Category: Laboratory tests

Ultrasound-Guided Vascular Access (2025)

~ iEM Education Project Team ~ Leave a comment

by Zackary Funk & Petra Duran-Gehring

Authors
Listen

Introduction

Ultrasound (US) guidance has become an increasingly common technique for vascular access in the Emergency Department (ED), with applications for both central and peripheral lines [1-4]. Initially adopted for central venous catheter (CVC) insertion, particularly in the internal jugular vein, US improved placement success rates, decreased complication rates, and shortened insertion times. As US technology and training advanced, its use expanded to peripheral intravenous line (PIV) placement, where studies have demonstrated increased success rates, reduced complications, and less pain, especially for patients with difficult access [1-4]. Difficult IV access, occurring in 10% to 30% of ED patients—particularly those with morbid obesity, IV drug use, hypovolemia, or chronic illness—can delay cannulation due to multiple failed attempts [5]. Ultrasound-guided PIV placement can mitigate these challenges, with one study reporting an 85% reduction in the need for CVCs in non-critical patients through the implementation of a US-guided PIV catheter program [6]. The overall benefits of US-guided vascular access include improved success rates, fewer complications, decreased pain, reduced time to cannulation, fewer attempts required, and improved patient satisfaction [1-4]. While it may add some complexity compared to landmark or “blind” approaches, the ability to directly visualize target vessels makes US-guided vascular access a highly effective and patient-centered technique.

Indications

Intravenous (IV) access is often critically important for many aspects of patient care in the ED [1-3]. These include:

US-Guided Peripheral IV Access:

  1. Patients who have had three or more blind attempts without successful cannulation.
  2. Patients with a history of difficult IV access.
    • Always evaluate the patient using traditional visual inspection and palpation before preparing for US-guided peripheral IV access. Factors that contributed to difficult IV access during previous encounters, such as hypovolemia, may not be present during subsequent visits.
  3. Patients who have previously required central line placement solely for IV access.
    • As mentioned above, when the clinical situation permits, patients with a history of requiring US-guided vascular access should be evaluated for landmark-based IV sites and/or US-guided peripheral IV sites before proceeding to the more invasive procedure of central venous access.

US-Guided Central Venous Access:
Whenever possible, it is highly recommended to use ultrasound guidance for invasive vascular access procedures, such as central venous cannulation, due to its demonstrated ability to decrease the occurrence of severe complications and increase success rates. The primary indication for ultrasound guidance in central venous access is the need for central venous access itself. Below is a list of specific indications for central venous access [1-4]:

  1. Inability to obtain peripheral IV access required for critical interventions or investigations.
  2. Long-term administration of vasoactive substances (e.g., norepinephrine/epinephrine infusions).
  3. Administration of high-concentration or potentially caustic medications (e.g., hypertonic saline, concentrated or large volumes of potassium chloride).
  4. High-pressure or large-volume infusions, such as massive transfusions in trauma patients with hemorrhagic shock.
  5. Emergent dialysis or plasmapheresis access in patients without established arteriovenous fistulas or other dialysis-capable access.
  6. Transvenous pacemaker placement.

Contraindications

Although there are many benefits of US-guided venous access, some contraindications and considerations should be kept in mind [3,4,7]:

  1. Presence of cellulitis, burns, massive edema, or injuries at or proximal to the proposed insertion sites.
  2. Other injuries, diseases, or anatomical distortions of the affected limb/site that may lead to complications during or after access (e.g., compartment syndrome, extravasation, bleeding from neoplasms, etc.).
  3. Risk of compromised vascular flow distal to the site.
  4. Coagulopathy (considered a relative contraindication).
  5. A capacitated patient declines to undergo the procedure after demonstrating an understanding of the risks and benefits as explained by the care team.

Equipment and Patient Preparation

While the materials and equipment required for peripheral IV access are very similar to those needed for central vascular access, we have separated them into two lists to highlight some key differences. Regardless of the procedure, adherence to hand hygiene practices and the universal use of personal protective equipment are absolutely essential for every procedure.

Equipment for Peripheral IV Access

  • Ultrasound machine equipped with a high-frequency linear probe.
  • Examination gloves.
  • Skin disinfectant (e.g., alcohol swabs, chlorhexidine swabs, povidone-iodine, etc.).
  • Occlusive ultrasound probe cover.
  • Sterile ultrasound gel.
  • Elastic tourniquet.
  • IV catheter.
  • IV securement device and dressing.
  • IV extension tubing and IV port.
  • Normal saline flush.
  • Sharps disposal device/container.
  • Stool or chair (recommended).
Figure 1 - Equipment for Peripheral IV Access

Equipment for Central Venous Access

  1. Ultrasound machine with a high-frequency linear probe.
  2. Sterile gloves.
  3. Eye protection.
  4. Central Venous Catheter Kit (if available), which often includes:
    • Sterile gown.
    • Face mask.
    • Bouffant or scrub cap.
    • Skin disinfectant swabs (e.g., chlorhexidine, povidone-iodine, etc.).
    • Vial of local anesthetic, needle, and syringe.
    • 18-gauge introducer needle and syringe.
    • #11-blade scalpel.
    • Gauze.
    • Guidewire.
    • Dilator(s).
    • Central venous catheter.
    • Sterile saline flush syringes.
    • Needle driver.
    • Suture.
    • Dressing.
    • Sharps disposal hub.
  5. Sterile occlusive ultrasound probe cover sheath.
  6. Sterile ultrasound gel.
  7. IV ports.

Patient Preparation

Proper patient preparation is essential to ensure the accuracy of line placement and minimize patient discomfort or complications. 

Introduction and Identification
Begin by introducing yourself to the patient and confirming their full name. 

Patient History and Consent
Inquire about any allergies, phobias, or a history of fainting during previous IV line procedures. Clearly explain the purpose, benefits, and potential risks of the procedure in simple terms. Once the patient or their next of kin fully understands the information, obtain verbal consent. Note that written consent is not required in emergency situations unless mandated by institutional policy.

Alleviating Anxiety
Address any patient concerns and provide reassurance to help alleviate fear or anxiety. Ensuring the patient is calm can significantly improve their experience and the procedure’s success.

Procedure Steps

Here, we will describe the procedural steps for both ultrasound-guided peripheral intravenous access and ultrasound-guided central vascular access. For each procedure, ensure that the ultrasound machine and probes are in good working order and that there is sufficient power or a reliable power source to successfully and safely complete the procedure. Ultrasound probes should be disinfected before and after each use to protect both patients and providers from exposure to bloodborne and other pathogens, even when sterile probe covers are used. For an overview of the procedural steps for ultrasound-guided peripheral IV access, please review the accompanying video.

Image Acquisition in Vascular Access Procedures

Optimizing the image of the target vessel is critical for procedural safety and success in ultrasound-guided vascular access. This section will describe the general principles and equipment needed to obtain and optimize target visualization.

The high-frequency linear ultrasound probe is most commonly used for vascular access procedures as it provides high-resolution images of superficial structures in the body (Figure 2). Although this resolution comes at the cost of limited penetration into deeper tissues, this limitation is rarely an issue due to specific factors influencing the appropriate depth of target vessels for cannulation, as discussed below.

Figure 2 - Linear Probe (transducer)

The next step is to ensure proper left-right probe orientation. This is accomplished prior to image acquisition by aligning the probe indicator on the ultrasound screen with the probe indicator on the linear probe itself. According to standard convention, the probe indicator on the device screen will appear as a dot, arrow, manufacturer logo, or other marking on the upper left side of the screen (Figure 3a).

Figure 3a - US Probe and Screen Markers

The image nearest the probe indicator on the screen corresponds to the signal emitted from the probe transducer head closest to the physical probe indicator, typically a raised marking or similar feature. A simple technique to confirm orientation involves applying a small amount of ultrasound gel to one side of the probe face, touching this area with a gloved finger, and observing where the movement appears on the screen (Video 1). Once the two markers are aligned, rightward movement on the screen will correspond to movement away from the probe indicator in physical space.

Once orientation is established, perform a survey scan of the site. After applying an elastic tourniquet (if peripheral IV access is being attempted), position the probe perpendicular to the long axis of the extremity or the anticipated course of the target vessel (Figure 4).

Figure 4 - positioning the probe perpendicular to the long axis

This generates a “transverse,” “short-axis,” or “cross-sectional” image of the vessel. If the screen appears too dark to delineate structures, increase the gain setting to brighten the image. Conversely, if the screen is too bright, decrease the gain setting. Vessels should appear as circular structures with a dark or “anechoic” center, indicating blood within the lumen that allows the ultrasound beam to pass through easily (Figure 5).

Figure 5 - increasing the gain setting to brighten the image

Several critical aspects of the target vessel must be assessed during imaging to ensure suitability for cannulation, including vessel type (venous vs. arterial), diameter, depth, patency, and proximity to other structures.

Vessel Assessment: Begin by verifying that the target is a vein. Veins have thinner walls compared to arteries and are compressible. Gentle pressure applied to the vein should cause the walls to collapse inward and meet, confirming its venous nature. Compression also ensures there is no intraluminal obstruction, such as a venous clot (Video 2).

Video 2 – applying pressure to the vessels

Next, assess the vessel’s depth using the depth markers displayed on the ultrasound screen, which typically indicate depth in centimeters. For example, a vessel aligned with the second hash mark from the top of the screen would be located at a depth of 2 cm from the skin surface (Figure 6).

Figure 6 - Measuring the depth of the vessel

Once the depth is measured, determine the vessel diameter, which is essential for selecting the appropriate catheter size for peripheral IV access. Finally, rotate the transducer 90 degrees to visualize the vessel in its long axis, ensuring that the target location is not near a branch point or valve.

Catheter Selection: In peripheral IV access, depth and diameter measurements determine the appropriate catheter size. Peripheral IV catheters vary in diameter (gauge), with smaller gauge numbers indicating larger catheter diameters (e.g., 16G is larger than 22G). A vessel diameter greater than 4 mm (0.4 cm) can accommodate an 18G or smaller catheter without occlusion. 

Figure 7 - Catheters

Catheters also come in various lengths, which affect their stability and suitability for deeper vessels. The depth of the target vessel determines the required catheter length, as longer catheters provide greater stability within the vein [2,3].

