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Table of Contents

Abbreviations 1292

• 1.
  

  Introduction 1291

  
  
• 2.
  

  Methodology and Evidence Review 1292

  
  
• 3.
  

  Ultrasound-Guided Vascular Cannulation 1292

  
  
• 4.
  

  Ultrasound Principles for Needle-Guided Catheter Placement 1292

  
  
• 5.
  

  Real-Time Imaging Versus Static Imaging 1294

  
  
• 6.
  

  Vessel Identification 1297

  
  
• 7.
  

  Internal Jugular Vein Cannulation 1297

  
  
  
  
  • 7.1.
    

    Anatomic Considerations 1297

    
    
  • 7.2.
    

    Cannulation Technique 1298

    
    
  • 7.3.
    

    Complications 1298

    
    
  • 7.4.
    

    Recommendation for IJ Vein Cannulation 1300

  
  
  
  
• 8.
  

  Subclavian Vein Cannulation 1300

  
  
  
  
  • 8.1.
    

    Anatomic Considerations 1300

    
    
  • 8.2.
    

    Cannulation Technique 1300

    
    
  • 8.3.
    

    Complications 1301

    
    
  • 8.4.
    

    Recommendation for SC Vein Cannulation 1302

  
  
  
  
• 9.
  

  Femoral Vein Cannulation 1302

  
  
  
  
  • 9.1.
    

    Anatomic Considerations 1302

    
    
  • 9.2.
    

    Cannulation Technique 1302

    
    
  • 9.3.
    

    Complications 1303

    
    
  • 9.4.
    

    Recommendation for FV Cannulation 1303

  
  
  
  
• 10.
  

  Pediatric Ultrasound Guidance 1303

  
  
  
  
  • 10.1.
    

    Cannulation Technique 1304

    
    
    
    
    • 10.1.1.
      

      IJ Vein 1304

      
      
    • 10.1.2.
      

      Femoral Vessels 1304

    
    
    
    
  • 10.2.
    

    Recommendations for Pediatric Patients 1305

  
  
  
  
• 11.
  

  Ultrasound-Guided Arterial Cannulation 1305

  
  
  
  
  • 11.1.
    

    Cannulation Technique 1306

    
    
  • 11.2.
    

    Ultrasound-Guided Arterial Cannulation Versus Palpation 1307

    
    
  • 11.3.
    

    Recommendation for Arterial Vascular Access 1307

  
  
  
  
• 12.
  

  Ultrasound-Guided Peripheral Venous Cannulation 1307

  
  
  
  
  • 12.1.
    

    Recommendation for Peripheral Venous Access 1308

  
  
  
  
• 13.
  

  Vessel Selection 1308

  
  
• 14.
  

  Vascular Access Confirmation 1308

  
  
  
  
  • 14.1.
    

    Recommendations for Vascular Access Confirmation 1308

  
  
  
  
• 15.
  

  Training 1308

  
  
• 16.
  

  Conclusions 1309

  
  
• 
  

  Notice and Disclaimer 1309

  
  
• 
  

  References 1309

  
  
• 
  

  Appendix A 1312

  
  
• 
  

  Appendix B 1313

Table of Contents

Abbreviations 1292

• 1.
  

  Introduction 1291

  
  
• 2.
  

  Methodology and Evidence Review 1292

  
  
• 3.
  

  Ultrasound-Guided Vascular Cannulation 1292

  
  
• 4.
  

  Ultrasound Principles for Needle-Guided Catheter Placement 1292

  
  
• 5.
  

  Real-Time Imaging Versus Static Imaging 1294

  
  
• 6.
  

  Vessel Identification 1297

  
  
• 7.
  

  Internal Jugular Vein Cannulation 1297

  
  
  
  
  • 7.1.
    

    Anatomic Considerations 1297

    
    
  • 7.2.
    

    Cannulation Technique 1298

    
    
  • 7.3.
    

    Complications 1298

    
    
  • 7.4.
    

    Recommendation for IJ Vein Cannulation 1300

  
  
  
  
• 8.
  

  Subclavian Vein Cannulation 1300

  
  
  
  
  • 8.1.
    

    Anatomic Considerations 1300

    
    
  • 8.2.
    

    Cannulation Technique 1300

    
    
  • 8.3.
    

    Complications 1301

    
    
  • 8.4.
    

    Recommendation for SC Vein Cannulation 1302

  
  
  
  
• 9.
  

