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Review
Point-of-care ultrasound for the pediatric regional anesthesiologist and pain specialist: a technique review
  1. Michelle S Kars1,
  2. Andrea Gomez Morad2,
  3. Stephen C Haskins3,
  4. Jan Boublik4 and
  5. Karen Boretsky5
  1. 1 Department of Anesthesiology, Steven and Alexandra Cohen Children’s Medical Center, New Hyde Park, New York, USA
  2. 2 Department of Anesthesiology Critical Care and Pain Medicine, Boston Children’s Hospital, Boston, Massachusetts, USA
  3. 3 Department of Anesthesiology, Hospital for Special Surgery, New York, New York, USA
  4. 4 Department of Anesthesiology, Stanford Hospital and Clinics, Stanford, California, USA
  5. 5 Department of Anesthesiology, Critical Care and Pain Medicine, Harvard Medical School, Boston, Massachusetts, USA
  1. Correspondence to Dr Michelle S Kars, Anesthesiology, Steven and Alexandra Cohen Children's Medical Center, New Hyde Park, New York, USA; mkars{at}northwell.edu

Abstract

Point-of-care ultrasound (PoCUS) has been well described for adult perioperative patients; however, the literature on children remains limited. Regional anesthesiologists have gained interest in expanding their clinical repertoire of PoCUS from regional anesthesia to increasing numbers of applications. This manuscript reviews and highlights emerging PoCUS applications that may improve the quality and safety of pediatric care.

In infants and children, lung and airway PoCUS can be used to identify esophageal intubation, size airway devices such as endotracheal tubes, and rule in or out a pulmonary etiology for clinical decompensation. Gastric ultrasound can be used to stratify aspiration risk when nil-per-os compliance and gastric emptying are uncertain. Cardiac PoCUS imaging is useful to triage causes of undifferentiated hypotension or tachycardia and to determine reversible causes of cardiac arrest. Cardiac PoCUS can assess for pericardial effusion, gross ventricular systolic function, cardiac volume and filling, and gross valvular pathology. When PoCUS is used, a more rapid institution of problem-specific therapy with improved patient outcomes is demonstrated in the pediatric emergency medicine and critical care literature.

Overall, PoCUS saves time, expedites the differential diagnosis, and helps direct therapy when used in infants and children. PoCUS is low risk and should be readily accessible to pediatric anesthesiologists in the operating room.

  • pediatrics
  • critical care
  • emergency care

https://doi.org/10.1136/rapm-2020-101341

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    Introduction

    Point-of-care ultrasound (PoCUS) is a focused ultrasound examination performed at the bedside by appropriately trained clinicians to obtain diagnostic information, often in critical scenarios, to guide decision making.1 PoCUS is a well-established tool for bedside evaluation in adult patient populations in emergency medicine,2 critical care,3 and perioperative period.4–6 PoCUS provides high-quality physiological information relevant to many organ systems (cardiac, pulmonary, and gastrointestinal) allowing for more comprehensive and informed decision making.7–9 The incorporation of PoCUS into everyday clinical care for pediatric practitioners, unfortunately lags behind the adult practice and publications on pediatric perioperative PoCUS are limited.2–4 10 Likely, PoCUS implementation into pediatric anesthesia practice will advance once the benefits are realized in a manner similar to the adoption of ultrasound guidance for regional anesthesia in children following the documentation of advantages in adult patients.4 ,4 11–14 Similar to its use in adult regional anesthesia and pain medicine, PoCUS can be used to guide the management of pediatric patients in a variety of settings, including assessment of gastric contents prior to regional blockade as well as to guide the management of a patient who is hemodynamically unstable or in respiratory distress following a regional block or pain procedure.11–13 PoCUS is becoming an essential diagnostic tool and the care of pediatric patients will improve as these skills are increasingly implemented.

    Although there are many similarities between PoCUS imaging for pediatric and adult populations, the indications and interpretation are different because surgical procedures, comorbidities, and physiological responses of infants and children differ significantly. For example, respiratory etiologies account for a higher percentage of intraoperative cardiac arrests in children compared with adults, and PoCUS has proven value in distinguishing cardiac from respiratory etiologies in the presence of hemodynamic instability. Infants are also a high-risk group for intraoperative cardiac arrest from a variety of causes including a six times higher incidence of local anesthetic systemic toxicity.15 Pyloromyotomy is a pediatric surgical procedure with potential safety advantages conveyed by gastric ultrasound.16 PoCUS for perioperative pediatric patients is, therefore, distinct from adult practice in many ways.