Figure 8 - Hypotenuse (needle track), [the image provided by authors]

The needle length required to reach the target vessel can be approximated using the Pythagorean theorem:

a2 + b2 = c2,

where c represents the needle track (hypotenuse. figure 8), a is the vessel depth, and b is the distance from the probe to the needle insertion point. For example, for a vessel 1.2 cm deep with a needle insertion point 1.2 cm distal to the probe, the calculation would be:

1.22 + 1.22 = c2,

resulting in c = 1.69 cm. A simpler method is to multiply the vessel depth by 1.4 (e.g., 1.2 cm × 1.4 = 1.68 cm). To ensure catheter stability within the vein, use the following formula to estimate the necessary catheter length:

Catheter Length = (Vein Depth × 1.4) × 3

This formula accounts for 1/3 of the catheter length reaching the vessel and 2/3 residing within the vein lumen. For example, a 6 cm catheter should not be used for vessels deeper than 1.6 cm.

For peripheral venous access, the following characteristics define an appropriate target vessel for US-guided peripheral IV access:

  • Easily compressible with light pressure applied using the ultrasound probe.
  • Follows a straight path as it travels proximally.
  • Lacks valves that would impede the passage of the cannula or flow after insertion.
  • Diameter greater than 0.4 cm.
  • Close to the skin surface, at a depth of less than 1.6 cm.

For central venous access, the same general principles apply. Regarding vessel diameter and depth, large-diameter vessels that are as superficial as possible are optimal. However, given the nature of these vessels in adult patients and the equipment used for central venous access, the exact parameters regarding diameter and depth mentioned for peripheral vein characteristics do not rigidly apply. Large-diameter vessels such as the internal jugular veins, subclavian veins, and femoral veins are preferred, and access should ideally be attempted at the point where the vessel is located as superficially as possible [4].

Regardless of whether peripheral or central IV access is utilized, the procedure under ultrasound guidance involves dynamically guiding the needle tip to prevent complications. Dynamic cannulation can be performed using either a transverse, out-of-plane approach or a longitudinal, in-plane approach. The transverse view, also known as the out-of-plane approach, is the most commonly used and involves visualizing the needle as a hyperechoic (bright) dot on the ultrasound screen. In contrast, the in-plane approach allows direct visualization of the entire needle length in a long-axis plane but is more challenging for novices, as the needle must remain within the ultrasound beam.

As the metallic needle within the catheter is hyperechoic, it appears as a white dot in the transverse plane and a long hyperechoic line in the longitudinal plane (Figure 9).

Figure 9 - the metallic needle within the catheter is hyperechoic, it appears as a white dot in the transverse plane and a long hyperechoic line in the longitudinal plane

In the transverse plane, it is critical to track the needle tip as it pierces the ultrasound beam, as the appearance of the needle looks the same regardless of its position along the beam. This tracking is achieved by alternating movements of the transducer and the needle. By “leading” with the transducer, then advancing the needle, the tip can be visualized first. Once the needle is seen, advancement should pause, and the transducer should slide slightly proximal up the vein where the needle is no longer visible, after which the needle can be advanced again (Figure 10). This alternating movement allows visualization of the tip as it progresses through the soft tissue and can be repeated until the vein is cannulated (Video 3).

Figure 10a - Walking down the vein: This sequence illustrates the process of "walking down the vein" as observed on an ultrasound. From left to right: the needle initially appears, then disappears, and later re-emerges deeper within the soft tissue before vanishing again. This phenomenon occurs due to the probe moving away, and when the needle reappears, it simply aligns with the ultrasound beam. Note that in real-time, the needle’s positional changes are more gradual than shown here; the figure above is a simplified representation of the concept (refer to the accompanying video for details). [The image was provided by authors].

Video 3 – Walking down the vein

Once the needle is visualized within the vein, the transducer can be rotated to ensure that the needle tip is within the vein lumen and has not pierced the back wall of the vessel. This visualization also allows for redirection of the needle before catheter insertion, ensuring smooth placement when the catheter is advanced off the needle (Video 4). For central venous catheters, a guidewire is inserted after confirming the needle’s position within the vein lumen.

Video 4 – provided by authors

After successfully inserting the IV line, blood return should be verified, and the catheter should be secured in place. As a final confirmation, flush the line. For peripheral IVs, place the ultrasound transducer proximally from the IV site, flush the line, and observe for turbulence or a “glitter artifact” caused by fluid rushing through the vein (Video 5).

Video 5 – provided by authors

This step confirms successful IV cannulation and can also assist in troubleshooting. If the “glitter” does not appear within the vein, the IV catheter is outside the vessel and unusable. For central lines, this confirmation can be performed by visualizing the “glitter” artifact in the right ventricle using the subxiphoid plane within three seconds of flushing the distal port of the line (Video 6).

Video 6 – Glitter Artifact [the video was provided by authors]

Step by Step Guide for US-Guided Peripheral IV Access [3,8]

  1. Verify the identity of the patient who is to undergo IV access and explain the procedure to the patient/healthcare surrogate (when possible).
  2. Position the ultrasound machine on the same side of the patient as the operator.
  3. Don examination gloves.
  4. Clean the ultrasound probe with institution-approved disinfectant.
  5. Remove gloves and replace with clean gloves.
  6. Position stool/chair and adjust the ultrasound machine for the best screen viewing when obtaining access.
  7. Apply an elastic tourniquet proximal to the site to be screened for potential access sites.
  8. Apply ultrasound gel to the target area and orient the probe perpendicularly to the patient’s extremity to obtain a transverse/short-axis view of the target vessels.
  9. Orient the probe indicator to match the orientation displayed on the ultrasound screen, with both conventionally indicating the patient’s right side (Figure 3a).
  10. Assess potential veins for appropriate depth, diameter, and patency.
  11. Veins should:
    • Be greater than or equal to 0.4 cm in diameter for an 18G catheter.
    • Be less than 1.6 cm in depth for a 6 cm length catheter.
    • Be easily compressible without evidence of clots, valves, or other obstructions to blood flow.
  12. Clean off ultrasound gel and release the tourniquet.
  13. Clean the selected site with skin disinfectant and allow it to air dry per manufacturer instructions.
  14. Set up supplies (prepare IV catheter, securement device, port, flush, and dressing).
  15. Cover the ultrasound probe with an occlusive cover.
  16. Avoid touching the head of the probe or the portion of the cover that will contact the patient’s skin.
  17. Reapply the tourniquet and ensure the patient’s arm remains in the appropriate position.
  18. Apply sterile ultrasound gel to the site.
  19. Do not touch the site with gloves or allow uncleaned materials/surfaces to come into contact with the site.
  20. If the site is potentially contaminated, remove the gel and clean the site again before attempting vascular access.
  21. Position the probe and locate the target vein again.
  22. At approximately a 45-degree angle, puncture the skin underneath the ultrasound probe head, observing on ultrasound for the needle tip in the subcutaneous tissue.
  23. Once the needle tip has been visualized, slide the probe proximally away from the needle tip.
  24. Once the needle tip is no longer visualized on ultrasound, carefully advance the needle in 1-2 mm increments until the needle tip returns into view on ultrasound.
  25. Repeat this alternating probe-needle advance until the needle has been advanced into the target vessel (Video 3).
  26. Decrease the angle of the needle as needed to continue advancing the needle in the alternating probe-needle manner within the vessel, keeping the needle tip in the center of the vessel lumen.
  27. Once the needle has been advanced several millimeters into the target vessel, anchor the hand holding the needle to ensure it does not advance further and lay down the ultrasound probe.
  28. Keeping the needle still, advance the catheter over the needle into the vessel.
  29. Once the catheter has been advanced, keep the catheter in place with the hand which advanced the catheter and use the other hand to carefully remove the needle.
  30. Ensure the safety needle capping mechanism on the needle has activated (if automatic upon needle removal from catheter) or activate the safety needle capping mechanism (if not designed to engage automatically) and dispose of the needle into a designated sharps container.
  31. Attach extension tubing and port to the catheter hub (some catheters come with the extension tubing and hub pre-attached).
  32. Clean any remaining ultrasound gel or blood from the access site and secure the catheter with an occlusive dressing.
  33. Attach a saline flush to the hub.
  34. If any air remains in the catheter extension tubing (if applicable), be sure to aspirate any air prior to attempting to flush the line.
  35. Retrieve the ultrasound probe and place it along the vessel proximal on the extremity to the catheter.
  36. After confirming the absence of air in the catheter and extension tubing, flush several cc’s of crystalloid solution through the catheter.
  37. If the catheter is in the correct position and functioning correctly, a “glitter” artifact effect should be visualized within several seconds of pushing the fluid through the catheter (Video 6).
  38. Dispose of supplies in appropriate containers and clean the ultrasound probe with disinfectant wipes.
  39. Remove gloves and wash hands.
  40. Document the access site in the patient’s chart, including site location, catheter gauge, time placed, and operator placing the line.
  41. Ensure you and your team frequently assess the site and extremity for evidence of extravasation, hematoma formation, or other complications.