  Femoral Vein Cannulation 1302

  
  
  
  
  • 9.1.
    

    Anatomic Considerations 1302

    
    
  • 9.2.
    

    Cannulation Technique 1302

    
    
  • 9.3.
    

    Complications 1303

    
    
  • 9.4.
    

    Recommendation for FV Cannulation 1303

  
  
  
  
• 10.
  

  Pediatric Ultrasound Guidance 1303

  
  
  
  
  • 10.1.
    

    Cannulation Technique 1304

    
    
    
    
    • 10.1.1.
      

      IJ Vein 1304

      
      
    • 10.1.2.
      

      Femoral Vessels 1304

    
    
    
    
  • 10.2.
    

    Recommendations for Pediatric Patients 1305

  
  
  
  
• 11.
  

  Ultrasound-Guided Arterial Cannulation 1305

  
  
  
  
  • 11.1.
    

    Cannulation Technique 1306

    
    
  • 11.2.
    

    Ultrasound-Guided Arterial Cannulation Versus Palpation 1307

    
    
  • 11.3.
    

    Recommendation for Arterial Vascular Access 1307

  
  
  
  
• 12.
  

  Ultrasound-Guided Peripheral Venous Cannulation 1307

  
  
  
  
  • 12.1.
    

    Recommendation for Peripheral Venous Access 1308

  
  
  
  
• 13.
  

  Vessel Selection 1308

  
  
• 14.
  

  Vascular Access Confirmation 1308

  
  
  
  
  • 14.1.
    

    Recommendations for Vascular Access Confirmation 1308

  
  
  
  
• 15.
  

  Training 1308

  
  
• 16.
  

  Conclusions 1309

  
  
• 
  

  Notice and Disclaimer 1309

  
  
• 
  

  References 1309

  
  
• 
  

  Appendix A 1312

  
  
• 
  

  Appendix B 1313

1. Introduction

The Agency for Healthcare Research and Quality, in its 2001 report Making Health Care Safer: A Critical Analysis of Patient Safety Practices , recommended the use of ultrasound for the placement of all central venous catheters as one of its 11 practices aimed at improving patient care. The purpose of this document is to provide comprehensive practice guidelines on the use of ultrasound for vascular cannulation. Recommendations are made for ultrasound-guided central venous access of the internal jugular (IJ) vein, subclavian (SC) vein, and femoral vein (FV) on the basis of the strength of the scientific evidence present in the literature ( Table 1 ). The role of ultrasound for vascular cannulation of pediatric patients is discussed specifically, and the use of ultrasound to facilitate arterial cannulation and peripheral venous access is also discussed. Recommendations are made for training, including the role of simulation.

2. Methodology and Evidence Review

The writing committee conducted a comprehensive search of medical and scientific literature in the English language through the use of PubMed and MEDLINE. Original research studies relevant to ultrasound-guided vascular access published in peer-reviewed scientific journals from 1990 to 2011 were reviewed using the Medical Subject Headings terms “ultrasonography,” “catheterization-central venous/adverse effects/methods,” “catheterization-peripheral,” “jugular veins,” “subclavian vein,” “femoral vein,” “artery,” “adult,” “pediatric,” “randomized controlled trials,” and “meta-analysis.” The committee reviewed the scientific evidence for the strength of the recommendation (i.e., risk/benefit ratio) as supportive evidence (category A), suggestive evidence (category B), equivocal evidence (category C), or insufficient evidence (category D). The weight or “level” of evidence was assigned within each category ( Table 1 ). Recommendations for the use of ultrasound were based on supportive literature (category A) with a level 1 weight of scientific evidence (multiple randomized controlled trials with the aggregated findings supported by meta-analysis). The document was reviewed by 10 reviewers nominated by the American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists and approved for publication by the governing bodies of these organizations.

3. Ultrasound-Guided Vascular Cannulation

Ultrasonography was introduced into clinical practice in the early 1970s and is currently used for a variety of clinical indications. Miniaturization and advancements in computer technology have made ultrasound affordable, portable, and capable of high-resolution imaging of both tissue and blood flow.