    This article will provide an overview of the current research on the topic to include indications, acquisition, interpretation, and integration of findings into decision making in the pediatric perioperative setting. Although there are various applications, this article will highlight airway and lung, gastric, and cardiac imaging. Of note, consent was obtained for all images of children published in this article. The ultimate goal is to demystify PoCUS in the pediatric population and provide evidence of advantageous uses to facilitate increased utilization of PoCUS for the pediatric regional anesthesia and pain medicine practitioner.

    Ultrasound for airway and lung

    Airway and lung ultrasound is a useful tool to rule out pneumothorax or phrenic nerve paralysis associated with regional anesthesia and to differentiate the etiology of respiratory distress. This is especially relevant in children where the overwhelming majority of surgical patients (97%) having regional anesthesia also receive general anesthesia with assisted or controlled ventilation.15 Ultrasound imaging offers new ways to identify proper endotracheal tube (ETT) size and position and varying causes of respiratory distress.

    Airway

    Indications

    Ultrasound imaging can be used to determine ETT location and proper size. Appropriate sizing of the ETT is important in children to avoid excessive tracheal pressure while optimizing resistance to breathing and to minimize the number of attempts at intubation. Traditionally, formulas based on weight, height, and age have a predictive accuracy of only 31%–45% for both cuffed and uncuffed ETT.17 18 In addition, a child’s proportionally large head, small mouth opening, bigger tongue, anterior larynx, and short epiglottis make the visualization of the glottis difficult with pediatric tracheal intubations resulting in more intubation attempts and misplaced ETT. Prolonged or multiple intubation attempts result in faster arterial desaturation given the high metabolic rate and high oxygen consumption of growing children. Inadvertent esophageal intubation during attempted endotracheal intubation occurs in up to 21% of infants with resultant hypotension and the initiation of chest compressions in 4% and 3% of these patients, respectively.19 This makes the placement of ETT in infants and small children a high-risk procedure with good outcomes dependent on the rapid verification of ETT position. The rapid verification of proper ETT position is traditionally confirmed by auscultation and end-tidal capnography, both of which can be unreliable.

    Acquisition

    For tracheal ultrasound, the patient is placed in a supine position with the chin tipped upwards for intubation. A high-frequency linear transducer placed transversely over the trachea directly above the sternal notch images both the trachea and the esophagus (figure 1). The esophagus is lateral to the trachea. The transducer may need to be temporarily removed to allow the chin to dip down for the introduction of the laryngoscope.

    Figure 1
    Figure 1

    Image showing correct transducer placement and resultant ultrasound image: (A) trachea, (B) esophagus.

    Interpretation and integration

    Measurement of the diameter of the subglottic trachea using ultrasound correlates with airway caliber and can be used to calculate appropriate ETT outer diameter with a predictive accuracy of 60%–75%.17 18 The presence of air in the trachea impedes the transmission of ultrasound waves making it difficult to directly view the ETT in the airway. Therefore, alternative information is used to indicate the ETT location.20 During the intubation, an observation of an empty esophagus and widening subglottis indicates successful tracheal intubation, whereas the appearance of the ETT in the esophagus, “double trachea sign,” indicates esophageal intubation20–22 (figure 2). Adult and pediatric literature show sensitivity and specificity of 98.5%–100% and 75%–100%, respectively, for this method .21 23 24 This determination of successful intubation is quickly accomplished in real time and eliminates test ventilations. Limitations in visibility may occur with obesity, abnormal airways, short necks, and cervical collars.

    Figure 2
    Figure 2

    Ultrasound image showing endotracheal tube in the esophagus. (A) Trachea (unchanged), (B) Esophagus dilated to the size of trachea giving the appearance of side-by-side tracheas.

    Lung

    Lung ventilation can be confirmed with an ultrasound visualization of the pleural movement. Although the alveoli and lung parenchyma cannot be directly visualized due to the presence of and impedance by the air, characteristic artifact patterns can be used to identify normal lung and pathological lung conditions.