Step by Step Guide for US-Guided Central Venous Access [4,9]

  1. Verify the identity of the patient who is to undergo IV access and explain the procedure to the patient/healthcare surrogate (when possible).
  2. Position the ultrasound machine on the opposite side of the patient as the operator in the operator’s line of sight.
  3. Don examination gloves.
  4. Clean the ultrasound probe with institution-approved disinfectant.
  5. Remove gloves and replace with clean gloves.
  6. Apply ultrasound gel to the target area and orient the probe perpendicularly to the patient’s extremity to obtain a transverse/short-axis view of the target vessels.
  7. Orient the probe indicator to match the orientation displayed on the ultrasound screen, with both conventionally indicating the patient’s right side (Figure 3a).
  8. Assess potential veins for appropriate depth, diameter, and patency:
  9. Veins should:
    • Be greater than or equal to 0.4 cm in diameter for an 18G catheter.
    • Be less than 1.6 cm in depth for a 6 cm length catheter.
    • Be easily compressible without evidence of clots, valves, or other obstructions to blood flow.
  10. Clean off ultrasound gel.
  11. Clean the selected site with skin disinfectant and allow it to air dry per manufacturer instructions.
  12. Open the central venous catheter kit (or, if unavailable, establish a sterile field upon which to place sterile equipment).
  13. Don eye protection, face mask, and bouffant/scrub cap.
  14. Don a sterile gown and gloves.
  15. Drape the patient in a sterile fashion.
  16. Place the dominant hand within a sterile ultrasound probe cover (if rubber bands to secure the sheath to the probe are included, consider applying rubber bands around the thumb of the dominant hand before placing the hand within the sheath).
  17. Apply sterile gel to the inside of the sheath, which will contact the ultrasound probe head.
  18. Have an assistant pass the linear probe and grab the probe head with the dominant hand surrounded by the ultrasound probe sheath.
  19. Carefully extend the sheath around the probe. Once able, ask an assistant to grab the open end of the probe sheath and pull it toward them along the probe’s wire until it is well away from the sterile field. The assistant can gently release the probe wire now covered in the sheath, being careful not to let the contaminated end of the probe cover touch the sterile field.
  20. Apply the rubber bands (if applicable) to the head of the probe and smooth any air bubbles or irregularities which may have formed along the transducer surface while inserting the probe.
  21. Draw up several cc’s of local anesthetic into a syringe.
  22. Apply sterile ultrasound gel to the target site and confirm there has been no change in positioning of the target vessel during setup.
  23. Inject the local anesthetic into the skin and along the track of the needle to the target vessel, being sure to aspirate before each injection.
  24. It is recommended that the injection of the local anesthetic be performed under active ultrasound guidance to minimize the chance of accidental injection into the vessel and to confirm the anesthetic is applied along the intended tract of the needle.
  25. Ensure that air bubbles have been removed from the local anesthetic solution prior to injection, as these air bubbles will distort visualization of the target vessel area due to scattering of the ultrasound beam as it comes into contact with air.
  26. While the local anesthetic takes effect, flush the lumens of the catheter with saline to prevent the introduction of air into the patient’s vasculature and test that the guidewire feeds smoothly and is free of kinks or defects.
  27. With the introducer needle at an approximately 45-degree angle, puncture the skin underneath the ultrasound probe head, observing on ultrasound for the needle tip in the subcutaneous tissue.
  28. Once the needle tip has been visualized, slide the probe proximally away from the needle tip.
  29. Once the needle tip is no longer visualized on ultrasound, carefully advance the needle in 1-2 mm increments until the needle tip returns into view on ultrasound (Figure 8).
  30. Repeat this alternating probe-needle advance until the needle has been advanced into the target vessel, pulling back on the needle plunger to aspirate blood upon entry into the vessel.
  31. Decrease the angle of the needle as needed to continue advancing the needle in the alternating probe-needle manner within the vessel, keeping the needle tip in the center of the vessel lumen.
  32. Once the needle has been advanced several millimeters into the target vessel, anchor the hand holding the needle to ensure it does not advance further and lay down the ultrasound probe.
  33. Keeping the needle still, lay down the ultrasound probe, remove the syringe from the needle, and retrieve the guidewire.
  34. Advance the guidewire through the introducer needle approximately 20 cm, ensuring that it passes freely without resistance. If resistance is encountered, stop advancing immediately and assess the situation.
  35. Keeping one hand on the guidewire at all times, withdraw the introducer needle over the guidewire and place it in a sharps disposal device or bin.
  36. Confirm that the guidewire is in the target vessel using ultrasound to visualize the guidewire in the vessel in long-axis (Figure 9).
  37. Place gauze nearby the guidewire insertion site for use in the upcoming step.
  38. Place the dilator over the guidewire and advance it toward the skin, stopping several centimeters above the skin.
  39. Using the scalpel, make a small linear incision with the blade directed away from the guidewire and the patient. Consider placing gauze over the site after the incision to minimize bleeding.
  40. Using the dominant hand, insert the dilator to the approximate depth of the vessel visualized on ultrasound, using the other hand to hold the guidewire.
  41. It is recommended to use a twisting motion while advancing the dilator with the hand gripping the dilator just above the patient’s skin.
  42. Ensure that the guidewire remains stationary during dilatory insertion.
  43. Remove the dilator over the guidewire and thread the central venous catheter over the guidewire.
  44. Advance the catheter into the vessel over the guidewire while keeping one hand on the guidewire at all times.
  45. The guidewire should emerge from the distal port of the catheter (typically marked with a brown hub and located in the center of the available ports).
  46. Once the catheter has been placed at the appropriate depth into the target vessel, aspirate blood using a syringe from all ports to ensure patency.
  47. Flush all ports with saline to minimize the chance of clotting.
  48. Use the needle driver and suture to secure the line in place.
  49. Clean the site once more and apply an institution-approved antimicrobial dressing.
  50. If the line was placed in an internal jugular or subclavian vein site, obtain a post-procedural chest radiograph to confirm appropriate placement and assess for complications (e.g., pneumothorax).
Figure 9 - Guide-wire in the vessel - long axis view

Complications

Ultrasound-guided venous access, while generally safer than traditional landmark techniques, still carries potential complications, both for peripheral and central line placement.

Complications of US-Guided Peripheral IV Access [1-3,8]

Infiltration/Extravasation: This is a common complication where IV fluid or medication leaks into the surrounding tissue instead of flowing into the vein. It is a leading cause of catheter failure and may occur more frequently with deep brachial veins compared to other antecubital veins. Using a longer catheter can help minimize the risk of infiltration.

Catheter Dislodgement: Catheter dislodgement occurs when the catheter moves out of the vein, leading to loss of venous access and potential extravasation. This complication is more common with deep veins compared to superficial veins. To reduce the risk, it is essential to ensure that a sufficient length of the catheter is properly positioned within the vessel.

Thrombophlebitis: Thrombophlebitis refers to the inflammation of the vein, which may occur during or after IV placement.

Infection: Although studies have shown no increased infection rates with ultrasound guidance compared to traditional methods, the risk of infection remains. Using sterile gel and adhering to proper cleaning techniques can significantly reduce this risk.

Damage to Adjacent Structures: There is a risk of damaging nearby structures, such as arteries and nerves, during peripheral IV placement. This risk is heightened when using deep veins, which are often located closer to these critical structures.

Posterior Vessel Wall Puncture: The short-axis technique, commonly used during ultrasound-guided IV access, has been associated with a higher risk of puncturing the posterior (back) wall of the vessel.

Hematoma: Bleeding and hematoma formation can occur as a result of vein trauma during catheter placement.

Premature Catheter Failure (PCF): Premature catheter failure occurs when the catheter fails within 24 hours of placement. Studies suggest that PCF rates are higher in ultrasound-guided cannulations compared to traditional methods. Common causes include infiltration, dislodgement, and thrombophlebitis.

Complications of Ultrasound-Guided Central Venous Catheter (CVC) Access [4,9,10]

Arterial Puncture/Cannulation: Accidental puncture or cannulation of an artery, such as the carotid artery during internal jugular vein access, is a serious complication. This risk can be mitigated by using real-time ultrasound guidance and ensuring careful visualization of surrounding structures.

Hematoma: Bleeding and hematoma formation are potential complications during central venous catheter placement, especially if there is accidental puncture of surrounding tissues.

Pneumothorax: A collapsed lung (pneumothorax) is a known complication, particularly during subclavian vein access. Ensuring proper technique and real-time imaging can help reduce this risk.

Hemothorax: Bleeding into the pleural space (hemothorax) may occur during central venous access, especially if there is inadvertent damage to vascular structures near the pleural cavity.

Infection: Catheter-related bloodstream infections are a significant risk associated with central lines. Adherence to strict aseptic technique, including the use of sterile drapes, gloves, and probe covers, is essential to minimize this risk.

Thrombosis: Deep vein thrombosis and catheter-related bloodstream infections can occur as a result of CVC placement. Proper placement, routine monitoring, and prompt intervention are critical in reducing this risk.

Nerve Injury: There is a risk of nerve damage, such as brachial plexus injury, during internal jugular vein catheterization. Careful visualization of anatomical landmarks using ultrasound is critical to avoid this complication.

Catheter Malposition: The catheter may be unintentionally placed in an incorrect location, leading to functional and clinical complications. Real-time imaging during and after placement can ensure proper positioning of the catheter.

Air embolism: It is a rare but serious complication associated with both peripheral and central vein catheterization, which can cause significant neurological deficits and seizures if not promptly diagnosed and treated. The pathophysiology involves air entering the venous system due to a pressure gradient between the atmosphere and the veins, which can occur during catheter insertion, maintenance, or removal. The risk of air embolism is heightened by improper patient positioning. In cases of massive air embolism, immediate interventions such as resuscitation, positioning the patient in the left lateral decubitus and Trendelenburg position, and using hyperbaric oxygen therapy or extracorporeal membrane oxygenation can be life-saving.

Hints and Pitfalls

Universal safety precautions are critical for every procedure. This includes the consistent use of personal protective equipment (PPE) and cleaning all equipment before and after use. These practices are essential to protect both the operator and the patient from harm, including the risk of infections or cross-contamination.

Preparation is paramount to ensuring procedural success and minimizing complications. Proper assessment of the target vessel, including its depth, diameter, and patency, along with setting up the necessary equipment in advance, significantly increases the chances of success during cannulation. Needle tip visualization is also crucial throughout the procedure to prevent iatrogenic injuries caused by inadvertently advancing the needle tip into non-target structures near the vessel.

If a cannulation attempt fails or if the intravenous (IV) line fails due to infiltration, subsequent attempts should ideally be made at a different site to avoid cumulative damage to the same area. If a new site cannot be used, attempts should occur proximal to the initial site.

Strategies to Reduce Complications [1-3, 7-10]

Adequate training is a cornerstone of safe and successful ultrasound-guided venous access. Providers must be proficient in real-time ultrasound guidance techniques, which allow precise needle advancement and proper placement. Additionally, sterile technique is essential during all stages of the procedure, including the use of sterile gel and probe covers to minimize infection risk.

Choosing the appropriate vein for cannulation is another key strategy to reduce complications. This decision should be based on careful vein selection, including evaluating its accessibility and suitability for the intended catheter size. Proper catheter length and size selection are equally important, with tools like the Pythagorean theorem aiding in determining the optimal catheter length for stable placement within the vessel.

