes of death were sepsis (n = 24), congenital anomalies (n = 20), extreme prematurity (n = 19), hypoxic ischaemic encephalopathy (n = 18), intraventricular haemorrhage (n = 11) and other (n = 8). Forty-eight infants were physiologically stable at 12 h before death. In infants classified as physiologically stable, 90% of deaths were in a scenario where palliative care was discussed and intensive care treatment was ceased. These deaths accounted for 43% of total mortality in our unit. CONCLUSION: A large portion of mortality in our unit could be attributed to treatment limitations in physiologically stable infants with high risk of neurodevelopmental impairment. Our study emphasises the need to consider the physiological status around time of death for optimal benchmarking of mortality between neonatal units.

Which left atrial volume measurement should we use in the neonatal intensive care?

BACKGROUND: Increased left atrial volume (LAV) is a marker of cardiovascular risk. Echocardiography standards to assess LAV in adults and children are the biplane area-length method (AL) and method of disks (MOD). LAV in neonatology is usually derived as M-mode ratio between the LA and the Aorta (LAAo). The aim of this study is to determine feasibility and reliability of these methods in neonatal clinical practice. METHODS: Clinically indicated echocardiograms in neonatal intensive care patients were retrospectively analyzed. Feasibility was determined with an image quality score describing insonation angle, foreshortening and wall clarity. Reliability was determined with Bland-Altman and correlation coefficient analysis of intra- and inter-observer measurements. RESULTS: 104 infants ranging from 23 to 39 weeks gestation were included. The feasibility of LAAo, AL and MOD was comparable (median image score 4 out of 6 points). Linear regression between AL and MOD was excellent (R2 0.99). LAAo best-fit with MOD was reached with curve-linear regression (R2 0.28) whereby a LAAo of 1.60 correlated with 1.24 ml/kg, but with a wide 95 % CI. The correlation coefficient within and between observers for LAAo, biplane AL, biplane MOD and monoplane MOD was 0.93 (0.87-0.96), 0.98 (0.96-0.99), 0.98 (0.96-0.99), 0.99 (0.97-0.99) and 0.58 (0.11-0.81), 0.75 (0.44-0.89), 0.92 (0.88-0.98), 0.96 (0.88-0.98) respectively. CONCLUSION: All methods were equally feasible and reliable when repeated by the same observer, but LAAo reliability was poor when repeated by a different observer. Biplane MOD was the most reliable and thus recommended in neonatal practice. Monoplane MOD performed well and could be considered as alternative but might be less accurate.

Global longitudinal strain is an informative index of left ventricular performance in neonates receiving intensive care.

Echocardiographic assessment of left ventricular function is crucial in NICU. The study aimed to compare the accuracy and agreement of global longitudinal strain (GLS) with conventional measurements. Real-life echocardiograms of neonates receiving intensive care were retrospectively reviewed. Shortening fraction (SF), ejection fraction (EF) and S' measurements were retrieved from health records. GLS was calculated offline from stored images. The association with stroke volume indexed for body weight (iSV) was evaluated by regression analysis. The diagnostic ability to identify uncompensated shock was assessed by ROC curve analysis. Cohen's κ was run to assess agreement. 334 echocardiograms of 155 neonates were evaluated. Mean ± SD gestational age and birth weight were 34.5 ± 4.1 weeks and 2264 ± 914 g, respectively. SF, EF, S' and GLS were associated with iSV with R2 of 0.133, 0.332, 0.252 and 0.633, (all p < .001). Including all variables in a regression model, iSV prediction showed an adjusted R2 of 0.667, (p < .001). GLS explained 73% of the model variance. GLS showed a better ability to diagnose uncompensated shock (AUC 0.956) compared to EF, S' and SF (AUC 0.757, 0.737 and 0.606, respectively). GLS showed a moderate agreement with EF (κ = .500, p < .001) and a limited agreement with S' and SF (κ = .260, p < .001, κ = .242, p < .001). GLS was a more informative index of left ventricular performance, providing the rationale for a more extensive use of GLS at the cotside.

Assessing Intracardiac Vortices with High Frame-Rate Echocardiography-Derived Blood Speckle Imaging in Newborns.

The left ventricle (LV) has a unique pattern of hemodynamic filling. During diastole, a rotational body or ring of fluid known as a vortex is formed due to the chiral geometry of the heart. A vortex is reported to have a role in conserving the kinetic energy of blood flow entering into the LV. Recent studies have shown that LV vortices may have prognostic value in describing diastolic function at rest in neonatal, pediatric, and adult populations, and may help with earlier subclinical intervention. However, the visualization and characterization of the vortex remain minimally explored. A number of imaging modalities have been utilized for visualizing and describing intracardiac blood flow patterns and vortex rings. In this article, a technique known as blood speckle imaging (BSI) is of particular interest. BSI is derived from high-frame rate color Doppler echocardiography and provides several advantages over other modalities. Namely, BSI is an inexpensive and noninvasive bedside tool that does not rely on contrast agents or extensive mathematical assumptions. This work presents a detailed step-by-step application of the BSI methodology used in our laboratory. The clinical utility of BSI is still in its early stages, but has shown promise within the pediatric and neonatal populations for describing diastolic function in volume-overloaded hearts. A secondary aim of this study is thus to discuss recent and future clinical work with this imaging technology.