Cannulation of veins and arteries is an important aspect of patient care for the administration of fluids and medications and for monitoring purposes. The practice of using surface anatomy and palpation to identify target vessels before cannulation attempts (“landmark technique”) is based on the presumed location of the vessel, the identification of surface or skin anatomic landmarks, and blind insertion of the needle until blood is aspirated. Confirmation of successful cannulation of the intended vascular structure relies on blood aspiration of a certain character and color (i.e., the lack of pulsation and “dark” color when cannulating a vein or pulsation and a “bright” red color when cannulating an artery), pressure measurement with a fluid column or pressure transducer, or observation of the intraluminal pressure waveform on a monitor. Although vascular catheters are commonly inserted over a wire or metal introducer, some clinicians initially cannulate the vessel with a small caliber (“finder”) needle before the insertion of a larger bore needle. This technique is most beneficial for nonultrasound techniques, because a smaller needle may minimize the magnitude of an unintended injury to surrounding structures. The vessel is then cannulated with a larger bore 16-gauge or 18-gauge catheter, a guide wire is passed through it, and a larger catheter is inserted over the wire. The catheter–over–guide wire process is termed the Seldinger technique.

Although frequently performed and an inherent part of medical training and practice, the insertion of vascular catheters is associated with complications. Depending on the site and patient population, landmark techniques for vascular cannulation are associated with a 60% to 95% success rate. A 2003 estimate cited the insertion of >5 million central venous catheters (in the IJ, SC, and FV) annually in the United States alone, with a mechanical complication rate of 5% to 19%. These complications may occur more often with less experienced operators, challenging patient anatomy (obesity, cachexia, distorted, tortuous or thrombosed vascular anatomy, congenital anomalies such as persistent left superior vena cava), compromised procedural settings (mechanical ventilation or emergency), and the presence of comorbidity (coagulopathy, emphysema). Central venous catheter mechanical complications include arterial puncture, hematoma, hemothorax, pneumothorax, arterial-venous fistula, venous air embolism, nerve injury, thoracic duct injury (left side only), intraluminal dissection, and puncture of the aorta. The most common complications of IJ vein cannulation are arterial puncture and hematoma. The most common complication of SC vein cannulation is pneumothorax. The incidence of mechanical complications increases sixfold when more than three attempts are made by the same operator. The use of ultrasound imaging before or during vascular cannulation greatly improves first-pass success and reduces complications. Practice recommendations for the use of ultrasound for vascular cannulation have emerged from numerous specialties, governmental agencies such as the National Institute for Health and Clinical Excellence and the Agency for Healthcare Research and Quality’s evidence report.

4. Ultrasound Principles for Needle-Guided Catheter Placement

Ultrasound modalities used for imaging vascular structures and surrounding anatomy include two-dimensional (2D) ultrasound, Doppler color flow, and spectral Doppler interrogation. The operator must have an understanding of probe orientation, image display, the physics of ultrasound, and mechanisms of image generation and artifacts and be able to interpret 2D images of vascular lumens of interest and surrounding structures. The technique also requires the acquisition of the necessary hand-eye coordination to direct probe and needle manipulation according to the image display. The supplemental use of color flow Doppler to confirm presence and direction of blood flow requires an understanding of the mechanisms and limitations of Doppler color flow analysis and display. This skill set must then be paired with manual dexterity to perform the three-dimensional (3D) task of placing a catheter into the target vessel while using and interpreting 2D images. Two-dimensional images commonly display either the short axis (SAX) or long axis (LAX) of the target vessel, each with its advantage or disadvantage in terms of directing the cannulating needle at the correct entry angle and depth. Three-dimensional ultrasound may circumvent the spatial limitations of 2D imaging by providing simultaneous real-time SAX and LAX views along with volume perspective without altering transducer location, allowing simultaneous views of neck anatomy in three orthogonal planes. Detailed knowledge of vascular anatomy in the region of interest is similarly vital to both achieving success and avoiding complications from cannulation of incorrect vessels.

Ultrasound probes used for vascular access vary in size and shape. Probes with smaller footprints are preferred in pediatric patients. Higher frequency probes (≥7 MHz) are preferred over lower frequency probes (<5 MHz) because they provide better resolution of superficial structures in close proximity to the skin surface. The poorer penetration of the high-frequency probes is not typically a hindrance, because most target vascular structures intended for cannulation are <8 to 10 cm from the skin surface.