Visualization of the needle tip during insertion is vital to avoid injury to surrounding structures. The long-axis approach can provide continuous visualization of the needle tip, ensuring accurate placement within the vessel lumen. After catheter placement, ultrasound can confirm the catheter’s position and patency, reducing the risk of complications such as malposition or infiltration.

Post-procedural monitoring is just as important as the procedure itself. Regular assessment of the insertion site is necessary to detect early signs of infection, thrombophlebitis, or other complications, allowing for timely intervention if needed.

Special Patient Groups

Pediatrics

US-guided venous access in pediatric patients has been shown to significantly enhance the success rates and reduce complications associated with vascular access procedures. A retrospective analysis of 1028 US-guided central vascular access procedures in children demonstrated a high success rate of 97.2%, with the left brachiocephalic vein showing a higher success rate than the right [11]. The integration of ultrasound guidance in pediatric venous access procedures is associated with improved outcomes, emphasizing its role as a preferred method in clinical practice.

Geriatrics

US-guided venous access in geriatric patients has been shown to be a highly effective and safe method for catheter placement. The use of ultrasound guidance significantly reduces failure (success rate of 96.36%) and complication rates (7.27%) [12]. US-guided peripherally inserted central catheter insertion in elderly patients also reported high success rate, with minimal complications [13]. The use of ultrasound guidance for internal jugular vein catheterization further supports its efficacy in reducing failure and complication rates for central venous port placement [14]. Overall, the integration of ultrasound guidance in venous access procedures for geriatric patients enhances safety, reliability, and patient outcomes, making it a valuable tool in the management of this vulnerable population [12-14].

Pregnant patients

US-guided venous access provides significant benefits for pregnant patients, particularly by reducing complications and improving procedural success. Real-time ultrasonographic imaging enables clear visualization of target vessels, which is especially critical in cases of challenging anatomy during pregnancy [15]. This approach aligns with the growing adoption of point-of-care ultrasound (POCUS) to enhance success rates in both peripheral and central venous catheterization. By improving patient safety and minimizing complications, ultrasound guidance has become an essential tool for optimizing venous access procedures and ensuring safer care for pregnant patients [16].

Authors

Picture of Zackary Funk

Zackary Funk

Picture of Petra Duran-Gehring

Petra Duran-Gehring

Petra Duran-Gehring M.D., graduated from medical school at LSU Health Sciences Center in New Orleans, and completed her residency in emergency medicine at the University of Florida College of Medicine – Jacksonville. She achieved certification through the American Registry of Diagnostic Medical Sonographers and founded the emergency ultrasound program for the department of emergency Medicine at UFCOMJ. She is a nationally recognized leader in emergency ultrasound education and research, including serving as co-director of the ACEP Ultrasound Management Course, and director for the SEMPA Ultrasound Course. She has lectured throughout the country, and has received numerous teaching awards. When not teaching ultrasound, she loves spending time with her husband and three young sons.

Listen to the chapter

References

  1. Duran-Gehring P. Ultrasound-Guided IV Access. The Essential Emergency Ultrasound Course; 2019. Accessed August 5, 2023.
  2. Duran-Gehring P, Bryant L, Reynolds JA, Aldridge P, Kalynych CJ, Guirgis FW. Ultrasound-Guided Peripheral Intravenous Catheter Training Results in Physician-Level Success for Emergency Department Technicians. J Ultrasound Med. 2016;35(11):2343-2352. doi:10.7863/ultra.15.11059
  3. Gottlieb M, Sundaram T, Holladay D, Nakitende D. Ultrasound-Guided Peripheral Intravenous Line Placement: A Narrative Review of Evidence-based Best Practices. West J Emerg Med. 2017;18(6):1047-1054. doi:10.5811/westjem.2017.7.34610
  4. Leung J, Duffy M, Finckh A. Real-time ultrasonographically-guided internal jugular vein catheterization in the emergency department increases success rates and reduces complications: a randomized, prospective study. Ann Emerg Med. 2006;48(5):540-547. doi:10.1016/j.annemergmed.2006.01.011
  5. Jacobson AF, Winslow EH. Variables influencing intravenous catheter insertion difficulty and failure: an analysis of 339 intravenous catheter insertions. Heart Lung. 2005;34(5):345-359. doi:10.1016/j.hrtlng.2005.04.002
  6. Au AK, Rotte MJ, Grzybowski RJ, Ku BS, Fields JM. Decrease in central venous catheter placement due to use of ultrasound guidance for peripheral intravenous catheters. Am J Emerg Med. 2012;30(9):1950-1954. doi:10.1016/j.ajem.2012.04.016
  7. Shokoohi H, Armstrong P, Tansek R. Emergency department ultrasound probe infection control: challenges and solutions. Open Access Emerg Med. 2015;7:1-9. Published 2015 Jan 5. doi:10.2147/OAEM.S50360
  8. Blanco P. Ultrasound-guided peripheral venous cannulation in critically ill patients: a practical guideline. Ultrasound J. 2019;11(1):27. Published 2019 Oct 17. doi:10.1186/s13089-019-0144-5
  9. Saugel B, Scheeren TWL, Teboul JL. Ultrasound-guided central venous catheter placement: a structured review and recommendations for clinical practice. Crit Care. 2017;21(1):225. Published 2017 Aug 28. doi:10.1186/s13054-017-1814-y
  10. Parienti JJ, Mongardon N, Mégarbane B, et al. Intravascular Complications of Central Venous Catheterization by Insertion Site. N Engl J Med. 2015;373(13):1220-1229. doi:10.1056/NEJMoa1500964
  11. D’Alessandro P, Siffredi JI, Redondo Pertuz E, et al. Retrospective analysis of 1028 ultrasound-guided central vascular access in neonates and children. J Vasc Access. Published online September 26, 2024. Doi:10.1177/11297298241278385
  12. Sun X, Zhang Y, Yang C, et al. Ultrasound-guided totally implantable venous access device through the right innominate vein in older patients is safe and reliable. Geriatr Gerontol Int. 2019;19(3):218-221. doi:10.1111/ggi.13611
  13. Nakano Y, Kondo T, Murohara T, Yamauchi K. Option of Using Peripherally Inserted Central Catheters in Elderly Patients With Dementia: An Observational Study. Gerontol Geriatr Med. 2020;6:2333721420906922. Published 2020 Feb 18. doi:10.1177/2333721420906922
  14. Canfora A, Mauriello C, Ferronetti A, et al. Efficacy and safety of ultrasound-guided placement of central venous port systems via the right internal jugular vein in elderly oncologic patients: our single-center experience and protocol. Aging Clin Exp Res. 2017;29(Suppl 1):127-130. doi:10.1007/s40520-016-0680-9

Reviewed and Edited By

Picture of Arif Alper Cevik, MD, FEMAT, FIFEM

Arif Alper Cevik, MD, FEMAT, FIFEM

Prof Cevik is an Emergency Medicine academician at United Arab Emirates University, interested in international emergency medicine, emergency medicine education, medical education, point of care ultrasound and trauma. He is the founder and director of the International Emergency Medicine Education Project – iem-student.org, chair of the International Federation for Emergency Medicine (IFEM) core curriculum and education committee and board member of the Asian Society for Emergency Medicine and Emirati Board of Emergency Medicine.

Arterial Blood Gas Sampling (2025)

~ iEM Education Project Team ~ Leave a comment

by Gan Kiat Kee & Arif Alper Cevik

Authors
Listen

Introduction

Arterial blood gas (ABG) sampling is a critical procedure performed in the emergency department (ED) that involves obtaining blood from a peripheral artery to assess a patient’s respiratory and metabolic status. This technique is essential for diagnosing and managing various acute conditions, particularly in critically ill patients. The common sites for ABG sampling include the radial, brachial, femoral, and dorsalis pedis arteries. The radial artery is often preferred due to its accessibility and the presence of collateral circulation, which minimizes the risk of complications [1]. ABG sampling can be performed via a single percutaneous needle puncture or through an indwelling catheter for repeated measurements, which is particularly useful in ongoing monitoring of patients with unstable conditions [2].

The analysis of ABG provides vital information regarding the patient’s acid-base balance and respiratory function. Key parameters measured include the partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2), pH, and bicarbonate (HCO3) levels. These measurements are crucial for evaluating the efficacy of gas exchange in the lungs and the metabolic status of the patient [3]. For instance, a low pH coupled with elevated PaCO2 may indicate respiratory acidosis, while a low HCO3 may suggest metabolic acidosis. Additionally, advanced blood gas analyzers can provide further insights by measuring total hemoglobin (tHb), oxyhemoglobin saturation (HbO2), and dysfunctional hemoglobins such as methemoglobin (MetHb) and carboxyhemoglobin (COHb), which are particularly relevant in cases of carbon monoxide poisoning or other hemoglobinopathies [3].

The ability to interpret ABG results is an essential skill for healthcare professionals, particularly in emergency settings where rapid decision-making is crucial. Medical trainees are encouraged to gain proficiency in ABG sampling and interpretation under supervision, as these skills are fundamental to the effective management of patients experiencing respiratory distress, shock, or metabolic derangements [1].

Figure 1 - An example of an arterial blood gas analysis result (Courtesy of Gan Kiat Kee)

Indications

ABG sampling is primarily indicated for evaluating the adequacy of oxygenation and ventilation in patients. By measuring the partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2), healthcare providers can assess respiratory function and the effectiveness of gas exchange in the lungs. For instance, a low PaO2 may indicate hypoxemia, necessitating immediate intervention, while elevated PaCO2 can signify respiratory failure or impaired ventilation [4]. This immediate assessment is crucial in emergencies such as acute respiratory distress or exacerbations of chronic obstructive pulmonary disease (COPD), where timely identification of respiratory compromise can significantly influence patient outcomes [5].

