Ultrasound case of the month - Placement comes first

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As any successful resident at the House of God knew: “placement comes first.” In procedures, confirmation of placement is also essential. Ultrasound use continues to expand across the clinical realm, proving to be more and more useful at the bedside. Read on to learn about ultrasound based confirmation of endotracheal tubes and central venous catheters!

Endotracheal tube placement confirmation

There are numerous challenges facing the emergency medicine workforce during the COVID-19 pandemic. One of the highest risk procedures for these patients is endotracheal intubation given the risk for aerosolization of viral particles. General guidelines recommend verifying proper endotracheal tube (ETT) placement by quantitative waveform end-tidal capnography (EtCO2) and a portable chest x-ray (CXR)1. However, this poses a problem in the current environment due to the increased need for, and scarcity of, personal protective equipment (PPE). Further, the process exposes additional healthcare staff (radiology technicians) and requires extensive decontamination of the portable x-ray machine. Both of these problems could be mitigated by utilizing ultrasonogrophy to confirm ETT placement in conjunction with EtCO2. Multiple studies have validated ultrasound (US) as a useful tool to confirm ETT placement in the emergency department with sensitivity and specificity in the high 90s1-4.

ETT placement can be confirmed utilizing direct and indirect US. Direct US visualizes the trachea during/after intubation while indirect US confirms tube location by idetnfiying secondary signs, such as bilateral lung sliding and diaphragmatic excursion.

How to confirm ETT placement using direct US:

  1. Using the high-frequency linear probe, place the probe in a transverse (marker toward patient’s right) position just cephalad to the suprasternal notch (Figure 1)5.
  2. The trachea should appear as a hyperechoic semilunar structure near the top of the screen filled with air (Figure 2). The endotracheal tube placed in the trachea is often described as a “bullet sign” with increased reverberation artifact (Figure 3)6.
  3. Intubation of the esophagus will produce a “double track” sign with two distinct lumens with reverberation artifact (Figure 4).
Figure 1. Linear probe positioning to assess for eTT placement.

Figure 1. Linear probe positioning to assess for eTT placement.

Figure 2. Axial section through the neck cephalad to the sternal notch, demonstrating empty trachea and esophagus.

Figure 2. Axial section through the neck cephalad to the sternal notch, demonstrating empty trachea and esophagus.

Figure 3. Still image of eTT in the lumen of the trachea, demonstrating the bullet sign.

Figure 3. Still image of eTT in the lumen of the trachea, demonstrating the bullet sign.

Figure 4. Double track sign consistent with Esophageal intubation. the trachea is visible on the left portion of the screen (T), and the esophagus containing ETT (E) on the right.

Figure 4. Double track sign consistent with Esophageal intubation. the trachea is visible on the left portion of the screen (T), and the esophagus containing ETT (E) on the right.

How to confirm ETT location using indirect US:

  1. After ETT placement, place the high-frequency linear probe in the longitudinal plane on bilateral superior rib spaces to assess for pleural lung sliding. Unilateral lung sliding indicates main-stem intubation, contralateral to the side of sliding (Figure 5).
  2. Obtain the right and left upper quadrant views with visualization of the diaphragm, using the curvilinear or phased array probe. Excursion of bilateral hemidiaphragms during inspiration confirms proper depth of ETT (Figure 5).

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Figure 5. Indirect ultrasound confirmation of ett placement. Capture of diaphragmatic excursion in the Right upper quadrant, suggesting successful expansion of the right Lung (Left). Normal pleural sliding, indicating expansion of the underlying lung (Right).

While a sonographic approach definitely has its benefits, there are some potential drawbacks. If an US machine is not already in the patient’s room or readily available, a portable CXR may be preferable due to its ability to provide more information. The need for multiple operators may limit dynamic asssessment. In addition to the intubator, an additional provider would be required to visualize the trachea during intubation in real time. Alternatively, in a single provider setting, a static technique can be employed. After intubation the provider can use US to visualize the trachea and confirm successful placement, and use indirect methods to assess for main stem intubation. This approach, in conjunction with auscultation and EtCO2, can mitigate the need for obtaining a CXR, thereby reducing the potential for additional exposure of healthcare personnel to aerosolized COVID-19. While ultrasound cannot determine the exact distance from the carina, the amount of information it provides is sufficient to proceed with mechanical ventilation and defer CXR until additional indications arise (ex: after obtaining central venous access, NG placement, clinical changes, etc.).