It is important to appreciate how probe orientation relates to the image display. Conventions established by the ASE for performing transthoracic imaging of the heart, and more recently epicardial imaging, established that the probe indicator and right side of the display should be oriented toward the patient’s left side or cephalad. In these settings, projected images correlate best with those visualized by the sonographer positioned on the patient’s left side and facing the patient’s right shoulder. In contrast, the operator’s position during ultrasound-guided vascular access varies according to the target vessel. For example, the operator is typically positioned superior to the patient’s head and faces caudally during cannulation of the IJ vein. The left side of the screen displays structures toward the patient’s left side ( Figure 1 ). In contrast, during cannulation of the FVs, the operator is typically positioned inferiorly and faces cephalad, so that the left side of the screen displays structures toward the patient’s right side (see section 9 , “Femoral Vein Cannulation”). For SC vein cannulation, the left and right sides of the screen display cephalad and caudad structures, depending on laterality (right or left). The changing image orientation is an important distinction from typical transthoracic, epicardial, or transesophageal imaging. For ultrasound-guided vascular access cannulation, the probe and screen display are best oriented to display the anatomic cross-section that would be visible from the same vantage point. Therefore, screen left and right will not follow standard conventions but rather vary with site and needle insertion orientation. What is common for all vascular access sites is that it is essential for the operator to orient the probe so that structures beneath the left aspect of the probe appear on the left side of the imaging screen. Although probes usually have markings that distinguishes one particular side of the transducer, the operator must identify which aspect of the screen corresponds to the marking on the probe. These markings may be obscure, and a recommended practice is to move the probe toward one direction or another while observing the screen or apply modest external surface pressure on one side of the transducer to demonstrate proper alignment of left-right probe orientation with image display.

Right neck central vein cannulation. The ultrasound probe is held so that each side of the screen displays ipsilateral structures. With the probe mark placed on the upper left corner of the image, the displayed structures will move in the same direction with the probe.

The probe used ultimately depends on its availability, operator experience, ease of use, and patient characteristics (e.g., smaller patients benefit from smaller probes). Some probes allow the use of a needle guide, which directs the needle into the imaging plane and defined depth as viewed on the display screen ( Figure 2 ). Needle guides are not available from every ultrasound probe manufacturer, but a needle guide may be a useful feature for the beginner who has not yet developed the manual dexterity of using a 2D image display to perform a 3D task. One study that evaluated ultrasound-guided cannulation of the IJ vein with and without a needle guide showed that its use significantly enhanced cannulation success after first (68.9%–80.9%, P = .0054) and second (80.0%–93.1%, P = .0001) needle passes. Cumulative cannulation success after seven needle passes was 100%, regardless of technique. The needle guide specifically improved first-pass success among more junior operators (65.6%–79.8%, P = .0144), while arterial puncture averaged 4.2%, regardless of technique ( P > .05) or operator ( P > .05). A limitation of the needle guide is that the needle trajectory is limited to orthogonal orientations from the SAX imaging plane. Although helpful in limiting lateral diversion of the needle path, sometimes oblique angulation of the needle path may facilitate target vessel cannulation. In addition, there may be considerable costs associated with the use of needle guides. Depending on the manufacturer, they may cost as little as several dollars to >$100 each. Importantly, although the needle guide facilitated prompt cannulation with ultrasound in the novice operator, it offered no additional protection against arterial puncture. However, one in vitro simulation study has refuted these in vivo results.

Various needle guides, used to direct the needle at the center of the probe (and image) and at an appropriate angle and depth beneath the probe. IJV , IJ vein.

From Troianos CA. Intraoperative monitoring. In: Troianos CA, ed. Anesthesia for the Cardiac Patient. New York: Mosby; 2002.

Arterial puncture during attempted venous cannulation with ultrasound generally occurs because of a misalignment between the needle and imaging screen. It may also occur as a result of a through-and-through puncture of the vein into a posteriorly positioned artery. The first scenario is due to improper direction of the needle, while the latter occurs because of a lack of needle depth control. Needle depth control is also an important consideration because the anatomy may change as the needle is advanced deeper within the site of vascular access. The ideal probe should have a guide that not only directs the needle to the center of the probe but also directs the needle at the appropriate angle beneath the probe ( Figure 2 ). This type of guide compensates for the limitation of using 2D ultrasound to perform a 3D task of vascular access. The more experienced operator with a better understanding of these principles and better manual dexterity may find the needle guide cumbersome, choosing instead the “maneuverability” of a freehand technique. Although the routine use of a needle guide requires further study, novice operators are more likely to improve their first-pass success.