    Indications

    Children have an increased risk of endobronchial intubation due to relatively short tracheal length. Unrecognized bronchial intubation accounts for 4% of cardiac arrests from respiratory etiology in the closed claims study of anesthetized children.25 Auscultation is currently the gold standard for confirmation but fails to identify as many as 38% of endobronchial intubations in adult elective intubations and 5% of pediatric intubations.26 27

    Acquisition

    In children, the transducer is selected based on patient size, the ultrasound approach, and the depth of the target for interrogation. For superficial imaging of the pleura, a high-frequency (6–18 MHz) linear transducer is preferred; for patients over 40 kg, phased array and convex transducers can also be used. The transducer is placed vertically (indicator towards the head) over an intercostal space at the midclavicular line or in the midaxillary line (figure 3) and moved in the vertical plane to view at least two rib shadows.

    Figure 3
    Figure 3

    Midaxillary transducer with the sagittal orientation for the interrogation of the pleural movement.

    Normal findings:

    1. Lung sliding (pleural movement) is viewed between the ribs. During respiration, lung expansion causes the parietal and visceral pleuras (which appear as one structure) to slide against each other creating a shimmering appearance referred to as “lung sliding.”

    2. Lung pulse refers to the movement of the visceral pleura along the parietal pleura concurrent with each cardiac contraction. Pulsations of the heart are transmitted to the lung parenchyma resulting in small changes in lung volume creating pleural movement evidencing intact pleura.

    3. A-lines are horizontal artifacts produced from the air in the lung or chest cavity. Air reflectance of ultrasound waves prevents the visibility of structures below the pleura when air is present. Some of the reflected ultrasound waves will, however, bounce back and forth between the chest wall structures (muscle, fascia, and pleura) and the transducer generating reverberation artifact referred to as A-lines. These horizontal lines appear below the pleura with the same spacing as structures found above the pleura. They are present in both normal lungs and pneumothorax (figure 4).

    4. B-lines are created when air is replaced in the alveoli by fluid, septal thickening, or other interstitial lung disease. B-lines originate at the pleural line and are long, vertical hyperechoic lines that continue the entire depth of the image (figure 5). They obscure A-lines and move with pleural movement. Up to two B-lines per rib space are considered normal especially in dependent areas of the lung.

    Figure 4
    Figure 4

    A-lines, horizontal artifacts produced from the air in the lung or chest cavity.

    Figure 5
    Figure 5

    B-lines: characteristic of a pulmonary interstitial disease.

    Interpretation and integration

    The absence of lung sliding occurs during the absence of ventilation such as endobronchial intubation of the contralateral side, ipsilateral bronchial obstruction (foreign body, clot, and mucous), or esophageal intubation. Lung sliding will also be absent in conditions in which the pleuras are not directly opposed, (pneumothorax and pleural effusion) or when the pleuras are adhered due to scarring, inflammation, and masses.

    As most endobronchial intubations are right sided, an initial observation of lung sliding on the right confirms that the ETT is in the trachea and not the esophagus. The subsequent appearance of lung sliding on the left is the confirmation of bilateral lung ventilation. Lung pulse in the absence of lung sliding is highly suggestive of the endobronchial intubation of the contralateral lung, ipsilateral bronchial obstruction (foreign body, clot, and mucous), or esophageal intubation.

    Ultrasound imaging correctly identified endobronchial intubation in 95%–100% of adults and children compared with 62% using auscultation.24 26 A 12% increase in accuracy of detecting endobronchial intubation can be realized with the use of lung sliding in children.27 A lack of pleural sliding can, however, also indicate bronchial obstruction or pneumothorax. A single pediatric study reports that an ultrasound visualization of a saline-inflated ETT cuff (saline is an excellent conductor of sound waves) has a sensitivity and specificity of 99% and 96%, respectively, of identifying the correct ETT depth.28

