Lung Ultrasound Induction of Pulmonary Capillary Hemorrhage in Neonatal Swine

Technical Notes on Liver Elastography: A Guide for Use in Neonates in Intensive Care Units

Background/Objectives: Liver elastography is increasingly used in neonatal intensive care units (NICUs) as a non-invasive, radiation-free, reproducible technique for assessing liver stiffness. This technique demonstrates substantial advantages over conventional ultrasound in diagnosing diffuse liver diseases by providing quantitative measures of tissue elasticity. This article aims to describe the most critical milestones for performing liver elastography ultrasound point-of-care, a tool increasingly used to complement traditional ultrasound in the study of the liver in intensive care units where the population is very susceptible to manipulation. Methods: Techniques such as point-shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) have become key in evaluating conditions such as hypoxic-ischemic liver disease, cholestatic diseases, storage and metabolic disorders, or infectious liver conditions. However, despite its usefulness, performing elastography in neonates, particularly in those weighing less than 1000 g or in high-frequency oscillatory ventilation, presents notable challenges, including the extreme sensitivity of neonates to touch, noise, and temperature changes and the difficulty in obtaining accurate measurements due to limited hepatic depth. Results: Key factors for the success of sonoelastography in this population include minimizing contact time, adjusting mechanical and thermal indices to meet biosecurity guidelines, and ensuring patient comfort and stability during the procedure. Despite these challenges, elastography has proven helpful in routine clinical practice. Conclusions: The growing evidence on elastography has provided standardized reference values, further enhancing its clinical applicability in NICU settings.

Point-of-Care-Ultrasound in Pediatrics: A Review and Update

Point-of-Care-Ultrasound (POCUS) has encountered a tremendous expansion in patient care. POCUS has taken a central role during invasive procedures. POCUS has expanded to most subspecialties from adult to pediatric and neonatal health care. POCUS in pediatrics has also become part of specific critical situations such as myocardial function assessment during cardiac arrest, extracorporeal membrane oxygenation deployment and neurological evaluation. In this review we will go over the most important historical aspects of POCUS. We will also review important aspects of POCUS in the intensive care unit, cardiologist evaluation and in the emergency department among others.

Ultra-high frequency lung ultrasound in preterm neonates: a test validation study on interpretation agreement and reliability

OBJECTIVE

To verify if increasing frequency, through the use of ultra-high frequency transducers, has an impact on lung ultrasound pattern recognition.

DESIGN

Test validation study.

SETTING

Tertiary academic referral neonatal intensive care unit.

PATIENTS

Neonates admitted with respiratory distress signs.

INTERVENTIONS

Lung ultrasound performed with four micro-linear probes (10, 15, 20 and 22 MHz), in random order. Anonymised images (600 dpi) were randomly included in a pictorial database: physicians with different lung ultrasound experience (beginners (n=7), competents (n=6), experts (n=5)) blindly assessed it. Conformity and reliability of interpretation were analysed using intraclass correlation coefficient (ICC), area under the curve (AUC) of the multi-class ROC analysis, correlation and multivariate linear regressions (adjusting for frequency, expertise and their interaction).

OUTCOME MEASURES

A (0-3) score based on classical lung ultrasound semiology was given to each image as done in the clinical routine.

RESULTS

ICC (0.902 (95% CI: 0.862 to 0.936), p<0.001) and AUC (0.948, p<0.001) on the whole pictorial database (48 images acquired on 12 neonates), and irrespective of the frequency and physicians' expertise, were excellent. Physicians detected more B-lines with increasing frequency: there was a positive correlation between score and frequency (ρ=0.117, p=0.001); multivariate analysis confirmed the score to be higher using 22 MHz-probes (β=0.36 (0.02-0.7), p=0.041).

CONCLUSION

Overall conformity and reliability of interpretations of lung ultrasound patterns were excellent. There were differences in the identification of the B-patterns and severe B-patterns as increasing probe frequency is associated with higher score given to these patterns.

Frame Rate Exposimetry for Pulmonary Capillary Hemorrhage During Lung Ultrasound

OBJECTIVES

Lung ultrasound (LUS) is a powerful and accessible clinical tool for pulmonary diagnosis, but risk of pulmonary capillary hemorrhage (PCH) presents a safety issue. The dependence of PCH in a rat model of LUS was evaluated for image frames-per-second (fps) and associated on-screen Mechanical Index (MIOS ) and Thermal Index (TI).

METHODS

A Philips iE33 machine with L15-7io probe was used to scan anesthetized rats in a warmed water bath. B mode was applied at 9 MHz with settings of 34, 61 and 118 fps. After 2 minutes of exposure at an MIOS setting, samples were obtained for assessment of PCH areas on the lung surface. Ultrasound parameters were measured to determine the in situ MIIS at the lung surface.

RESULTS

The PCH trend counter-intuitively decreased with increasing fps, with areas of 19.5 mm2 for 34 fps (MIOS  = 1.0, TI = 0.8, 4080 images), 9.6 mm2 at 61 fps (MIOS  = 1.0, TI = 0.5, 7320 images) and 7.5 mm2 at 118 fps (MIOS  = 1.1, TI = 0.4, 14,160 images). The PCH was not significantly different for 34 fps (TI = 0.5, MIOS  = 0.8) (10.7 mm2 ), compared to 61 and 118 fps, above, indicating some value for the TI as a predictive indicator of PCH. MIIS thresholds were 0.42, 0.46, and 0.49 for 34, 61 and 118 fps, respectively.

CONCLUSIONS

The increase in PCH at low fps was associated with delivering more relatively high amplitude grazing pulse exposures during slower image scans. No significant PCH was found for the MIOS setting of 0.5, corresponding to in MIIS values of 0.35-0.39.

Lung Ultrasound Induction of Pulmonary Capillary Hemorrhage in Rats With Consideration of Exposimetric Relationships to Previous Similar Observations in Neonatal Swine

OBJECTIVE

Lung ultrasound (LUS) has become an essential clinical tool for pulmonary evaluation. LUS has been found to induce pulmonary capillary hemorrhage (PCH) in animal models, posing a safety issue. The induction of PCH was investigated in rats, and exposimetry parameters were compared with those of a previous neonatal swine study.

METHODS

Female rats were anesthetized and scanned in a warmed water bath with the 3Sc, C1-5 and L4-12t probes from a GE Venue R1 point-of-care ultrasound machine. Acoustic outputs (AOs) of sham, 10%, 25%, 50% or 100% were applied for 5-min exposures with the scan plane aligned with an intercostal space. Hydrophone measurements were used to estimate the in situ mechanical index (MIIS) at the lung surface. Lung samples were scored for PCH area, and PCH volumes were estimated.

RESULTS

At 100% AO, the PCH areas were 73 ± 19 mm2 for the 3.3 MHz 3Sc probe (4 cm lung depth), 49 ± 20 mm2 (3.5 cm lung depth) or 96 ± 14 mm2 (2 cm lung depth) for the 3.0 MHz C1-5 probe and 7.8 ± 2.9 mm2 for the 7 MHz L4-12t (1.2 cm lung depth). Estimated volumes ranged from 378 ± 97 mm3 for the C1-5 at 2 cm to 1.3 ± 1.5 mm3 for the L4-12t. MIIS thresholds for PCH were 0.62, 0.56 and 0.48 for the 3Sc, C1-5 and L4-12t, respectively.

CONCLUSION

Comparison between this study and previous similar research in neonatal swine revealed the importance of chest wall attenuation. Neonatal patients may be most susceptible to LUS PCH because of thin chest walls.