Vascular structures can be imaged in SAX, LAX, or oblique orientation ( Figures 3 A, 3B, and 3C). The advantage of the SAX view is better visualization of surrounding structures and their relative positions to the needle. There is usually an artery in close anatomic proximity to most central veins. Identification of both vascular structures is paramount to avoid unintentional cannulation of the artery. In addition, it may be easier to direct the cannulating needle toward the target vessel and coincidentally away from surrounding structures when both are clearly imaged simultaneously. The advantage of the LAX view is better visualization of the needle throughout its course and depth of insertion, because more of the needle shaft and tip are imaged within the ultrasound image plane throughout its advancement, thereby avoiding insertion of the needle beyond the target vessel. A prospective, randomized observational study of emergency medicine residents evaluated whether the SAX or LAX ultrasound approach resulted in faster vascular access for novice ultrasound users. The SAX approach yielded a faster cannulation time compared with the LAX approach, and the novice operators perceived the SAX approach as easier to use than the LAX approach. The operator’s hand-eye coordination skill in aligning the ultrasound probe and needle is probably the most important variable influencing needle and target visibility. Imaging in the SAX view enables the simultaneous visualization of the needle shaft and adjacent structures, but this view does not image the entire needle pathway or provide an appreciation of insertion depth. Although novice users may find ultrasound guidance easier to adopt using SAX imaging, ultrasound guidance with LAX imaging should be promoted, because it enables visualization of the entire needle and depth of insertion, thereby considering anatomic variations along the needle trajectory as the needle is advanced deeper within the site of vascular access. The oblique axis is another option that may allow better visualization of the needle shaft and tip and offers the safety of imaging surrounding structures in the same view, thus capitalizing on the strengths of both the SAX and LAX approaches.

Two-dimensional imaging of the right IJ vein (IJV) and CA from the head of the patient over their right shoulder. (A) SAX, (B) LAX, (C) oblique axis. SAX imaging displays the lateral-right side of the patient on the right aspect of the display screen and the medial structures on the left aspect of the display screen. LAX imaging displays the caudad structures on the right aspect of the display screen and cephalad structures on the left aspect of the display screen. If the transducer is rotated counterclockwise about 30-40 degrees, oblique imaging displays more lateral-right caudad structures on the right aspect of the display screen, while more medial-left cephalad structures are on the left aspect of the display screen.

5. Real-Time Imaging Versus Static Imaging

Ultrasound guidance for vascular access is most effective when used in real time (during needle advancement) with a sterile technique that includes sterile gel and sterile probe covers. The needle is observed on the image display and simultaneously directed toward the target vessel, away from surrounding structures, and advanced to an appropriate depth. Static ultrasound imaging uses ultrasound imaging to identify the site of needle entry on the skin over the underlying vessel and offers the appeal of nonsterile imaging, which obviates the need for sterile probe coverings, sterile ultrasound gels, and needle guides. If ultrasound is used to mark the skin for subsequent cannulation without real-time (dynamic) use, ultrasound becomes a vessel locator technique that enhances external landmarks rather than a technique that guides the needle into the vessel. Both static and real-time ultrasound-guided approaches are superior to a traditional landmark-guided approach. Although the real-time ultrasound guidance outperforms the static skin-marking ultrasound approach, complication rates are similar.

Venous puncture using real-time ultrasound was faster and required fewer needle passes among neonates and infants randomly assigned to real-time ultrasound-assisted IJ venous catheterization versus ultrasound-guided skin marking. Fewer than three attempts were made in 100% of patients in the real-time group, compared with 74% of patients in the skin-marking group ( P < .01). In this study, a hematoma and an arterial puncture occurred in one patient each in the skin-marking group.

One operator can usually perform real-time ultrasound-guided cannulation. The nondominant hand holds the ultrasound probe while the dominant hand controls the needle. Successful cannulation of the vessel is confirmed by direct vision of the needle entering the vessel and with blood entering the attached syringe during aspiration. The probe is set aside on the sterile field, the syringe removed, and the wire is inserted through the needle. Further confirmation of successful cannulation occurs with ultrasound visualization of the guide wire in the vessel. Difficult catheterization may benefit from a second person with sterile gloves and gown assisting the primary operator by either holding the transducer or passing the guide wire.

