Introduction

Pneumonia is a leading cause of death in children around the world. The most common initial test for pneumonia is chest radiograph/x-ray (CXR) despite it having limited sensitivity and exposing children to radiation. Growing evidence shows that point-of-care ultrasound (PoCUS) can reliably detect lung consolidation with equal, if not better, sensitivity than CXR. Computed tomography (CT) provides the best test characteristics but is impractical and carries the cost of significant radiation.

Lung ultrasound (LUS) has excellent test characteristics, is noninvasive, delivers no ionizing radiation, and does not require a patient to be moved to a radiology department. For these reasons there is great potential for its use at the bedside in the diagnosis of pneumonia in children.

 

Why Ultrasound?

Given that air scatters ultrasound waves, it was traditionally thought that lung ultrasound would not be useful to detect pathology. However, over the last two decades there is a growing body of evidence supporting the use of ultrasound in various lung pathologies. Since lung pathology, such as pneumonia, leads to edema and fluid accumulation within the alveoli, areas of consolidation can be seen on ultrasound as long as this fluid reaches the pleural line. Fortunately, this is the case in most patients, particularly in children who have small lungs.

Several meta-analyses examining test characteristics of LUS for pediatric pneumonia have been published (1,2,3). The initial meta-analysis published in 2015 found a pooled sensitivity of 96% and specificity of 93% and an area under the ROC of 0.98 (3). All studies revealed LUS as equal if not superior to detecting consolidation compared to CXR (1,2,3). In the adult literature, a study comparing the test characteristics of LUS and CXR to the gold standard CT revealed a significantly better sensitivity of lung ultrasound: 86% vs 64%, with similar specificities. (4)

Jones et al. published a randomized-control trial examining the feasibility of replacing CXR with LUS for the diagnosis of pneumonia in children. They showed a 30-60% reduction in the use of CXR, depending on the level of experience of the ultrasonographer, as well as decreased ED length of stay. The inter-rater reliability for LUS in this practical study was 0.81, showing excellent agreement (5). A meta-analysis examining accuracy of LUS in novice vs advanced sonographers did find that novice sonographers had decreased accuracy, but the sensitivity and specificity remained 80% and 96% respectively, with an area under the ROC of 0.97 (6). Though, the question does remain as to what makes someone novice vs expert in LUS.

Additional questions about LUS remain to be answered. Specifically, what is the value of each abnormal finding on LUS and which findings are indicative of bacterial pneumonia necessitating antibiotic treatment? Studies agree that findings such as hepatization, air bronchograms and large subpleural consolidations are consistent with bacterial pneumonia, but focal B-lines, small subpleural consolidation and irregularities of the pleural lining can also be found in viral etiologies. A recent study looking at the significance of sub-centimeter, subpleural consolidations concluded that as an isolated finding, these are not indicative of bacterial pneumonia (7). Further study in this area continues to emerge. Jones et al. raised caution that LUS could unintentionally increase antibiotic usage rates if there is no clear definition of bacterial pneumonia (5).

 

Modality	Sensitivity	Specificity	Area under the ROC
LUS	95.5% (93.6 – 97.1)	95.3% (91.1 – 98.3%)	0.98
CXR	86.8% (83.3 – 90.0)	98.2% (95.7 – 99.6)

 

What am I looking at?

Subxiphoid View

FIGURE 5: Subxiphoid view labeled

The liver can be found in the near field, with the heart in the far field. In standard convention, the right side of the heart will be on the left and in the near field of your screen, with the left side of the heart or the right and in the far field of the screen. The ventricles are found in the near field, with the atria in far field.

The border of the right ventricle and the intra-ventricular septum form a “7” in this view.

 

FIGURE 6: Subxiphoid view illustrating the area of interest (pericardial space).

 

Parasternal Long View:

FIGURE 7: Parasternal long view labeled

This view allows you to see the long axis of the heart. You will see three main sections of the heart moving parallel across the screen. In the near field, you will see the right ventricle. The aortic valve and left ventricular outflow track are found on the left side of the screen in mid field. The third parallel section is the left atrium and mitral valve flowing into the left ventricle. The descending aorta is found in the far field.

Indications

• Chest pain
• Dyspnea
• Blunt & penetrating trauma
• Unexplained hemodynamic instability

 

Equipment

• Ultrasound machine
• Phased Array (Cardiac) or Curvilinear (Abdominal) probe
• Ultrasound gel

Note: The small footprint and low frequency of the phased array probe make it ideal to generate images of the heart through the intercostal windows.