Central venous catheter placement confirmation

Central venous cather (CVC) placement is an essential procedure for emergency physicians. Placement in the internal jugular (IJ) or subclavian veins has known complications, namely malposition and pneumothorax (PTX). Due to these complications there has been a dogmatic practice of post procedural CXR to confirm placement and rule out PTX. Previous literature has cast doubt on the need for this practice, especially when utilizing the right IJ, but it remains standard of care7. Some clinicians advocate that US is able to effectively rule out malposition of the CVC as well as pneumothorax8-10. An US based post-CVC placement exam can decrease utilization of CXR, thus minimizing radiation, and shorten the time to confirmation and potential administration of multiple drugs through those ports.

Malposition

Ideally, the CVC should be placed into a large bore central vein in the thorax. Deep placement (i.e. into the right ventricle) can increase the risk of damage to the tricuspid valve or endocardium. If the catheter is in a smaller caliber or non-thoracic vein it can lead to sclerosis, occlusion or perforation of the vein, though occult perforation due to prolonged vessel irritation has been shown to be more of a theoretical concern11. Two steps are required to ensure the CVC is adequately placed in a large central vein. First, the IJ should be evaluated bilaterally to ensure the CVC is not traversing up the contralateral vein. Second, a saline flush can be rapidly infused through any port of the line while observing the right atrium on a parasternal long or subcostal view of the heart (Figure 6). If turbulent flow is immediately seen (less than 2 seconds) then it can be inferred the CVC is in a large central thoracic vein.

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Figure 6. US assessment of CVC placement. (Left to right) Assessment of Internal jugular (IJ) vein, above carotid artery, for CVC placement. Confirmation of wire placement in the IJ in a static transverse image. Rapid infusion of saline followed by turbulent flow seen in the right atrium and ventricle from a subcostal view.

Pneumothorax

Ruling out PTX is an US skill widely utilized in the e-FAST exam. In an experienced operator's hand, this exam can be completed quickly and is both sensitive and specific for PTX. Obtaining one view bilaterally of the lungs is 93% sensitive for PTX12. To brush up on thoracic ultrasound and PTX, please peruse the dedicated Taming the SRU post on thoracic ultrasound.

The Data

Figure 7. Potential protocol for uS-based CVC placement confirmation.

Figure 7. Potential protocol for uS-based CVC placement confirmation.

Data surrounding the use of US to assess CVC placement continue to accumulate in the emergency medicine and critical care literature. A recent emergency medicine based study utilized a saline flush to cause turbulent flow in the right atrium as confirmation of appropriate placement. This method showed a sensitivity of 86.6% and a specificity of 100% for correct CVC placement13. A meta-analysis of critical care and emergency medicine studies including over 1,500 CVC placements found excellent specificity and positive likelihood ratio for confirming CVC placement using US with a positive likelihood ratio (PLR) of 31.12 (CI 14-65) in identifying malposition14. Due to the strength of available evidence, a small, single center randomized trial was conducted in sixty patients undergoing CVC placement in a medical ICU. Placement was confirmed by US in the intervention group and CXR in the control group (CVC malposition was ruled out by visualizing the guidewire in the right atrium). The authors reported a drop in both CXR utilization, by 56%, and time to CVC utilization, by 27 minutes, in the US group15. The sum of current evidence supports US-based CVC confirmation.

Summary

US has become a competing standard with chest x-ray for the confirmation of supra-diaphragmatic CVC placement. When all components of a successful post line placement ultrasound exam are confirmed specificity is high to rule out malposition and pneumothorax (Figure 7). This workflow decreases the necessity for post procedure x-rays and allows for expeditious use of the central line.