    Thoracic ultrasound can be used to assess for pulmonary pathology and has been studied in the pediatric emergency department and intensive care unit (ICU) populations. Detailed reviews of adult and pediatric techniques and characteristic images are available.9 11 29 The presence of three or more B-lines per rib space is a non-specific finding and indicates interstitial disease such as atelectasis, pulmonary edema, pneumonia, or acute respiratory distress syndrome. Thoracic ultrasound imaging of the dependent lung fields can detect anesthesia-induced atelectasis with an 88% sensitivity and 87% specificity in mechanically ventilated infants undergoing laparoscopy.30 The resolution of atelectasis following recruitment interventions such as the addition of positive end-expiratory pressure (PEEP) can be monitored in real time.30 31 Thoracic ultrasound imaging is currently the first-line study for the diagnosis of pneumonia in children presenting to the emergency department.32–34

    The utility of ultrasound in detecting a pneumothorax is well documented.35 When the pneumothorax is directly beneath the transducer, the normal lung sliding during respiration and cardiac lung pulse are absent. B-lines, characteristic of lung consolidation, are not present while A-lines are preserved. In children, pneumothorax can occur during central line placement, brachial plexus blocks, and a variety of surgeries. A common procedure in toddlers is bronchoscopy for a tracheobronchial foreign body where pneumothorax and hypoxia are not uncommon. Pneumothorax can be rapidly ruled out with an ultrasound examination and other sources of the hypoxia are more quickly considered.

    In summary, bedside ultrasound imaging of the airway and chest has many emerging applications in children to assist in endotracheal intubation and to detect causes of respiratory distress. Increased incorporation into anesthesia practice has the potential to positively impact patient care.

    Ultrasound for the evaluation of gastric content

    Bedside point-of-care gastric ultrasound imaging provides information to potentially assess aspiration risk before general anesthesia or sedation in children. Aspiration of gastric content is an infrequent but a serious complication of anesthesia with an incidence of 0.04%–0.1% in pediatric patients.36–39 PoCUS gastric imaging is a non-invasive, bedside student to potentially identify children at increased risk for pulmonary aspiration of gastric contents.40

    Indications

    Routine preoperative pediatric gastric ultrasound is not a current standard of care but rather a means to stratify or clarify risk in targeted populations.40 High-risk children include those with uncertain nil-per-os (NPO) status, trauma, and those children with comorbidities known to delay gastric emptying. Children may not understand the importance of remaining NPO and may violate NPO guidelines when not directly observed. The pediatric literature reports a rate of non-compliance with NPO guidelines as high as 13%and 7% of children who report compliance have either solid content (1.7%) or clear fluid >1.5 mL/kg (4.5%)41 confirmed with ultrasound imaging. Comorbidities that delay gastric emptying include bowel obstruction, pyloric stenosis, acute abdomen, neuromuscular disorders, diabetes, trauma, opioid administration, severe liver dysfunction, and renal failure. 36 Descriptions in the literature about the application of gastric ultrasound in children are sparse.16 42 43 In small infants undergoing pyloromyotomy, a qualitative ultrasound assessment of the antrum can be used to judge the adequacy of gastric suctioning and to subsequently guide the anesthesia induction technique.16 In a single study, gastric suctioning of infants produced an antral area consistent with an empty stomach in 30 of 34 infants who received an inhalation induction, whereas 4 infants had a rapid sequence induction (RSI) due to excessive residual fluid. When gastric ultrasound was used in children to evaluate the gastric volume and evidence of gastric blood after ear, nose, and throat surgery (tonsillectomy, adenoidectomy, dental extraction, cleft palate repairs, maxillary or mandibular surgery, and endonasal surgery), the mean gastric volume did not change significantly before and after the procedures.42 A report of two children with uncertain gastric emptying used ultrasound imaging to identify “full stomachs” with subsequent modification of the anesthetic.43

    Acquisition

    The imaging for children is very similar to the technique reported in adult patients.40 44–46 Ultrasound transducer is placed in the epigastric region to obtain a sagittal view of the abdomen. The patient could be positioned supine or right lateral decubitus (RLD) with the head elevated 30–45 degrees; a lateral position has more sensitivity to detect gastric content than a supine position due to the movement of the content to dependent areas (figure 6). Early studies in pediatrics analyzed the correlation between ultrasound measurement and gastric content determined by MRI before and after the ingestion of know quantities of fluid with the best correlation found in children imaged in the RLD position.47 Children over 40 kg can be scanned with a low-frequency curvilinear transducer, whereas smaller children (less than 40 kg) and infants can be imaged with a linear high-frequency transducer.12 46

    Figure 6
    Figure 6

    The head elevated 30–45 degrees; the ultrasound transducer is placed in the epigastric region to obtain a sagittal view of the abdomen.