 

Technique

Pericardial effusions can be identified in all cardiac views, but we will focus on two with the highest yield: the subxiphoid view (also used in FAST scans) and the parasternal long axis view. The other views (parasternal short view and apical four chamber view) have greater utility for other indications and will be reviewed in a separate module.

Getting Started:

• Place the ultrasound machine so it is easily viewed while scanning.
• Ensure the patient is in the supine position.
• Drape the patient to allow access to both the abdomen and anterior chest.
• Set the ultrasound machine to an abdominal or cardiac setting, with the screen indicator on the left.
• You may use either the curvilinear or phased array probe.

Figure 1: Phased array and curvilinear probes with screen indicator position highlighted.

Subxiphoid View

1. Place the probe inferior to the xiphoid process.
2. Ensure the probe marker is directed towards the patient’s right shoulder.
3. The probe will typically be angled about 15 degrees upward from the surface of the abdomen.
   • Place your hand on top of the probe to facilitate the shallow angle of this view.
4. Aim the probe towards the patient’s left shoulder.
5. Use the liver as your acoustic window (the liver will be seen in the near field).
6. Identify the heart, including the posterior border of the heart, RV, septum and LV.
   • These structures should make the shape of a ‘7’ on the screen.
7. Sweep SLOWLY through the heart from anterior to posterior.
   • Identify any anechoic fluid collection in the pericardium.

 

FIGURE 2: Probe position subxiphoid view

 

Troubleshooting Steps

• Ask patient to bend their knees to release tension on abdominal wall.
• Continue to advance the probe superiorly until you reach the xyphoid process.
• Use generous amounts of gel to minimize needing to “dig” under the xyphoid process.
• Ask the patient to “take a deep breath and hold it” to bring the heart closer to the probe.
• The image will improve as the probe moves closer to the heart.

 

Parasternal Long View

1. Identify the 3-4^th intercostal space along the left sternal border.
2. Direct the probe marker towards the patient’s right shoulder.
3. Ensure the probe is directly perpendicular to the patient’s chest wall.
4. Identify the following:
   • Near field: right ventricle
   • Middle field: left ventricular outflow tract, left atrium, mitral valve, left ventricle
   • Far field: descending aorta
5. Assess for an anechoic fluid collection in the pericardium, deep to the myocardium of the LA and LV.

FIGURE 3: Probe position parasternal long view

 

Troubleshooting Steps: Lung Shadow

• Ask the patient to breathe out completely and hold – helps to remove the lung shadow.
• Rolling the patient into the left lateral decubitus position can also bring the heart closer to the chest wall and decrease the lung shadow.

 

Note: By convention, cardiology performs echocardiograms with the probe indicator on the right of the screen. Emergency physicians perform POCUS with the probe marker to the left of the screen. To maintain consistency with other uses of POCUS in the emergency department, the views described in this module are obtained with the probe marker on the left of the screen.  In the parasternal long axis this results in a mirror image compared to the traditional cardiology parasternal long view.

 

FIGURE 4: Parasternal long view. Emergency Medicine convention versus Cardiology convention

Introduction

The ability to use point of care ultrasound to detect pericardial effusions is an important skill for the acute care practitioner. In the trauma setting, the ability to rapidly identify a pericardial effusion as the cause of hemodynamic instability can focus early interventions and guide disposition decisions. Alternatively, in patients with non-traumatic chest pain or dyspnea, the ability to identify the presence or absence of a pericardial effusion can help to narrow the differential diagnosis.

POCUS allows physicians to make a rapid diagnosis of pericardial effusion in real time.

 

Why Ultrasound?

Currently, any urgent complete echocardiogram is done by cardiology. This can present logistical challenges; particularly after hours. POCUS is a simple and efficient way to identify a pericardial effusion, no matter the cause. It allows physicians to screen patients who would otherwise only be examined with poorly sensitive tools such as auscultation and chest radiography.

From a resource utilization perspective, this allows formal echocardiograms to be reserved for those with more complex medical needs, including congenital cardiac disease or high-risk clinical presentations. Ultrasound is low cost, portable and free of ionizing radiation. It is the diagnostic modality of choice for cardiac imaging given its ability to provide a real time look at the heart and its function [1]. Further, POCUS exams are easily repeatable and serial evaluation may be used as the patient’s status changes. This is an important consideration as the rate at which fluid may accumulate in the pericardium can vary [2]