In addition to evaluating oxygenation and ventilation, ABG sampling is essential for identifying and monitoring acid-base disturbances. The measurement of pH, PaCO2, and bicarbonate (HCO3) levels provides critical information regarding the patient’s metabolic and respiratory status. For example, an acidic pH coupled with elevated PaCO2 may suggest respiratory acidosis, commonly seen in conditions such as acute asthma attacks or severe pneumonia [6]. Conversely, metabolic acidosis may be indicated by a low pH with normal or low PaCO2 levels, often observed in patients with diabetic ketoacidosis or renal failure. Monitoring these parameters can guide therapeutic decisions and help clinicians tailor interventions to restore acid-base balance effectively [6].

Furthermore, ABG sampling plays a significant role in detecting and quantifying abnormal hemoglobin levels, such as methemoglobin (MetHb) and carboxyhemoglobin (COHb). These conditions can arise from exposure to certain chemicals or gases, and their identification is critical in emergency settings. For instance, elevated COHb levels indicate carbon monoxide poisoning, which requires immediate treatment [7]. The ability to quickly diagnose such abnormalities through ABG sampling can be life-saving, particularly in cases of suspected toxic exposure.

Lastly, ABG sampling is invaluable in assessing the response to therapeutic interventions, particularly in hypoxic patients receiving oxygen therapy. By comparing pre- and post-intervention ABG values, clinicians can evaluate the effectiveness of treatments and make necessary adjustments to optimize patient care. In situations where venous sampling is not feasible due to the patient’s condition or the urgency of the situation, ABG sampling serves as a critical alternative for obtaining essential blood gas information [4].

Contraindications

Certain contraindications must be considered to ensure patient safety and the accuracy of results. One primary contraindication is the presence of a known deficiency in collateral circulation, which can be assessed using the modified Allen’s test. An abnormal result indicates insufficient blood flow to the hand, increasing the risk of ischemia if an artery is punctured [8-10]. Therefore, performing an ABG in such cases could lead to serious complications, including limb ischemia or necrosis.

In addition to collateral circulation issues, the presence of local infections at the puncture site is another significant contraindication. An infected site can introduce pathogens into the bloodstream, leading to systemic infections or further complications for the patient [11]. Moreover, anatomical abnormalities such as full-thickness burns, arteriovenous fistulas, stents, or vascular grafts at the puncture site can complicate the procedure and increase the risk of complications. These malformations may alter normal blood flow patterns or make it difficult to locate the artery accurately, which can lead to unsuccessful attempts or injury to surrounding structures [8-10].

Severe peripheral vascular disease, including conditions like Buerger’s disease or limb ischemia, also serves as a contraindication for ABG sampling. In patients with these conditions, blood flow to the extremities is already compromised, and the additional trauma of arterial puncture could exacerbate ischemic symptoms [12]. Lastly, patients suffering from active Raynaud syndrome should be excluded from ABG sampling, as the procedure could trigger or worsen their vasospastic episodes, leading to further complications [13].

Some conditions may pose relative contraindications [8-10] to this procedure. Patients with Raynaud disease may experience exacerbated symptoms during and after the puncture, potentially resulting in complications such as ischemia or necrosis at the site of the arterial puncture [14]. Furthermore, even in the absence of spasm, individuals with a history of Raynaud disease may have altered peripheral vascular function, increasing the likelihood of complications during ABG sampling.

Another important relative contraindication is the presence of poor peripheral perfusion, which can severely affect the ability to obtain an adequate blood sample. In patients with compromised perfusion, such as those in shock or with peripheral vascular disease, the risk of inadequate sampling and subsequent complications at the puncture site is elevated. Poor perfusion can lead to difficulties in locating the artery, increasing the risk of multiple punctures and subsequent tissue trauma [15]. Thus, clinicians must assess the patient’s peripheral circulation before proceeding with ABG sampling to avoid unnecessary complications.

Additionally, patients with supratherapeutic anticoagulation or those receiving thrombolytic agents, such as streptokinase or tissue plasminogen activator, represent another group with relative contraindications for ABG sampling [16]. The risk of bleeding complications in these patients is significantly heightened due to their altered coagulation status. Similarly, individuals with existing coagulopathy should be approached with caution, as the likelihood of significant bleeding increases, which could lead to hematoma formation or other vascular complications. In these cases, the clinical necessity of obtaining an ABG sample must be carefully weighed against the potential risks involved, and alternative methods of assessment should be considered if appropriate.

Equipment and Patient Preparation

Equipment

The equipment used in ABG sampling includes the following [16]:

  • Gloves: Non-sterile gloves may be used, but it is essential to avoid touching the puncture site after the area has been cleaned.
  • Syringe for Sampling: A standard syringe with a 25-gauge needle and a 3-mL capacity is preferred. Using a higher-capacity syringe may reduce maneuverability, while smaller needles may increase the risk of traumatic hemolysis, potentially affecting the accuracy of hemoglobin and potassium measurements. A 23-gauge needle may also be used.
  • Lithium Heparin: Aspirate 1-2 mL of lithium heparin (1000 U/mL) into the syringe through the needle and then expel it. Leave the plunger depressed to allow arterial blood flow to fill the syringe.
  • Pre-Heparinized ABG Syringe (Alternative): Many ABG kits include a prefilled heparinized syringe with features like a protective needle sleeve and a syringe cap. Some syringe models have vented plungers that enable presetting a specific blood volume; for these, the plunger is positioned midway in the syringe before the puncture and not pulled back during the procedure. Expel the prefilled heparin before repositioning the vented plunger at the 2-mL mark.
  • Antiseptic Skin Solution: Commonly used solutions include chlorhexidine, povidone-iodine, or 70% isopropyl alcohol.
  • Needle and Syringe for Local Anesthesia (Optional): A 25-gauge needle with a syringe and 1% lidocaine hydrochloride without epinephrine may be used for local anesthesia if needed.
  • Sterile Gauze and Adhesive Bandage: Sterile gauze (2 × 2 inches or 5 × 5 cm) is used to cover the puncture site, secured with an adhesive bandage after sample collection.
  • Syringe Cap: Usually included in ABG kits to seal the syringe after sampling.
  • Sharps Container: A container specifically designed for the safe disposal of needles and other sharp objects.
  • Ice Bag: A bag with crushed ice to transport the sample to the laboratory if point-of-care analysis is unavailable.
  • Non-Sterile Apron: Optional protective clothing to maintain hygiene during the procedure.
  • Rolled Towel: Used to position the hand optimally for the procedure.

Site Selection

Arterial blood gas sampling requires selecting an appropriate site for puncture based on accessibility, patient tolerance, and anatomical considerations. Below are the common sites used for ABG sampling [17]:

Radial Artery
The radial artery is the preferred site for ABG sampling due to its superficial location, good collateral blood supply, and better patient tolerance. It is located medial to the radial styloid process and lateral to the flexor carpi radialis tendon, approximately 2-3 cm proximal to the ventral surface of the wrist crease. The artery can be palpated between the styloid process of the radius and the flexor carpi radialis tendon with the wrist extended.

Radial Artery - Resource: Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Gray528.png

Brachial Artery
The brachial artery is harder to access due to its deeper location compared to the radial artery. It is best identified in the antecubital fossa, medial to the biceps tendon, with the shoulder abducted, elbow extended, and the forearm supinated with the palm facing upward. The needle is typically inserted at a 30° angle just above the elbow crease. Higher up, the artery can also be palpated in the groove between the biceps and triceps tendons. The basilic vein and brachial nerve are located in close proximity to this artery.

Brachial Artery - Resource: Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Brachial_a.png

Femoral Artery
The femoral artery is ideal in cases where the radial and brachial arteries are inaccessible. It is located in the midline between the symphysis pubis and the anterior superior iliac crest, approximately 2-4 cm distal to the inguinal ligament. The artery can be palpated just below the midpoint of the inguinal ligament with the lower limb extended and the patient in a supine position. Needle insertion is performed just below the inguinal ligament at a 90° angle. The femoral artery lies medial to the femoral nerve and lateral to the femoral vein.

Femoral Artery - Resource: Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Femoral-artery-grays-illustrations.jpg

Dorsalis Pedis Artery
The dorsalis pedis artery is a less commonly used site for ABG sampling. It can be palpated lateral to the extensor tendon at the midfoot level. This site is generally reserved for specific clinical scenarios where other arteries are not accessible.

Dorsalis Pedis Artery - Resource: Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Art%C3%A8res_de_la_face_dorsale_du_pied.jpg

Each site has its unique anatomical landmarks and considerations, which should be carefully evaluated to ensure accuracy and minimize complications during the procedure.

Patient Preparation

Proper patient preparation is essential to ensure the accuracy of radial artery blood gas sampling and minimize patient discomfort or complications. Below are the key steps to prepare the patient for the procedure [16,17]:

Introduction and Identification
Begin by introducing yourself to the patient and confirming their full name. Verify that the details on the laboratory form match the patient’s identity to prevent errors.

Patient History and Consent
Inquire about any allergies, phobias, or a history of fainting during previous injections or blood collection. Clearly explain the purpose, benefits, and potential risks of the procedure in simple terms. Once the patient or their next of kin fully understands the information, obtain verbal consent. Note that written consent is not required unless mandated by institutional policy.

Alleviating Anxiety
Address any patient concerns and provide reassurance to help alleviate fear or anxiety. Ensuring the patient is calm can significantly improve their experience and the procedure’s success.

Procedure Steps

The following steps outline the procedure for radial artery blood gas sampling, as recommended by W.H.O. guidelines [16,17]:

Patient Introduction and Identification
Approach the patient, introduce yourself, and confirm the patient’s full name. Verify the details on the laboratory form to ensure accurate identification.

Patient Positioning
Place the patient in a comfortable supine position on a firm surface. For radial artery sampling, ensure the arm is resting comfortably with the forearm supinated and the wrist dorsiflexed at approximately 40°. A rolled towel or gauze roll can be placed under the wrist to improve comfort and elevate the radial artery to a more superficial position. Avoid excessive wrist extension to prevent interference from flexor tendons, which could make pulse detection challenging.

Assess Collateral Circulation
Perform a modified Allen test to assess collateral circulation of the radial artery. If the test fails, repeat it on the other hand. Once an adequate site is identified, note the anatomical landmarks for accurate needle placement. If re-palpation is required, ensure sterile gloves are worn.