    Interpretation and integration

    An empty antrum (figure 7) is flat and oval shape, described as a “bulls-eye” appearance, whereas a full stomach has an antrum distended by contents that have characteristic appearances of fluids (hypoechoic; figure 8), a mixture of solids in liquid (hyperechoic mobile particles in a hypoechoic medium) and fluid with air (homogeneous hyperechoicity with an appearance of frosted glass; figure 9). A qualitative assessment of the stomach as “empty” or “non-empty”48 using a three-point antral grading system is validated in children. Patients are classified according to the character and volume of gastric contents using antral grades 0–2. Grade 0 is an empty antrum in both supine and RLD. A grade 0 antrum correlates with negligible gastric volume. A grade 1 antrum is defined as clear fluid (anechoic content) seen in the RLD only, but not in the supine position. Both grade 0 and grade 1 antrums are common in fasting children (>95% of cases) and correlate with low volumes of gastric fluid consistent with normal baseline secretions (<1.5 mL/kg). Antral grade 2 is defined as visible clear fluid in both supine and RLD positions. A grade 2 antrum is uncommon in fasting children (<5% of cases) and correlates with a gastric volume >1.5 mL/kg. When a grade 2 antrum is identified or any amount of solid (heterogeneous/particulate) or thick fluid content (hyperechoic) is observed, there is a concern for increased risk of aspiration.

    Figure 7
    Figure 7

    An empty gastric antrum is observed located deeper to the left pole of the liver, and superficial to the splenic vein (SV) and the inferior vena cava (IVC).

    Figure 8
    Figure 8

    (A) The ultrasound image of fluid-filled antrum in a 3-year-old infant in the supine position with the head elevated 30 degrees. It has an appearance of hypoechoic contents inside a distended antral cavity. (B) Same patient in the right lateral decubitus. A, antrum; Ao, aorta; IVC, inferior vena cava; L, liver, SMA, superior mesenteric artery.

    Figure 9
    Figure 9

    The ultrasound image of solid filled antrum in an 11-year-old child. The distended antrum with loss of the posterior wall and content inside the cavity with mixed echogenicity.

    In pediatric patients, the amount of volume considered significant for increased aspiration risk is controversial but a volume greater than 1.5 mL/kg is generally considered concerning. A predictive gastric volume (mL) by age was developed by Spencer et al. Evaluating patients undergoing upper endoscopy, they found good agreement between gastric antral cross-sectional area (CSA) measurements and aspirated gastric volume suctioned via upper endoscopy in both supine and RLD positions, with a slight advantage for the RLD position. They also described two independent variables predicting gastric volume: age and antral CSA. CSA volume = (−7.8)+(3.5)(RLD CSA)+0.127 (age months).49

    The ultrasound visualization of any solid content in the antrum or a gastric fluid volume of >1.25 mL/kg in children scheduled for elective surgery was defined by Bouvet et al as “at-risk stomach.” With a median fasting duration time for solids of 13 hours and fluids of 4 hours, they found that none of the patients had solid content in the antrum, ix children (6%) had fluid in RLD and supine positions and two children had a gastric volume of >1.5 mL/kg. With this study, they calculated that the preoperative “at-risk stomach” in the pediatric population for elective surgery is about 1%.44

    Limitations apply to gastric imaging and its interpretation in children. Gastric ultrasound imaging is ideally performed preinduction and requires patient cooperation, which is often lacking in children. However, preoperative ultrasound assessment is feasible in >95% of children aged 1–16 years.44

    Any clinical decisions regarding induction technique, time of NPO status, or the use of aspiration prophylaxis have to be individualized according to the patient’s clinical condition. Gastric ultrasound does not negate NPO guidelines and emergency surgery should not be delayed for gastric imaging and an RSI performed as indicated.