Cardiac POCUS has been in use for many years in the emergency department. In 1988, Mayron et al found that 80% of emergency physicians felt comfortable diagnosing a pericardial effusion after only four hours of training [3]. Famously, a retrospective analysis of patients presenting to the emergency department with penetrating cardiac trauma had shown that the use of POCUS to identify pericardial effusion was associated with improved survival and time to diagnosis. In the study by Plummer et al., of 49 patients with pericardial effusions with equal predicted survival rates (according to TRISS methodology), 100% of those who had beside ultrasound survived, compared to only 57% of those who did not get bedside ultrasound [4]. In this study, it was felt that a main contributor to survival was the improved time to diagnosis. Specifically, POCUS allowed for time to diagnosis of 15.5 ± 11.4 minutes, whereas those without POCUS had an average time to diagnosis of 42.4 ± 21.7 minutes (p < 0.001) [4]. Further, many studies have looked at the sensitivity and specificity of emergency physicians in diagnosing pericardial effusions. These studies show a range of sensitivity from 83-100%, specificity of 98-99% and overall accuracy of 97.5-99% when compared to cardiologist readings [2,5,6]. Point of care ultrasound performs similarly in the hands of pediatric providers, with a sensitivity of 100% and a specificity of 99.5% for the detection of pericardial effusion in a pediatric emergency population [7].

• Sensitivity Range 83-100%
• Specificity Range 98-99%
• Accuracy Range 97.5-99%

Emergency Physician POCUS for Detection of Pericardial Effusion

References

1. Dychter SS, Gold DA, Carson D, Haller M. Intravenous therapy. J Infus Nurs 2012; 35:84–91.
2. Lee SU, Jung JY, et.al. Factors associated with difficult intravenous access in the pediatric emergency department. J Vasc Access. 2020; 21(2):180-185
3. Yen K, Riegert A and Gorelick MH. Derivation of the DIVA Score: A clinical prediction rule for the identification of children with difficult venous access. Pediatric Emergency Care. 24(3):143-147.
4. Riker MW et.al. Validation and refinement of the DIVA Score: A clinical prediction rule for identifying children with difficult intravenous access. Academic Emergency Medicine. 2011; 18:1129-1134.
5. Schnadower et al. A Pilot Study of Ultrasound Analysis before Pediatric Peripheral Vein Cannulation Attempt. Academic Emergency Medicine. 2007, 14(5). p483–485
6. Stolz LA, Stolz U, Howe C, Farrell IJ, and Adhikari S. Ultrasound-guided peripheral venous access: a meta-analysis and systematic review. J Vasc Access. 2015; 16(4): 321-326
7. Heinrichs et al. Ultrasonographically Guided Peripheral Intravenous Cannulation of Children and Adults: A Systematic Review and Meta-analysis. Annals of Emergency Medicine. 2013; 61:4.
8. Bauman, Braude and Crandall. Ultrasound-guidance vs. standard technique in difficult vascular access patients by ED technicians. AJEM. 2009; 27.
9. Stolz et al. Prospective evaluation of the learning curve for ultrasound-guided peripheral intravenous catheter placement. J Vasc Access 2016; 17(4): 366-370.
10. Maiocco and Coole. Use of Ultrasound Guidance for Peripheral Intravenous Placement in Difficult-to-Access Patients. J Nurs Care Qual 2010; 27(1): 51-55.
11. Vinograd, AM, et.al. Ultrasonographic guidance to improve first-attempt success in children with predicted difficult intravenous access in the emergency department: A randomized controlled trial. Annals of Emergency Medicine. 2019; 74(1):19-27
12. Gottlieb, Sundaram, Holiday and Nakitende. Ultrasound-Guided Peripheral Intravenous Line Placement: A Narrative Review of Evidence-based Best Practices. WJEM 2017; 18(6): 1047-54.
13. Fields et al. The effect of vessel depth, diameter, and location on ultrasound-guided peripheral intravenous catheter longevity. AJEM 2012; 30(7): 1134-1140.
14. Gottlieb, Holladay and Peksa. Comparison of Short- vs Long-axis Technique for Ultrasound-guided Peripheral Line Placement: A Systematic Review and Meta-analysis. Cureus 2018; 10(5): e2718. DOI 10.7759/cureus.2718.
15. Takenshita J, et.al. Superiority of dynamic needle tip positioning for ultrasound-guided peripheral venous catheterization in patients younger than under 2 years old: A randomized controlled trial. Pediatric Critical Care. 2019; 20(9) e410-e414.]

Summary

Difficult IV access is a common issue faced in the pediatric patients and ultrasound guidance improves success and efficiency over the traditional land marking approaches. A dynamic approach is preferred, and the choice of out-of-plane vs in-plane technique is operator dependent. The ideal vessel for USG PIV placement is greater than 0.4cm in diameter, between 0.3 and 1.5cm in depth and at least 1cm in length. Long catheters are preferred to increase longevity.