6. Vessel Identification

Morphologic and anatomic characteristics can be used to distinguish a vein from an artery with 2D ultrasound. For example, the IJ vein has an elliptical shape and is larger and more collapsible with modest external surface pressure than the carotid artery (CA), which has rounder shape, thicker wall, and smaller diameter ( Figure 4 ). The IJ vein diameter varies depending on the position and fluid status of the patient. Patients should be placed in Trendelenburg position to increase the diameter of the jugular veins and reduce the risk for air embolism when cannulating the SC vein, unless this maneuver is contraindicated. A Valsalva maneuver will further augment their diameter and is particularly useful in hypovolemic patients. Adding Doppler, if available, can further distinguish whether the vessel is a vein or an artery. Color flow Doppler demonstrates pulsatile blood flow in an artery in either SAX or LAX orientation. A lower Nyquist scale is typically required to image lower velocity venous blood flows. At these reduced settings, venous blood flow is uniform in color and present during systole and diastole with laminar flow, whereas arterial blood flow will alias and be detected predominantly during systole ( Figure 5 ) in patients with unidirectional arterial flow (absence of aortic regurgitation). A small pulsed-wave Doppler sample volume within the vessel lumen displays a characteristic systolic flow within an artery, while at the same velocity range displays biphasic systolic and diastolic flow and reduced velocity in a vein. A lower pulsed-wave Doppler velocity range makes this distinction more apparent ( Figure 6 ).

Vessel identification. Right IJ vein ( top ) and CA ( bottom ) in SAX and LAX orientation. Slight external pressure compresses the oval-shaped vein but not the round-shaped artery.

Vessel identification with color flow Doppler. Arterial flow is visible in systole only, irrespective of Nyquist limit. Venous flow is visible in systole and diastole, but only if the Nyquist limit is sufficiently decreased.

Vessel identification with pulsed-wave Doppler will distinguish artery (A) from vein (B) at a Nyquist limit of ±50 cm/sec. Arterial blood flow has a predominately systolic component and higher velocity (A) compared with venous blood flow (B,C) , which has systolic and diastolic components and much lower velocity, better delineated with a lower Nyquist scale (±9 cm/sec) (C) .

Misidentification of the vessel with ultrasound is a common cause of unintentional arterial cannulation. Knowledge of the relative anatomic positions of the artery and vein in the particular location selected for cannulation is essential and is discussed below in the specific sections. Ultrasound images of veins and arteries have distinct characteristics. Veins are thin walled and compressible and may have respiratory-related changes in diameter. In contrast, arteries are thicker walled, not readily compressed by external pressure applied with the ultrasound probe, and pulsatile during normal cardiac physiologic conditions. Obviously, arterial pulsatility cannot be used to identify an artery during clinical conditions such as cardiopulmonary bypass, nonpulsatile ventricular circulatory assistance, and cardiac or circulatory arrest. Confirmation of correct catheter placement into the intended vascular structure is covered later in this document.

7. Internal Jugular Vein Cannulation

7.1. Anatomic Considerations

The IJ is classically described as exiting the external jugular foramen at the base of the skull posterior to the internal carotid and coursing toward an anterolateral position (in relation to the carotid) as it travels caudally. Textbook anatomy does not exist in all adult and pediatric patients. Denys and Uretsky showed that the IJ was located anterolateral to the CA in 92%, >1 cm lateral to the carotid in 1%, medial to the carotid in 2%, and outside of the path predicted by landmarks in 5.5% of patients. The anatomy of the IJ is sufficiently different among individual patients to complicate vascular access with a “blind” landmark method ( Figure 7 ). Therefore at a minimum, a clear and intuitive advantage of using static ultrasound imaging for skin marking is the ability to identify patients in whom the landmark technique is not likely to be successful.

Variable overlap between CA and IJ vein. RIJV , Right IJ vein.

Adapted from J Vasc Interv Radiol .

7.2. Cannulation Technique

The traditional approach to IJ vein cannulation uses external anatomic structures to locate the vein. A common approach identifies a triangle subtended by the two heads of the sternocleidomastoid muscle and the clavicle ( Figure 8 ). A needle placed at the apex of this triangle and directed toward the ipsilateral nipple should encounter the IJ 1.0 to 1.5 cm beneath the skin surface. The use of external landmarks to gain access to the central venous system is considered a safe technique in experienced hands. A failure rate of 7.0% to 19.4% is due partly to the inability of external landmarks to precisely correlate with the location of the vessel. Furthermore, when initial landmark-guided attempts are unsuccessful, successful cannulation diminishes to <25% per subsequent attempt. Additionally, there exists a strong direct correlation between the number of attempts and the incidence of complications, increasing patient anxiety and discomfort, and potentially delaying monitoring and infusion of fluids or medications necessary for definitive care. These are important quality of care issues that must be considered when choosing the best technique for central venous access.