  • Preparation of Equipment and Work Area
    Perform hand hygiene, prepare a clean work area, and gather all necessary equipment. Don an impervious gown or apron and face protection if there is a risk of blood exposure.

  • Site Disinfection
    Disinfect the chosen puncture site using an antiseptic skin solution such as chlorhexidine or povidone-iodine. Allow the area to air dry completely before proceeding.

  • Needle and Syringe Assembly
    If the needle and syringe are not preassembled, prepare them by attaching the heparinized syringe to the needle and setting the syringe plunger to the required fill level recommended by the laboratory.

  • Needle Insertion
    Hold the syringe and needle like a dart, with the needle bevel facing upward. Use your index finger to palpate the radial pulse, then inform the patient about the puncture. Insert the needle at a 30º–45º angle approximately 1 cm distal to the palpating finger to avoid contamination of the puncture site.

  • Blood Collection
    Advance the needle into the radial artery until a flashback of blood is observed. Allow the syringe to fill passively with 2–3 mL of arterial blood without pulling back the plunger.

  • Needle Withdrawal and Hemostasis
    After withdrawing the required amount of arterial blood, remove the needle while simultaneously applying firm pressure to the puncture site with sterile gauze. Maintain pressure until hemostasis is achieved. For patients without anticoagulation or coagulopathy, this typically takes 3–5 minutes, while anticoagulated patients or those with bleeding disorders or hypertension may require up to 10–15 minutes of continuous pressure. Avoid checking the puncture site prematurely, as this can increase the risk of hemorrhage or hematoma formation. 

  • Needle Safety and Specimen Handling
    Activate the needle safety mechanism to cover the needle or use a one-hand scoop technique to recap it. Dispose of the needle safely in a sharps container.

  • Sample Preparation
    Expel air bubbles from the syringe, cap it, and roll the specimen gently between your hands to mix it without compromising the sample’s integrity. Cap the syringe securely to prevent air contamination or leakage during transport.

  • Labeling and Transport
    Label the sample syringe appropriately and place it in a container with ice to preserve the sample. Transport it immediately to the laboratory, ensuring proper handling protocols are followed. Adhere to the recommended time frames for sample analysis to ensure accurate results:

    • For samples held at 4°C: Analysis should be conducted within 60 minutes.

    • For samples held at room temperature: Analysis should be conducted within 15 minutes.

  • Cleanup and Hygiene
    Dispose of all used materials and personal protective equipment in accordance with hospital protocols. Remove gloves and wash hands thoroughly with soap and water or use an alcohol-based hand rub.

  • Patient Reassessment
    Check the puncture site for ongoing bleeding or other complications. Apply additional pressure if necessary and thank the patient for their cooperation.

  • Special Considerations
    In critically ill or unresponsive patients, explain the procedure to family members or next of kin if possible. Additionally, minimize air bubbles in the sample as they can distort gas readings by altering PaO2 and PaCO2 levels.

  • Use of Local Anesthesia (Optional)
    Local anesthesia, such as lidocaine HCl 1% without epinephrine, may be administered subcutaneously to reduce discomfort [18, 19]. However, this step is not always necessary, as the pain from administering the anesthetic is often comparable to the pain of the procedure itself. If used, 0.5–1 mL of anesthetic should be injected to form a small dermal papule at the puncture site. Care should be taken not to distort the anatomy, and the clinician should aspirate before injection to confirm the needle is not inside a blood vessel.

Post Procedure Care and Recommendations

After completing the blood sampling procedure, appropriate post-procedure care is essential to ensure patient safety and minimize complications [16,17].

Closely monitor the patient for any new symptoms, such as changes in skin color, persistent or worsening pain, active bleeding, impaired limb movement, or altered sensation. Monitoring is particularly crucial for patients receiving anticoagulants or thrombolytic agents, as delayed re-bleeding can occur hours after the procedure.

Complications

The radial artery blood gas sampling procedure, although relatively safe, is associated with several potential complications. These complications and their preventive measures are detailed below [16]:

  1. Arteriospasm and Temporary Arterial Occlusion
    Arteriospasm can lead to temporary arterial occlusion, which may compromise blood flow to the affected limb. This can be prevented by helping the patient relax through clear explanations of the procedure, ensuring the patient is in a comfortable position, and using analgesia when necessary.

  2. Excessive Bleeding or Hematoma Formation
    Excessive bleeding or hematoma may cause compartment syndrome and subsequent limb ischemia. Prevention involves avoiding puncturing the far side of the artery, applying immediate and firm pressure at the puncture site for at least 3–5 minutes in non-anticoagulated patients, or 10–15 minutes for those on anticoagulants or with coagulopathy. Close monitoring is essential to ensure cessation of bleeding.

  3. Nerve Damage
    Nerve damage may occur during the procedure and can present as persistent pain or paresis. To minimize this risk, healthcare personnel should select an appropriate sampling site and avoid excessive redirection of the needle during the procedure.

  4. Vasovagal Response or Fainting Episodes
    A vasovagal response may lead to fainting or lightheadedness in some patients. This can be mitigated by ensuring the patient is in a supine position with their feet elevated.

  5. Infection at the Puncture Site or Needle-Stick Injuries
    Infection at the puncture site and needle-stick injuries pose risks to both patients and healthcare personnel. Strict adherence to infection prevention and control measures, such as using aseptic techniques and wearing appropriate personal protective equipment, is essential to prevent these complications.

  6. Air or Thrombus Embolism
    Air or thrombus embolism may occur if air bubbles are introduced during sampling or if an inappropriate syringe is used. This risk can be reduced by expelling air bubbles from the syringe and using a properly heparinized syringe during the procedure.

  7. Anaphylaxis from Local Anesthetic Agents
    Anaphylaxis may occur in response to local anesthetic agents. Taking a thorough patient history regarding previous allergic reactions or anaphylaxis is crucial before administering local anesthesia.

  8. Specific Concerns for Femoral Sampling
    In cases involving femoral artery sampling, be particularly cautious about bleeding complications. The larger caliber and deeper location of the femoral artery can allow significant blood accumulation without immediate clinical findings, increasing the risk of circulatory compromise.

  9. Other Notable Complications

    • Local Pain: May occur at the puncture site but can be minimized with proper technique and patient reassurance.
    • Vessel Laceration: Can result in profuse bleeding, requiring immediate evaluation and management.
    • Compartment Syndrome: A rapidly expanding hematoma may compromise regional circulation, necessitating prompt intervention. Symptoms include pain, paresthesias, pallor, absence of pulses, and persistent limb pain.
    • Limb Ischemia: Caused by arterial occlusion, thrombus formation, or vasospasm, it may present as absent distal pulses, coldness, and skin discoloration.

Hints and Pitfalls

To optimize the accuracy and success of radial ABG sampling while minimizing patient discomfort and complications, the following considerations should be observed [20]:

  1. Analgesia for Patient Comfort
    For patients experiencing anxiety or pain during the procedure, cryoanalgesia can be applied by placing an ice bag on the wrist for 3 minutes before arterial puncture. Alternatively, 0.5–1 mL of lignocaine 1% can be injected superficially to create a small wheal at the puncture site 30–60 seconds prior to sampling. Care should be taken to avoid deeper or larger volume injections, which may distort the anatomy and hinder vessel identification.

  2. Preventing Pre-Analytic Errors
    ABG measurements are highly sensitive to pre-analytic errors, including:

    • Presence of air in the sample, which can falsely elevate PaO2 and lower PaCO2.
    • Collection of venous rather than arterial blood.
    • Clotted samples due to improper anticoagulation, inadequate mixing, or exposure to air.
    • Delays in sample analysis exceeding 15 minutes at room temperature or 60 minutes at 4°C.

  3. Cooling Samples to Preserve Accuracy
    If analysis is expected to be delayed beyond 15 minutes, samples should be stored in a container with crushed ice to reduce metabolic activity of leukocytes and platelets. This prevents oxygen consumption and the associated clinically significant fall in PaO2, particularly in patients with leukocytosis or thrombocytosis.

  4. Impact of Air Bubbles
    Air bubbles introduced into the sample equilibrate with arterial blood, artificially increasing PaO2 toward 150 mmHg and decreasing PaCO2 toward 0 mmHg. Careful handling is essential to avoid air contamination.

  5. Use of Heparin as an Anticoagulant
    Heparin must be added to the syringe to prevent clotting. Flushing the syringe with heparin leaves an adequate amount in the dead space to ensure anticoagulation without affecting ABG results. Excess heparin should be expelled, as it can alter pH (falsely low) and gas measurements (falsely low PaO2 and PaCO2).

  6. Frequency of Sampling and Site Rotation
    The frequency of ABG sampling should be dictated by the patient’s clinical status. Repeated sampling at the same site increases the risk of hematoma, scarring, and arterial damage. Alternative sites should be used, or an indwelling catheter may be considered for patients requiring frequent sampling.

  7. Techniques for Unsuccessful Sampling
    Avoid pulling back the syringe plunger during unsuccessful attempts, as this increases the likelihood of venous sampling. Instead, withdraw the needle slowly until it is just beneath the skin and reattempt. Successful arterial sampling is indicated by the passive filling of the syringe with bright red, pulsating blood.

Special Patient Groups

Performing ABG sampling in pediatric patients presents unique challenges due to their fear, anxiety, and anticipation of pain, which may result in uncooperative behavior [20]. It is crucial to explain the procedure thoroughly to both the child and their parents before starting, ensuring informed consent is obtained. Allowing parents to be present during the procedure can provide comfort to the child, but healthcare providers should be mindful of the possibility that the parent may faint. In some cases, physical restraint of the child may be necessary to complete the procedure, although this approach could potentially traumatize the child. An alternative to percutaneous arterial sampling is capillary blood sampling from the heel, which can be used for gas analysis when arterial access is unavailable or when the clinician is less confident performing an arterial puncture.

For infants, arterial blood can be obtained from the radial, brachial, or dorsalis pedis arteries, while the umbilical arteries are an option in newborns. The radial artery remains the site of choice. In these patients, a small-gauge butterfly needle is preferred over the standard needle and syringe used in adults. Unlike adults, continuous but gentle suction should be applied during the procedure, and the appearance of pulsating blood is a reassuring sign that the radial artery has been successfully punctured.

