**4. Cardiac**

The use of echocardiography has aided the evaluation of cardiac anatomy and function of the unborn fetus and the newborn. Ordering an assessment of the heart by ultrasound is a routine practice in the NICU. There has been a need to supplement the clinical assessment and current hemodynamic monitoring as they do not provide a comprehensive picture of cardiac output and organ perfusion states. The need for serial measurements is another unmet need with routine cardiac echocardiograms since transitional physiology after birth and during illness often require repeated measurements. Bedside POCUS for cardiac assessment is still an emerging practice as training to evaluate the heart is one of the hardest POCUS skills. Despite its difficulty there are probably more neonatologists worldwide with training to assess the heart through limited functional assessments than there are for non-cardiac POCUS. Cardiac POCUS is not intended to replace a cardiology assessment or structural echocardiogram. It is intended to be limited and dynamic assessment of hemodynamic of the heart to help with clinical decision making. Cardiac assessment in neonates is unique due to the dynamic changes that occur in the first few weeks of life making it challenging to order frequent dynamic assessments. The ability to help determine rapid determination of hemodynamics with serial functional assessments makes it increasingly attractive to work it into the daily workflow [5]. The focus of neonatal cardiac POCUS is to concentrate on a limited set of assessments that are helpful in determining the real-time hemodynamics. These include assessment of the patent ductus arteriosus (PDA), ventricular function, filling of the heart and volume assessment.

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**Figure 3.** PDA (a) large PDA, (b) no PDA, LPA-left pulmonary artery, DA-descending aorta.

To start, cardiac POCUS can provide a rapid qualitative assessment of contractility: normal, hyperactive, reduced contractility (mild, moderate, or severe). Fractional shortening measurements are relatively easy to obtain and provide quantitative information. Cardiac filling as a measure of volume assessment can also be determined quickly. The PDA represents an important shunt to assess to facilitate clinical management to determine if the PDA is contributing to cardiorespiratory compromise or systemic hypoperfusion. The PDA can be determined to be open or closed (**Figure 3**). The presence of a patent ductus arteriosus can lead to an overestimate of cardiac output using usual left ventricular output measurements. An alternative measure of cardiac output using superior vena caval flow (SVC) measurements as a surrogate measure has been proposed [6–9]. Unfortunately, SVC flow has not become widely used as it has proven to be difficult to minimize inter-operator variability in this measurement. While several examples of benefit of neonatal cardiac POCUS have been published, there remains a paucity of neonatal clinical studies to validate each of the functional assessments and their ability to improve diagnostic or management of the sick neonate [10, 11]. As more neonatologists become comfortable with the skillset of cardiac echocardiography, there is a need for improved standardization and quality assurance [12, 13]. There have been some attempt to standardize the practice but many feel that the standards set are excessive and restrict early adoption [14, 15]. The anatomic assessment of the heart for the most part should be left to the cardiologist but it is equally important to recognize patterns of normal structure to know when there is suspicion of a congenital heart lesion.

Nevertheless, despite a number of hurdles, there remains tremendous promise that neonatal cardiac POCUS can provide a focused assessment to provide hemodynamic information to the bedside clinician.

### **5. Lung**

Other areas of benefit from POCUS in the NICU are arterial line placement where localization of the vessel and flow identification by Doppler ultrasound can be performed. A modified Allen test with Doppler ultrasound evaluation of collateral flow is useful prior to the procedure. Real-time ultrasound can result in fewer attempts and less chance of a hematoma as

**Figure 2.** PICC localization (a) upper PICC, (b) lower PICC, PICC-peripherally, inserted central catheter, RA-right

The use of echocardiography has aided the evaluation of cardiac anatomy and function of the unborn fetus and the newborn. Ordering an assessment of the heart by ultrasound is a routine practice in the NICU. There has been a need to supplement the clinical assessment and current hemodynamic monitoring as they do not provide a comprehensive picture of cardiac output and organ perfusion states. The need for serial measurements is another unmet need with routine cardiac echocardiograms since transitional physiology after birth and during illness often require repeated measurements. Bedside POCUS for cardiac assessment is still an emerging practice as training to evaluate the heart is one of the hardest POCUS skills. Despite its difficulty there are probably more neonatologists worldwide with training to assess the heart through limited functional assessments than there are for non-cardiac POCUS. Cardiac POCUS is not intended to replace a cardiology assessment or structural echocardiogram. It is intended to be limited and dynamic assessment of hemodynamic of the heart to help with clinical decision making. Cardiac assessment in neonates is unique due to the dynamic changes that occur in the first few weeks of life making it challenging to order frequent dynamic assessments. The ability to help determine rapid determination of hemodynamics with serial functional assessments makes it increasingly attractive to work it into the daily workflow [5]. The focus of neonatal cardiac POCUS is to concentrate on a limited set of assessments that are helpful in determining the real-time hemodynamics. These include assessment of the patent ductus

arteriosus (PDA), ventricular function, filling of the heart and volume assessment.

compared with palpation.