 

Remember:

1. Prepare: Gather your equipment
2. Optimize: Position, tourniquet, warm compress, and local anesthetic
3. Identify: Select a target vessel. Confirm it is venous looking at wall thickness and compressibility
4. Poke: Introduce the needle and follow the tip through its course from the skin into the vessel
5. Confirm: Confirm catheter placement and secure it to the patient

Pitfalls:

Immediate: unsuccessful attempts are most commonly due to puncturing the posterior wall and failing to visualize the needle tip as it enters the vessel. If care is not taken accidental injury to surrounding structures or inadvertent arterial cannulation is possible.

Late: Dislodgement is the most common cause of USG PIV failure as is often due to the placement of a short catheter in a deeper vein. It is recommended that A MINIMUM of 1 cm of catheter is left within the vessel after placement to prevent dislodgement by movement of the skin and soft tissues and ideally at least half of the catheter length is intraluminal. Given deeper vessels are often targeted in the US-guided technique compared to the landmark technique it is often beneficial to choose a longer catheter for placement.

Performing USG PIV Access

1. Preparation
2. 1. Patient: position the patient in a comfortable position that allows the operator access to the area of interest. Don’t forget that commitment to comfort strategies can aid your IV placement whether using a landmark or US-guided approach. Remember to:
      1. Make a plan
      2. Apply numbing cream
      3. Use comfort positions
      4. Breastfeed or use sucrose
      5. Use distraction
      6. Use positive language
      7. Consider using procedural sedation as per local policy
   2. Ultrasound: Place the US machine in a place where both the US screen and patient’s vein can be seen simultaneously.
   3. Set the depth and gain for the anatomy being visualized. Use a vascular preset if available on your ultrasound machine. Ensure both the probe marker and dot on the screen are on the operator’s left.

 

2. Localize target vessel by ultrasound
3. 1. Prior to preparing the sterile field, apply a tourniquet and look for preferred sites: consider scanning both arms and saphenous until you find the best site.

TIP: To focus on ideal targets, set the machine depth to its minimum setting.

1. 2. Using anatomy to guide probe placement identify a site for USG cannulation: the preferred sites include the larger vessels of the forearm, saphenous and in cases of difficult access the distal upper arm.
   3. Remember ideal vessel characteristics include a 0.3-1.5 cm depth, 4 mm diameter (often difficult to ensure in smaller patients) and a straight segment of least 1cm in length.

 

3. Confirm identification of vein and surrounding structures
4. 1. Confirm the visualized structure is a vein using compression, lack of pulsatility and if doubt remains absence of pulsatile flow on color doppler to differentiate it from any surrounding structures. Remember if the tourniquet is up a vein may not show any flow, but an artery should have pulsatile flow.
   2. Identify any nearby structures to be avoided including arteries, nerves and tendons.
   3. Consider using a marker to mark the skin to approximate the path of the vessel and planned approach.

 

4. Preparing for the procedure
5. 1. Once the site is selected, wipe off any excess gel from the patient and transducer.
   2. Prepare the machine by cleaning the probe, cord and machine. Obtain sterile US gel and apply a thin strip to the US probe followed by a sterile sheath or adhesive dressing. Take care not to contaminate the sterile dressing during application.
   3. Ensure you have the proper catheter dependent on vessel size and depth, tourniquet, IV tubing, saline flushes, tape or dressing to secure the IV and additional people to aid with patient holding, traction on the vein and passing of supplies.

 

 

5. Introduce the needle
   1. Out-of-plane technique:

1. 1. 1. Orient the probe so the vein is in the center of the screen, be sure the hand holding the probe is braced on the patient either with the palm or outstretched finger to minimize probe movement. Additionally, wrapping the US cord around the arm can eliminate any “pull” on the probe to decrease movement and slippage.
      2. Note the depth of the vessel and choose an appropriate angle of approach (45 degrees for deep structures, 30 degrees for more superficial structures)
      3. With the needle perpendicular to the center of the probe, advance the needle into the skin aiming for the vein visualized at the center of the probe.
      4. Once the needle and catheter have pierced the skin pause to find the hyperechoic needle tip on the ultrasound screen by fanning the US probe towards the needle. If having difficulty, try gently “jiggling” the needle to identify surrounding tissue movement. Once visualized move the probe slightly forward and continue to advance the needle tip towards the vein until it comes into view. Continue this process, following the tip of the needle by moving the US probe and then the needle until the needle tip enters the vessel lumen. This creeping technique ensures that the needle tip is visualized and helps prevent posterior wall puncture.
      5. As the needle enters the vein the vessel wall will indent or “tent”, at this point advance in small amounts until the vessel wall recoils and the hyperechoic tip of the needle is confirmed in the center of the vessel.
      6. Flatten the angle and advance the needle a little further in the vessel before advancing the catheter.
      7. Confirm the needle tip has not pierced the posterior wall of the vessel by moving the US past the end of the visualized needle prior to advancing the catheter over the needle and securing the IV.