    In conclusion, bedside gastric ultrasound imaging in pediatric patients is a feasible, simple, harm-free, and increasingly available technique that can clarify some aspects of aspiration risk in certain clinical scenarios and potentially help guide decision making. Additional literature is needed to assess clinical applications in pediatric patients. Current evidence suggests that similar to adults, it is a reliable tool to assess the nature and volume of gastric content.

    Focused cardiac ultrasound

    Transthoracic PoCUS of the heart, also known as focused cardiac ultrasound (FoCUS), is rapidly becoming an important monitor in anesthetized children. It is used in hemodynamically unstable children to narrow a differential diagnosis and direct care.10 50 Although the indications and standardized examination in children are similar in many ways to adult FoCUS, differences exist. FoCUS in pediatric patients is a hemodynamic monitor and not a replacement for comprehensive echocardiography by a pediatric cardiologist. The FoCUS examination is a limited, ultrasound examination of the heart that provides basic yes or no answers to questions specific to a clinical scenario.51–54 The basic FoCUS examination provides a visual assessment of the heart with the qualitative evaluation of the size of the cardiac chambers, thickness of the walls, ventricular function, intracardiac volume status, and the presence of pericardial effusion or air emboli.52 53 55 56

    Indications

    The most common indications for FoCUS in children are to diagnose etiologies for undifferentiated hypotension and tachycardia and to determine reversible causes of cardiac arrest.52 FoCUS can shorten the time to make a definitive diagnosis and institute appropriate therapy in pediatric emergency departments and ICU57–59 and improve outcomes.58 Serial FoCUS examinations can be used to monitor an intervention and confirm the resolution of pathology in real time.57 60 61 Given the higher likelihood of congenital heart disease (CHD) in children, it is important to understand that FoCUS is not to be used to diagnose structural abnormalities. The interpretation of echocardiography in children with structural CHD is very difficult and FoCUS in children with CHD is limited to the identification of acute conditions, such as pericardial effusion or air embolus, and to assess overall myocardial function.10 50 52

    Acquisiton

    Phased array transducers are used in FoCUS and have a small footprint and oscillate at low frequencies to allow the visualization of deep structures through the small windows between ribs. A linear phased array transducer oscillating at 1–5 MHz with a 2–3 cm square footprint produces satisfactory image quality in children of all sizes including small infants eliminating the need for an extensive number of transducers.10 A single go-to transducer eliminates the time and distraction of choosing, locating, and changing transducers. When a phased array transducer is not available, a convex transducer with a small footprint provides good-quality images in infants and smaller children for the subcostal four-chamber (S4CH) and parasternal short-axis (PSAX) views.10

    The standard windows and views are the same as those described in FoCUS for adult patients and adult and pediatric overviews are published.10 55 The S4CH view and the PSAX view are technically easier for novices to learn and are ideal for assessing left ventricle size and systolic function, movement of the intraventricular septum, and to evaluate for the presence of pericardial effusion (figure 10). The PSAX window is generally the most accessible in children who are positioned and draped for surgery. Although valvular pathology is less common in children compared with adults, the parasternal long axis gives the best view for gross valvular assessment. The S4CH view is the recommended imaging window during cardiopulmonaryresuscitation (CPR)62–64 because it is the least disruptive of chest compressions (figure 11). Suboptimal image acquisition can give misleading information and, when possible, several views should be obtained to confirm the interpretation.

    Figure 10
    Figure 10

    Images illustrating proper transducer placement and resultant normal images for the parasternal short-axis and subcostal four-chamber views of the heart. LV, left ventricle; RV, right ventricle.

    Figure 11
    Figure 11

    S4CH in a 6 kg infant showing images obtained using a linear phased array transducer (A) and curvilinear sequential transducer (B). The arrow indicates the direction of the index marker. (Reprinted with permission from Boretsky et al).10 LV, left ventricle; RA, right atrial; RV, right ventricle; S4CH, subcostal four-chamber view.

    Image acquisition in children can be both easier and more difficult compared with adults. The heart is located closer to the transducer resulting in less attenuation of the ultrasound signal and better overall image quality and, in the operating room, FoCUS is mostly performed on immobile anesthetized children. Challenges arise from smaller target structures, faster heart rates, probe to patient size mismatch, limited access to small patients under surgical drapes, and potentially uncooperative awake patients.