In obese, edematous, or pregnant patients, the anatomical landmarks for arterial puncture may be difficult to identify. In such cases, the use of ultrasound guidance is highly beneficial for locating the artery. Ultrasound not only improves the success rate of arterial access but also reduces potential complications associated with repeated punctures, such as injury to the vessel or surrounding tissues.

Both pediatric and pregnant populations require special attention due to their unique anatomical and physiological considerations. In pediatrics, fear and discomfort associated with the procedure can make the hospital experience traumatic, emphasizing the need for proper explanation, comfort measures, and, when appropriate, pain-reducing products. In pregnant patients, the challenges often stem from anatomical changes caused by fluid retention or increased body mass.

Authors

Picture of Gan Kiat Kee

Gan Kiat Kee

Dr Gan Kiat Kee is an enthusiastic and passionate emergency physician from Hospital Sultanah Aminah Johor Bahru, Johor, Malaysia. He has obtained his medical degree from University Sains Malaysia and completed his post-graduate training in emergency medicine from the same university. He has special interest in acute trauma care and ultrasound guided procedures especially in ultrasound guided regional anaesthesia for pain management in trauma patient. He is also the founder for Emergency Department Regional Anaesthesia (EDRA) of his current working department. Owing to his great interest in simulation and bedside teaching, he has been appointed as adjunct lecturer by Clinical School Johor Bahru, Monash University Malaysia and has been active in teaching various life support.

Picture of Arif Alper Cevik, MD, FEMAT, FIFEM

Arif Alper Cevik, MD, FEMAT, FIFEM

Prof Cevik is an Emergency Medicine academician at United Arab Emirates University, interested in international emergency medicine, emergency medicine education, medical education, point of care ultrasound and trauma. He is the founder and director of the International Emergency Medicine Education Project – iem-student.org, chair of the International Federation for Emergency Medicine (IFEM) core curriculum and education committee and board member of the Asian Society for Emergency Medicine and Emirati Board of Emergency Medicine.

Listen to the chapter

References

  1. Hassan W, Martinez S. Arterial Blood Gas Sampling [ABG Machine Use]. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024. Updated May 9, 2024. Accessed January 1, 2025. https://www.ncbi.nlm.nih.gov/books/NBK606112/
  2. Danckers M. Arterial blood sampling for arterial blood gas analysis. Medscape. Updated February 29, 2024. Accessed January 1, 2025. https://emedicine.medscape.com/article/1902703-overview
  3. Castro D, Patil SM, Zubair M, Keenaghan M. Arterial Blood Gas. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024. Updated January 8, 2024.
  4. Kitamura BC, Sarko J. Arterial Blood Gas. In: Sherman SC, Weber JM, Schindlbeck MA, et al., eds. Clinical Emergency Medicine. New York, NY: McGraw-Hill Education; 2014. Accessed January 1, 2025. https://accessemergencymedicine.mhmedical.com/content.aspx?bookid=991&sectionid=57306093
  5. Rowe BH, Bhutani M, Stickland MK, Cydulka R. Assessment and management of chronic obstructive pulmonary disease in the emergency department and beyond. Expert Rev Respir Med. 2011;5(4):549-559.
  6. Arena A, Miller E. Respiratory acid-base disorders. Emerg Med Clin North Am. 2023;41(4):863-875. doi:10.1016/j.emc.2023.06.009
  7. Rose JJ, Wang L, Xu Q, et al. Carbon monoxide poisoning: pathogenesis, management, and future directions of therapy. Am J Respir Crit Care Med. 2017;195(5):596-606. doi:10.1164/rccm.201606-1275CI
  8. American Association for Respiratory Care. AARC clinical practice guideline: sampling for arterial blood gas analysis. Respir Care. 1992;37(8):891-897.
  9. Theodore AC. Venous blood gases and other alternatives to arterial blood gases. In: Manaker S, Finlay G, eds. UpToDate. Waltham, MA: UpToDate; 2021. Accessed February 2, 2021. https://www.uptodate.com/contents/venous-blood-gases-and-other-alternatives-to-arterial-blood-gases
  10. Dev SP, Hillmer MD, Ferri M. Arterial puncture for blood gas analysis. N Engl J Med. 2011;364(5):e7.
  11. Liang SY, Theodoro DL, Schuur JD, Marschall J. Infection prevention in the emergency department. Ann Emerg Med. 2014;64(3):299-313. doi:10.1016/j.annemergmed.2014.02.024
  12. Gerhard-Herman MD, Gornik HL, Barrett C, et al. 2016 AHA/ACC guideline on the management of patients with lower extremity peripheral artery disease: executive summary. Circulation. 2017;135(12):e686-e725. doi:10.1161/CIR.0000000000000470
  13. Sony S, Shekhar S, Walikar BN, Shiwali S. Raynaud’s phenomenon during non-operating room anesthesia: a case report. Cureus. 2022;14(12):e32906. doi:10.7759/cureus.32906
  14. Satiani B, Sowden DT. Hand ischemia. J Fam Pract. 1982;15(1):163-169.
  15. Rowling SC, Fløjstrup M, Henriksen DP, et al. Arterial blood gas analysis: as safe as we think? A multicentre historical cohort study. ERJ Open Res. 2022;8(1):00535-2021. doi:10.1183/23120541.00535-2021
  16. Danckers M, Fried ED. Arterial blood sampling for arterial blood gas analysis. Medscape. Updated February 29, 2024. Accessed January 4, 2025. https://emedicine.medscape.com/article/1902703-overview
  17. World Health Organization. WHO guidelines on drawing blood: best practices in phlebotomy. Geneva: World Health Organization; 2010. Accessed January 4, 2025. https://www.ncbi.nlm.nih.gov/books/NBK138661/
  18. Lightowler JV, Elliott MW. Local anaesthetic infiltration prior to arterial puncture for blood gas analysis: a survey of current practice and a randomised double blind placebo controlled trial. J R Coll Physicians Lond. 1997;31(6):645-648.
  19. Pagnucci N, Pagliaro S, Maccheroni C, et al. Reducing pain during emergency arterial sampling using three anesthetic methods: a randomized controlled clinical trial. J Emerg Med. 2020;58(6):857-864.
  20. Ambroz M, Prosen G. Arterial blood gas (ABG) sampling. International Emergency Medicine Education Project. Accessed January 4, 2025. https://iem-student.org/arterial-blood-gas-abg-sampling/

Reviewed and Edited By

Picture of Arif Alper Cevik, MD, FEMAT, FIFEM

Arif Alper Cevik, MD, FEMAT, FIFEM

Prof Cevik is an Emergency Medicine academician at United Arab Emirates University, interested in international emergency medicine, emergency medicine education, medical education, point of care ultrasound and trauma. He is the founder and director of the International Emergency Medicine Education Project – iem-student.org, chair of the International Federation for Emergency Medicine (IFEM) core curriculum and education committee and board member of the Asian Society for Emergency Medicine and Emirati Board of Emergency Medicine.

Question Of The Day #15

question of the day
~ Joseph Ciano, USA ~ Leave a comment
qod 15 - pleuritic chest pain

Which of the following is the best course of action to further evaluate for a diagnosis of pulmonary embolism?

  • A) Perform a V/Q scan
  • B) Draw a D-Dimer test
  • C) Perform a CT Pulmonary Angiogram
  • D) Give lorazepam
Pulmonary embolism (PE) is a potentially lethal diagnosis evaluated by a combination of a thorough history, physical exam, and the use of risk stratification scoring tools. The Wells criteria and the PE rule-out criteria (PERC) are two well-accepted risk stratification tools for PE. These criteria are each listed below (Wieters et al., 2020).

Wells’ Criteria for Pulmonary Embolism

CriteriaPoint Value
Clinical signs and symptoms of DVT+3
PE is #1 diagnosis, or equally likely+3
Heart rate > 100+1.5
Immobilization at least 3 days, or Surgery in the Previous 4 weeks+1.5
Previous, objectively diagnosed PE or DVT+1.5
Hemoptysis+1
Malignancy w/ Treatment within 6 mo, or palliative+1
Interpretation
Score >4 = High probability
Score 2–4 = Moderate probability
Score <2 = Low probability

Pulmonary Embolism Rule Out Criteria

All Variables Must Be Present for <2% Chance of PE
Pulse oximetry >94% (room air)
HR <100
No prior PE or DVT
No recent surgery or trauma within prior 4 wk
No hemoptysis
No estrogen use
No unilateral leg swelling
The patient in this clinical vignette would have a Wells score of 1.5 (low risk) due to her persistent tachycardia of unknown etiology. The PERC rule can not be applied to this patient as she is over 50-years-old and has tachycardia. If the patient was low risk on Wells score and meet all the PERC rule criteria, she would have a less than 2% likelihood of her symptoms being due to a PE. It is important to note that only patients with a low-risk Wells score (low pretest probability for PE) can be subjected to the PERC rule. A low-risk Wells score (<2) is investigated with a D-Dimer test (Choice B), while moderate to high-risk Wells scores are investigated with a CT Pulmonary Angiogram (CTPA) (Choice C). A V/Q Scan (Choice A) is not a first-line test for the diagnosis of PE as it is less sensitive than a CTPA scan. Unlike a CTPA scan, a V/Q scan may be nondiagnostic in the setting of lung consolidation, effusions, or other airspace diseases. V/Q scans are second-line tests to CTPA when there are contraindications to a CTPA (i.e., renal failure). Lorazepam (Choice D) is a benzodiazepine that may be helpful in reducing tachycardia, which is secondary to anxiety. However, this therapy does not help further discern if the patient may have a PE. Correct Answer: B 

References

Wieters J, McDonough J, Catral J. Chest Pain. In: Stone C, Humphries RL. eds. CURRENT Diagnosis & Treatment: Emergency Medicine, 8e. McGraw-Hill; Accessed August 17, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=2172&sectionid=165059275

Nickson, C. (2019). Pulmonary Embolism. Life in the Fastlane. Accessed on August 17, 2020. https://litfl.com/pulmonary-embolism/

[cite]

You may want to read these

Pulmonary Embolism – https://iem-student.org/pulmonary-embolism/

Clinical Decision Rules – https://iem-student.org/clinical-decision-rules/

Question of The Day #6 – https://iem-student.org/2020/07/31/question-of-the-day-6/

Hypokalemic Periodic Paralysis in the ED

Hypokalemic Periodic Paralysis in the ED
~ Sumaiya Hafiz, UAE ~ 1 Comment

Case Presentation

A middle-aged man with a two days history of weakness in his legs. The patient works as a construction worker and is used to conducting heavy physical activity.