External landmarks for IJ cannulation. SCM , Sternocleidomastoid muscle.

Modified from N Engl J Med .

Many studies have shown a clear advantage of ultrasound guidance over landmark guidance for IJ central venous cannulation. Troianos et al. demonstrated that the overall success rate of central venous cannulation could be improved from 96% to 100% with the use of ultrasound. This may not seem significant until one considers the improved first attempt success rate (from 54% to 73%), decreased needle advances (from 2.8 to 1.4 attempts), decreased time to cannulation (from 117 to 61 sec), and lower rate of arterial punctures (from 8.43% to 1.39%).

Several ultrasound studies have elucidated the anatomic relation between the IJ and CA, particularly in terms of vessel overlap. Sulek et al. prospectively examined the effect of head position on the relative position of the CA and the IJ. The percentage of overlap between the IJ and the CA increased as the head was rotated contralaterally from neutral (0°) to 40° to 80°. Troianos et al. found >75% overlap among 54% of all patients whose heads were rotated to the contralateral side (image plane positioned in the direction of the cannulating needle; Figure 9 ). Additionally, two thirds of older patients (age ≥ 60 years) had >75% overlap of the IJ and CA. Age was the only demographic factor that was associated with vessel overlap. The concern is that vessel overlap increases the likelihood of unintentional CA puncture by a through-and-through puncture of the vein. The accidental penetration of the posterior vessel wall can occur despite the use of ultrasound when the SAX imaging view is used for guidance. Typically, the anterior wall of the vein is compressed as the needle approaches the vein ( Figure 10 ). The compressive effect terminates as the needle enters the vein (heralded by the aspiration of blood into the syringe) and the vessel assumes its normal shape. A low-pressure IJ may partially or completely compress during needle advancement, causing puncture of the anterior and posterior walls without blood aspiration into the syringe. IJ-CA overlap increases the possibility of unintentional arterial puncture as the “margin of safety” decreases. Some authors have describe the “margin of safety” as the distance between the midpoint of the IJ and the lateral border of the CA. This zone represents the area of nonoverlap between the IJ and CA. The margin of safety decreases, and the percentage overlap increases from 29% to 42% to 72% as the head is turned to the contralateral side from 0° (neutral) to 45° to 90°, respectively. Vessel overlap increasing with head rotation is most apparent among patients with increased body surface areas (>1.87 m ² ) and increased body mass indexes (>25 kg/m ² ). Ultrasound can be used to alter the approach angle to avoid this mechanism of CA puncture by directing the advancing needle away from the CA ( Figure 11 ). Vascular anomalies and anatomic variations of the IJ and surrounding tissues have been observed in up to 36% of patients. Ultrasound identifies the vein size and location, anomalies, and vessel patency, thus avoiding futile attempts in patients with absent or thrombosed veins and congenital anomalies such as persistent left superior vena cava. Denys et al. observed small fixed IJs in 3% of patients. An ultrasound vein diameter < 7 mm (cross-sectional area < 0.4 cm ² ) is associated with decreased cannulation success, prompting redirection to another access site, thus reducing cannulation time and patient discomfort. Ultrasound also identifies disparity in patency and size between the right IJ and the left IJ (the right IJ usually larger than the left IJ). Maneuvers that increase the size of the IJ and thus potentially improve the cannulation success include the Valsalva maneuver ( Figure 12 ) and the Trendelenburg position.

Magnetic resonance imaging of neck anatomy. Contralateral turn of the neck increases the overlap between IJ vein (v) and CA (a).

From Anesthesiology .

The anterior wall of the IJ vein (IJV) recesses as the needle approaches the vein ( left ). The vein assumes its normal shape after the needle penetrates its wall ( right ).

Under ultrasound guidance, the needle approach to the IJ vein (IJV) can be altered to avoid CA puncture.

From Cardiovasc Intervent Radiol .

The size of the IJ vein (IJV) is increased with a Valsalva maneuver (B) compared with apnea (A) .