66 Current Topics in Intensive Care Medicine

atrium, SVC-superior vena cava, IVC-inferior vena cava.

**4. Cardiac**

The evaluation of lung by POCUS in neonates is increasingly practiced as the imaging technique is relatively simple and the lung is readily accessible for interrogation through the chest wall. Several recent articles have noted lung ultrasound to be as good if not better than X-ray as a diagnostic modality. Reduction in cost of image acquisition and exposure to ionizing radiation improves quality of care as well as patient safety [16]. Neonatal lung POCUS is similar to pediatric lung POCUS except that the neonate has very thin soft tissue in the chest with thin ribs and a cartilaginous sternum that enables larger windows of viewing. From a technical perspective, we need a high frequency transducer like a 7–15 MHz hockey stick or equivalent linear array transducer. The detection of common respiratory conditions has been documented making it potentially possible to define the parenchymal lung disease by characteristic patterns to the common respiratory conditions such as pneumonia (PNA), transient tachypnea of the newborn (TTN) and respiratory distress syndrome (RDS). The ability to make an urgent diagnosis is where the greatest utility of lung POCUS may lie as acute respiratory compromise often requires rapid diagnostics. The presence of air or fluid such as blood, transudate or exudate in the pleural space is readily discernable by US.

studies have validated the ability to distinguish between RDS and transient tachypnea of the newborn (TTN) [20, 21]. In TTN ultrasound changes include abnormalities of pleural lines, absence of A-lines, and interstitial syndrome or pulmonary edema. Pneumonia has been described to have A-lines, interstitial syndrome and possible lung consolidation. Lung POCUS has been able to differentiate meconium aspiration syndrome from other respiratory conditions since it is also associated with absent A-lines, lung consolidation, and interstitial syndrome.

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The role of lung ultrasound may not replace chest radiographs but may offer more time sensitive information and reduce the total number of radiographs taken. The evaluation of lung by POCUS in neonates is increasingly being studied and practiced. The most promising application may be during resuscitation where early detection and management of conditions like

Neonatal intubation remains a difficult high level skill. Although there are much less intubations taking place compared to a decade ago, the need to establish a secure airway remains ever important. This is particularly true for resuscitation of neonates <28 weeks gestation. The current standard of practice to confirm the placement of the endotracheal tube (ETT) is with chest x-ray (CXR).The passage of the ETT into the trachea or esophagus can be discerned readily using a transverse probe position in adults and pediatric subjects [22–25]. POCUS can be used to rapidly and accurately visualize the anatomic position of the ETT position in preterm and term infants [26] (**Figure 5**). Unlike in pediatric or adult patients, evaluating the ETT in the newborn

**Figure 5.** Endotracheal tube placement ETT-endotracheal tube, RPA-right pulmonary artery.

pneumothoraces and pleural effusions are life-saving.

**6. Endotracheal tube**

The complication of spontaneous pneumothorax (PTX) at birth is one such condition that may be aided by lung POCUS. PTX will display several differing US patterns compared to normal lung. The characteristic findings on US of PTX in neonates are similar to adults and children (**Figure 4**). Normal lung appears homogeneous in texture with the occasional presence of hyperechoic linear A (horizontal) and B (vertical) lines. Movement of the parietal and visceral pleura against each other during respiration creates a "shimmering effect" or an "ants marching effect" which is termed lung sliding. The presence of the sliding lung sign rules out a pneumothorax on B mode [17]. Further confirmation of a PTX can be achieved with M mode which displays the data from a single line in an image mapped against time on the x-axis. The appearance of moving lung tissue results in a granular appearance similar to a sandy "seashore" with the "waves" at the top representing the static soft tissue above the lungs. Some data suggests that US may not be as sensitive for PTX in neonates [18].

The underlying changes in RDS involve loss of the smallest airspaces (alveoli or saccules). This generates denser tissue that gives the appearance of "white lung" using lung POCUS. Some have proposed a scoring system to categorize lung disease in RDS to assist in increasing specificity for diagnosing RDS [19]. This score can reliably predict the need for surfactant treatment in preterm babies less than 34 weeks gestation treated with nasal CPAP from birth. Several

**Figure 4.** Pneumothorax (a) normal lung, (b) pneumothorax.

studies have validated the ability to distinguish between RDS and transient tachypnea of the newborn (TTN) [20, 21]. In TTN ultrasound changes include abnormalities of pleural lines, absence of A-lines, and interstitial syndrome or pulmonary edema. Pneumonia has been described to have A-lines, interstitial syndrome and possible lung consolidation. Lung POCUS has been able to differentiate meconium aspiration syndrome from other respiratory conditions since it is also associated with absent A-lines, lung consolidation, and interstitial syndrome.

The role of lung ultrasound may not replace chest radiographs but may offer more time sensitive information and reduce the total number of radiographs taken. The evaluation of lung by POCUS in neonates is increasingly being studied and practiced. The most promising application may be during resuscitation where early detection and management of conditions like pneumothoraces and pleural effusions are life-saving.