After a thorough history and examination, the weakness was reported in the lower extremities with a power of 2/5, whereas the power in upper extremities was 4.5/5, Achilles tendon reflex was reduced, plantar response and other reflexes were intact, with normal sensation. Rest of the examination is unremarkable.

The vitals are within normal ranges, Blood investigations include – Urea and electrolytes, liver and renal function, full blood count, thyroid function tests, creatine kinase, urine myoglobin, vitamin B12 and folic acid levels.

Potassium level was 1.7 mEq/L (normal 3.5-5.5), and all other parameters were within normal ranges.

The ECG showed inverted T waves and the presence of U waves. An Example of an ECG:

ECG-hypokalemia

Hypokalaemia

Hypokalemic periodic paralysis is a rare disorder that may be hereditary as the primary cause, or secondary due to thyroid disease, strenuous physical activity, a carbohydrate-rich meal and toxins. The patients are mostly of Asian origin.

The most common presentation is of symmetrical weakness in lower limbs, with a low potassium level and ECG changes of hypokalemia. The patients may have a history of similar weaknesses which may be several years old. An attack may be triggered by infections, stress, exercise and other stress-related factors.

The word ‘weakness’, can lead to physicians thinking about stroke, neurological deficits and other life-threatening illnesses such as spinal cord injuries associated with high morbidity and mortality which need to be ruled out in the ED.

In this case, history and examination are vital. Weakness in other parts of the body, a thorough neurological examination are important aspects.

Patients are monitored and treated with potassium supplements (oral/Intravenous) until the levels normalize. ECG monitoring is essential, as cardiac function may be affected. 

The patient should be examined to assess the strength and should be referred for further evaluation and to confirm the diagnosis.

The differential diagnosis for weakness in lower limb include :

  1. Spinal cord disease (https://iem-student.org/spine-injuries/)
  2. Guillain barre syndrome
  3. Toxic myositis
  4. Trauma
  5. Neuropathy
  6. Spinal cord tumour

References

[cite]

Troponin and nothing more

troponin and nothin more
~ Israa M Salih, UAE ~ Leave a comment

It’s almost impossible to have an ER shift without encountering a chest pain patient!

The first thing that always comes to mind is to rule out STEMI; well, unless the patient is having chest pain, and you see a knife stabbed in his chest!

It’s a no brainer situation; investigations wise, you will start with an EKG, and a set of labs, including cardiac markers.

Acute coronary syndrome (ACS) with its subcategories, ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), and unstable angina, is responsible for one third of total mortality in individuals more than 35 years of age.(1)

The role of cardiac markers in diagnosis and management of ACS and cardiovascular problems is vital. In the United States cardiac biomarkers testing occurs in nearly 30 million emergency department visits nationwide each year.(2)

What is a biomarker?

The National Institutes of Health defined a biomarker as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.” (3)

Biomarkers utilization in cardiovascular medicine is a wide domain; it’s used in screening, diagnosis, prognosis and monitoring. (4)

What’s available?

Numerous cardiac markers are available today and can be classified as:

  1. Biomarkers of myocardial injury, which is further divided into:
    1. Biomarkers of myocardial necrosis: CK-MB fraction, myoglobin, cardiac troponins
    2. Biomarkers of myocardial ischemia: Ischemia-modified albumin (IMA), heart-type fatty acid-binding protein (H-FABP)
  2. Biomarkers of hemodynamic stress: Natriuretic peptides (NPs): atrial natriuretic peptide (ANP), N-terminal proBNP (NT-proBNP), B-type natriuretic peptide (BNP)
  3. Inflammatory and prognostic markers: hs C-reactive protein (CRP), sCD40L, homocysteine. (4)

What’s best?

Cardiac Troponin and the B type cardiac natriuretic peptides are the two markers recommended by ACEP and AHA in diagnosis of ACS and heart failure respectively.(5)

The ACS biomarker of choice

ACS is subcategorized based on ECG and cardiac troponin. The fourth universal consensus definition of Myocardial Infarction (MI); by the European Society of Cardiology (ESC) and American College of Cardiology (ACC), takes Troponin as a detrimental parameter in case definition, because of its high sensitivity and specificity.(6)

ACEP and AHA guidelines recommend the use of Troponin as level A class 1 in diagnosis of ACS. (7) It was practiced before to consider multiple markers dealing with ACS, more precisely in NSTEMI ruling out recommendation. However, this practice is now outdated with the use of hs cT solely.(7-9)

What’s troponin and why do we like it?

It’s a protein that regulates the interaction between actin and myosin filaments, found in skeletal and cardiac myocytes. Cardiac troponin (cTn) has three subunits troponin T, troponin C and troponin I. Troponin T and I are highly specific and sensitive.(10) The half-life of troponin T and troponin I in the blood is about 2 hours and last in serum for 4 to 10 days10

For ACS, the sensitivity of troponin is about 95%, and the specificity is about 80%, higher than any other marker available.(12)

However, many causes can elevate serum troponin which includes pericarditis, myocarditis, heart failure and chest trauma; non-cardiac conditions are sepsis, renal disease, pulmonary embolism, COPD, strenuous exercise and hypertension.(14)

High-sensitivity cardiac troponin (hs-cTn T and I) can detect troponin at concentrations much lower than the old cTn tests, and has replaced it.7 For ACS, hs cT substituted and limited the roles of other markers; it’s proven to be safe, cost effective, and a valuable prognostic factor. (7-9, 14)

For all of the above and the heart score… In ACS, use Troponin and nothing more!

References and Further Reading

  1. Anumeha Singh; Abdulrahman S. Museedi; Shamai A. Grossman. Acute Coronary Syndrome. StatPearls[Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan.
  2. Alvin MD, Jaffe AS, Ziegelstein RC, Trost JC. Eliminating Creatine Kinase–Myocardial Band Testing in Suspected Acute Coronary Syndrome: A Value-Based Quality Improvement. JAMA Intern Med. 2017;177(10):1508-1512. doi:10.1001/jamainternmed.2017.3597.
  3. Biomarkers and surrogate endpoints: preferred definitions and conceptual framework. Biomarkers Definitions Working Group. Clin Pharmacol Ther. 2001 Mar; 69(3):89-95. doi.org/10.1067/mcp.2001.113989.
  4. Jacob R, Khan M. Cardiac Biomarkers: What Is and What Can Be. Indian J Cardiovasc Dis Women WINCARS. 2018 Dec; 3(4): 240–244. doi: 10.1055/s-0039-1679104.
  5. Richards AM. Future biomarkers in cardiology: My favourites. European Heart Journal Supplements, Volume 20, Issue suppl_ G, 1 August 2018, Pages G37-G44. doi.org/10.1093/eurheartj/suy023.
  6. Thygesen K, Alpert JS, Jaffe AS, et al., on behalf of the Joint European Society of Cardiology (ESC)/American College of Cardiology (ACC)/American Heart Association (AHA)/World Heart Federation (WHF) Task Force for the Universal Definition of Myocardial Infarction. Fourth Universal Definition of Myocardial Infarction (2018). J Am Coll Cardiol. 2018. Volume 72 DOI: 10.1016/j.jacc.2018.08.1038. 
  7. Ezra A. Amsterdam, Nanette K Wenger, Ralph G. Brindis, Donald E. CaseyJr, Theodore G. Ganiats, David. HolmesJr, Allan S. Jaffe, Hani Jneid, Rosemary F. Kelly, Michael C. Kontos, Glenn N. Levine, Philip R. Liebson,Debabrata Mukherjee, Eric D. Peterson, Marc S. Sabatine, Richard W. Smalling, Susan J. Zieman. 2014 AHA/ACC Guideline for the Management of Patients With Non–ST-Elevation Acute Coronary Syndromes: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014; 130:e344–e426. 2014. doi.org/10.1161/CIR.0000000000000134.
  8. Edward W Carlton, Louise Cullen, Martin Than, James Gamble, Ahmed Khattab, Kim Greaves. A novel diagnostic protocol to identify patients suitable for discharge after a single high-sensitivity troponin. Heart. 2015 Jul 1; 101(13): 1041–1046. doi: 10.1136/heartjnl-2014-307288.
  9. Ron M. Walls, Robert S. Hockberger, Marianne Gausche-Hill, Katherine Bakes, Jill Marjorie Baren, Timothy B. Erickson, Andy S. Jagoda, Amy H. Kaji, Michael VanRooyen, Richard D. Zane. Rosen’s Emergency Medicine: Concepts and clinical practice. 9th edition. Elseivier; 2018.
  10. Ooi DS1, Isotalo PA, Veinot JP. Correlation of antemortem serum creatine kinase, creatine kinase-MB, troponin I, and troponin T with cardiac pathology. Clin Chem. 2000 Mar; 46(3):338-44.
  11. Harvey D. White, DSC. Pathobiology of Troponin Elevations: Do Elevations Occur With Myocardial Ischemia as Well as Necrosis?. Journal of the American College of Cardiology. Vol. 57, No. 24, ISSN 0735-1097/$36.00 Published by Elsevier Inc. doi:10.1016/j.jacc.2011.01.029.
  12. John E. Brush, Jr., Harlan M. Krumholz. A Brief Review of Troponin Testing for Clinicians. American College of Cardiology. 2017 Aug 7th. acc.org/latest-in-cardiology/articles/2017/08/07/07/46/a-brief-review-of-troponin-testing-for-clinicians.
  13. Asli Tanindi, Mustafa Cemri. Troponin elevation in conditions other than acute coronary syndromes. Vasc Health Risk Manag. 2011; 7: 597–603. PMID: 22102783. doi: 10.2147/VHRM.S24509.
  14. Donald Schreiber, Barry E Brenner. Cardiac Markers. emedicine.medscape.com/article/811905-overview [Accessed 2020 March 23rd].
[cite]