 

Video 3: Out-of-plane technique (creep technique)

 

 

1. 2. In-plane technique:

1. 1. 1. Once the vessel is identified in the transverse orientation, rotate the probe 90 degrees while keeping the vessel centered on the screen until the entire length of the vessel is visualized on the screen. Brace the probe hand firmly on the patient so the probe does not move as even small movements can result in losing alignment. Additionally, wrapping the US cord around the arm can eliminate any “pull” on the probe to decrease movement and slippage.
      2. Note the depth of the vessel and choose an appropriate angle of approach.
      3. With the needle parallel to the probe enter the skin adjacent to the end of the probe and advance the needle along the plane of the US beam.
      4. Follow the entire length of the needle as it passes through tissues and advances into the target vessel. If the full length of the needle/needle tip is lost from view DO NOT MOVE THE PROBE as you will lose sight of the vessel, simply withdraw the needle towards the skin, adjust your angle and reattempt.
      5. Once the needle tip is visualized within the vessel lumen, flatten the angle and advance the needle a little further within the vessel lumen.
      6. Ensure you are visualizing the tip of the needle within the vessel lumen by imaging the length of the needle before advancing the catheter and securing the IV.

 

Video 4: In-plane technique

 

6. Confirm catheter placement
7. 1. Visualize the full length of the catheter in the vessel.
   2. Confirm with observation of saline turbulent flow within the vessel with flush.

 

7. After thoroughly cleaning the US gel from the skin secure the catheter. Finally remove sterile cover from the US probe and clean the machine and document the procedure in the chart as per local policy.

Technique

 

Techniques for USG PIV placement vary and can be adapted to best suit the user.

Techniques include:

1. Static vs dynamic
2. Single vs dual operator
3. In-plane vs out-of-plane

 

Static vs Dynamic

In the static approach US is used solely to identify vessels and the overlying is marked. In a dynamic approach the US is used to guide the placement of the catheter into the vessel from skin puncture to cannulation. The static approach has significant limitations in terms of success due to movement of skin and subcutaneous tissues in relation to the underlying vessels. The dynamic use of US to guide needle placement is the preferred method in PIV access but can be more technically challenging to learn.

 

Single vs Dual Operator

USG PIV access can be performed with either single or dual operators – one person performs the ultrasound while the other performs the procedure. This provides the advantage of freeing up the proceduralist’s hands for IV placement alone. This technique also does not require the dual hand eye coordination of directing the ultrasound transducer as well as performing the procedure.

The dual operator technique is particularly useful in the situation where the operators have different skills sets, such as a nurse with good cannulation skills but limited US experience or a doctor who is comfortable identifying veins on US but lacks confidence in advancing and securing catheters. In such cases a dual operator approach may be preferred. Yet, with two operators, coordinating the ultrasound image relative to the needle can be technically challenging, so there is no preferred approach.

 

Out-of-plane vs in-plane

Finally, ultrasound guided procedures can be performed with either an out-of-plane or in-plane technique. Each has it advantages and drawbacks. The out-of-plane approach (figure 9) is generally preferred by novice users and has similar success rates compared to the in-plane approach, but special care must be taken to visualize the needle tip and avoid posterior wall puncture [14]. In pediatric patients a dynamic out-of-plane approach has been found to be successful and may be easier for novices [8,15].

 

Figure 9: Out-of-plane technique

 

The in-plane technique (figure 10) allows for visualization of the needle along its entire path and can reduce the risk of puncture of the posterior vessel wall, but it is a technically more challenging approach as keeping the vessel and needle in plane is difficult and the technique can be limited by vessel characteristics, operator experience, and patient movement.

 

Figure 10: In-plane technique

Equipment

 

Ultrasound equipment:

• High frequency linear probe
• Sterile probe cover (sterile adhesive dressing or full cover)
• Sterile US gel

 

IV Equipment (figure 8)

• Topical anesthetic agent (may need to be applied after vessel selection)
• IV Catheter (long PIV or mid-length catheter preferred)
• Tourniquet (consider use of double tourniquet with proximal and distal placement)
• Disinfectant for skin preparation (i.e. alcohol swab)
• IV tubing/saline flush
• Material to secure PIV in place (tape, arm board, etc)

 

Figure 8: Equipment for US-guided PIV access