    Quantitative calculations are uncommon in pediatric FoCUS and qualitative assessment is more essential. Pediatric studies of FoCUS have demonstrated a good correlation between visually estimated (qualitative) and formally measured (quantitative) cardiac ejection fraction.65–67 Performing calculations during FoCUS for emergent events adds time to image acquisition and prolongs an examination for which rapid evaluation is a major strength.

    Interpretation and clinical integration

    Interpretation must always consider patient history and related pathologies. Only small series of perioperative applications of FoCUS appear in the literature.10 50 68 One series reported that 60% of the children receiving a new diagnosis or a change in therapy as the result of a FoCUS examination were American Society of Anesthesiology class 1 and 2.10 Compared with adults, otherwise healthy children, especially infants and smaller children, have a higher incidence of local anesthetic systemic toxicity, hemodynamically significant air emboli, and respiratory insufficiency induced cardiac arrest.10 15 69 Adverse intraoperative respiratory events are common in children with up to 40% of intraoperative cardiac arrests resulting from a primary respiratory etiology.69 FoCUS can differentiate a primary respiratory problem and a respiratory problem masquerading as a cardiac problem.70 71 There have been four case reports of hemodynamically significant air emboli diagnosed (two published and two unpublished)68 72 with three occurring in infants and one in an adolescent in the beach chair position. Local anesthetic systemic toxicity in infants occurs at a rate six times higher than in older patients although a case assessed and managed with FoCUS has not yet been reported in the literature.15

    FoCUS can determine cardiac activity in the presence or absence of a pulse.73 This provides critical information in children where pulse palpation is unreliable even when performed by experienced healthcare providers.74 75 Reversible causes of cardiac arrest including pericardial tamponade, hypovolemia, and pulmonary and air embolus can all be confirmed with FoCUS.22 62–64 72 76

    A rapid transition to extracorporeal membrane oxygenation (ECMO) for failed CPR, E-CPR, is especially useful in children with ventricular asystole.77 There is evidence that E-CPR for pediatric patients with in-hospital arrest requiring >10 min of standard CPR is associated with improved survival and neurological outcomes. There is also evidence that prolonged conventional CPR with ongoing use of epinephrine every 3–5 min (as recommended by pediatric advanced life support (PALS) protocol) and resultant elevated systemic vascular resistance may limit ECMO pump flows when implementing E-CPR.78 A more rapid determination of myocardial standstill using cardiac ultrasound may, thus, facilitate more rapid progression to E-CPR with improvement in outcomes. The time allowed for an ultrasound examination during CPR is strictly limited to the 10 s pause performed every 2 min per PALS protocol.

    In conclusion, FoCUS has become an important diagnostic tool in the setting of undifferentiated hypotension and tachycardia and cardiac arrest in children. FoCUS allows the real-time visualization of the heart and acts as a hemodynamic monitor to direct patient care. Evidence suggests that FoCUS facilitates more rapid diagnosis and quicker implementation of targeted therapy with the potential to improve patient outcomes.

    Summary

    Overall, the skills needed for all PoCUS applications include knowledge of indications, image acquisition, and interpretation of the images and the ability to incorporate the information into the clinical scenario. Although skills in image acquisition can mostly be transferred from adult precedent, the clinical scenarios and applications in children differ. As with all new technologies, there is a steep learning curve to the acquisition of PoCUS skills and the inconsistent implementation of PoCUS at various facilities caring for children can limit the use of this important emerging technology. PoCUS imaging can, however, facilitate diagnoses and more quickly direct targeted therapy with the potential to positively impact the perioperative care of children. Increased availability and implementation should be encouraged based on current evidence.

    Acknowledgments

    The authors acknowledge Ban Tsui, MD, MSc, FRCPC, Professor, Stanford University School of Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, for his expert advice in constructing the final manuscript.

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    Footnotes

    • Twitter @mkarsmd, @shaskinsMD, @janboublik MDPhD

    • Contributors MSK and KB designed and implemented the project. MSK, AGM, SCH, JB and KB wrote the manuscript. MSK and KB formatted and edited the manuscript. All authors were involved in revisions for submission.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement Data sharing not applicable as no datasets generated and/or analysed for this study. Data sharing not applicable.