AUTHORED BY: HAMZA IJAZ, MD and CHRIS ZALESKY, MD

Drs. Ijaz and Zalesky are both PGY-1’s in the University of Cincinnati Emergency Medicine Residency program.

FACULTY EDITS BY: LORI STOLZ, MD RDMS

Dr. Stolz is an Associate Professor of Emergency Medicine at the University of Cincinnati and Director of the Ultrasound Fellowship.

REFERENCES

1.     Abhishek C, Munta K, Rao SM, Chandrasekhar CN. End-tidal capnography and upper airway ultrasonography in the rapid confirmation of endotracheal tube placement in patients requiring intubation for general anesthesia. Indian Journal of Anesthesia. 2017; 61:486-489.

2.     Chou EH, Dickman E, Tsou PY, … Marshal J. Ultrasonography for confirmation of endotracheal tube placement: a systematic review and meta-analysis. Resuscitation. 2015; 90:97-103.

3.     Gottlieb M, Bailitz J. Can transtracheal ultrasonography be used to verify endotracheal tube placement? Ann Emerg Med. 2015; 66:394-395.

4.     Chou HC, Tseng WP, Wang CH, … Chen SC. Tracheal rapid ultrasound exam (T.R.U.E.) for confirming endotracheal tube placement during emergency intubation. Resuscitation. 2011; 82:1279-1284.

5.     Werner S, Smith C, Goldstein J, … Cydulka R. Pilot study to evaluate the accuracy of ultrasonography in confirming endotracheal tube placement. Ann Emerg Med. 2007; 49:75-80.

6.     Wilson J. (2018). “Endotracheal tube placement and confirmation” Lewiss RE, Jones RA, Strony RJ. Practical Guide to Critical Ultrasound, Volume 2.

7.     Hourmozdi JJ, Markin A, Johnson B, Fleming PR, Miller JB. Routine Chest Radiography Is Not Necessary After Ultrasound-Guided Right Internal Jugular Vein Catheterization. Crit Care Med. 2016;44(9):e804-808.

8.     2.   Esmailian M, Azizkhani R, Najafi N. Saline Flush versus Chest x ray in Confirmation of Central Venous Catheter Placement; a Diagnostic Accuracy Study. Emerg (Tehran). 2017;5(1):e75.

9.     Duran-Gehring PE, Guirgis FW, McKee KC, et al. The bubble study: ultrasound confirmation of central venous catheter placement. Am J Emerg Med. 2015;33(3):315-319.

10.  Saul T, Doctor M, Kaban NL, Avitabile NC, Siadecki SD, Lewiss RE. The Ultrasound-Only Central Venous Catheter Placement and Confirmation Procedure. J Ultrasound Med. 2015;34(7):1301-1306.

11.  Pittiruti M, Lamperti M. Late cardiac tamponade in adults secondary to tip position in the right atrium: an urban legend? A systematic review of the literature. J Cardiothorac Vasc Anesth. 2015;29(2):491-495.

12.  Helland G, Gaspari R, Licciardo S, et al. Comparison of Four Views to Single-view Ultrasound Protocols to Identify Clinically Significant Pneumothorax. Acad Emerg Med. 2016;23(10):1170-1175.

13.  Wilson SP, Assaf S, Lahham S, et al. Simplified point-of-care ultrasound protocol to confirm central venous catheter placement: A prospective study. World J Emerg Med. 2017;8(1):25-28.

14.  Ablordeppey EA, Drewry AM, Beyer AB, et al. Diagnostic Accuracy of Central Venous Catheter Confirmation by Bedside Ultrasound Versus Chest Radiography in Critically Ill Patients: A Systematic Review and Meta-Analysis. Crit Care Med. 2017;45(4):715-724.

15.  Raman D, Sharma M, Moghekar A, Wang X, Hatipoglu U. Utilization of Thoracic Ultrasound for Confirmation of Central Venous Catheter Placement and Exclusion of Pneumothorax: A Novel Technique in Real-Time Application. J Intensive Care Med. 2019;34(7):594-598.