8. Subclavian Vein Cannulation

8.2. Cannulation Technique

The landmark-guided approach to the central venous circulation via the SC vein is generally considered by many clinicians to be the simplest method to access this vein. Several million SC vein catheters are placed each year in the United States. The risk factors for complications and failures are poorly understood, with the exception of physician experience. Advantages of using the SC vein for central venous access include consistent surface anatomic landmarks and vein location, patient comfort, and lower potential for infection. In contrast to attempted IJ vein cannulation, in which unintentional injury to the adjacent CA can compromise circulation to the brain, unintentional injury to the adjacent SC artery during SC vein cannulation carries a less morbid sequela. The physician’s experience and comfort level with the procedure are the main determinants for successful placement of a SC vein catheter, when there are no other patient-related factors that increase the incidence of complications. The SC vein may be cannulated from a supraclavicular or an infraclavicular approach. The infraclavicular approach is the most common approach and hence is the focus of this discussion. The supraclavicular approach (without ultrasound) has largely been abandoned because of a high incidence of pneumothorax. As experience with ultrasound-guided regional anesthesia for upper extremity blocks has increased imaging and identification of the supraclavicular vessels and nerves, clinicians are gaining more familiarity with imaging the supraclavicular approach to the SC vein using ultrasound for vessel cannulation. Whether this approach will continue to gain popularity remains to be demonstrated.

Tau et al. analyzed anatomic sections of the clavicle and SC vein and determined that the supine position with neutral shoulder position and slight retraction of the shoulders was the most effective method to align the vein for a landmark-based technique. Although many clinicians place patients in the Trendelenburg (head-down) position to distend the central venous circulation, there is less vessel distention of the SC vein than the IJ vein because the SC vein is fixed within the surrounding tissue, so relative changes in size are not realized to the same degree as with the IJ vein. Thus, the primary reason for the Trendelenburg position is to reduce the risk for air embolism in spontaneously breathing patients.

Ultrasound-directed vascular cannulation may lead inexperienced operators to use needle angle approaches that lead to an increased risk for complications. It is important that traditional approaches and techniques are not abandoned with ultrasound guidance, particularly during cannulation of the SC vein, in which a steeper needle entry angle may lead to pleural puncture. The needle is directed toward the sternal notch in the coronal plane. The bevel of the needle should be directed anteriorly during insertion and gentle aspiration applied with a syringe, as the needle enters the skin at a very low (nearly parallel) angle to the chest wall. An increased or steeper angle increases the likelihood of creating a pneumothorax. The needle bevel may be turned caudally upon venopuncture to direct the guide wire toward the right atrium. The wire is advanced, leaving enough wire outside the skin for advancement of the entire catheter length over the wire (i.e., the wire should extend beyond the catheter outside the skin). The electrocardiogram should be closely monitored for ectopy that may occur when the wire is advanced into the right atrium or right ventricle. Chest radiography is mandatory not only to confirm proper line placement but also to rule out pneumothorax.

Similar preparation of the patient occurs with ultrasound-guided cannulation as with the landmark-guided approach with respect to positioning, skin preparation, and vascular access kits. The use of a smaller footprint transducer probe for SC vein access for real-time ultrasound imaging is recommended because larger probes make imaging of the vein more challenging. It is generally more difficult to position the larger footprint probe between the clavicle and rib to obtain an adequate SC vein image. Despite some loss of resolution in the far field that inherently occurs with phased-array transducers, smaller probes may allow better maneuverability underneath the clavicle. Similar to the landmark technique, the middle third of the clavicle is chosen as the site used for ultrasound imaging and subsequent needle insertion. The transducer is oriented to image the SC vein in the SAX view with a coronal imaging plane. The vein appears as an echo-lucent structure beneath the clavicle ( Figure 13 ). It is important to distinguish between pulsatility on the vein due to respiratory variation and pulsatility of the artery. Confirmation of the venous circulation can be facilitated by the injection of agitated saline “echo contrast” into a vein of the ipsilateral arm (if available) with subsequent imaging of the microbubbles in the vein. Confirmation can also be achieved by addition of color flow Doppler to the ultrasound assessment. When positioning the transducer marker toward the left shoulder (during right SC vein cannulation), arterial flow will be the color that indicates flow away from the transducer, while venous flow will be the color that indicates flow toward the transducer. It is important to ensure correct transducer orientation before using color flow Doppler to determine the identification of artery or vein. Considerable skin pressure is required to obtain adequate imaging planes (windows) that may incur some patient discomfort.

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