INTRODUCTION — Establishing venous access is critically important and can be technically challenging at times. The use of ultrasound to guide catheter placement reduces the number of access attempts and may reduce other complications as well [1-8]. Ultrasound guidance can be used for placing central venous catheters as well as for placing peripheral venous catheters. Clinicians who place central venous access devices (occasionally or frequently) are strongly encouraged to learn ultrasound-guided techniques [3,4].
The principles of ultrasound-guided venous access in adults, with considerations for pediatric populations, are reviewed. A general overview, including central vein anatomy, types of venous devices and their selection, and techniques for central venous access at specific sites, is presented separately. (See "Central venous access: General principles" and "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies" and "Placement of femoral venous catheters" and "Placement of subclavian venous catheters" and "Placement of jugular venous catheters".)
ACCESS SITES — A central venous access device is defined as a catheter that has its tip located in the superior vena cava, right atrium, or inferior vena cava.
Central venous catheters include:
●Those that are placed into the thoracic central veins via an access site in the proximal upper extremity or neck (eg, subclavian vein, axillary vein, internal jugular vein, external jugular vein, proximal cephalic vein). (See 'Supraclavicular venous access' below and 'Infraclavicular venous access' below.)
●Those that are placed into the abdominal central veins via an access site in the groin (eg, common femoral vein, femoral vein, great saphenous vein). (See 'Femoral veins' below.)
●Those that are placed into the central veins through a peripheral venous access site, typically in the upper extremity (eg, basilic vein, brachial vein, distal cephalic vein). (See 'Peripheral veins' below.)
Real-time dynamic ultrasound-guided venipuncture can be used at any of these sites. The only central venous access devices for which ultrasound guidance cannot be used are epicutaneo-caval catheters in neonates, for which the catheter is inserted in a superficial vein, and umbilical venous catheters, for which the catheter is inserted directly into an open vein. Percutaneous placement of other central venous access in a neonate is typically performed with ultrasound guidance.
GLOBAL USE OF ULTRASOUND — A new concept termed "the global use of ultrasound" acknowledges the role of ultrasound for many different aspects of venous access, from planning access to guiding insertion, and for identifying early and late complications [5,9]. This practice shift is not surprising, given the wide application of ultrasound in other areas, particularly in the management of critically ill patients [10,11].
Ultrasound guidance is beneficial during venipuncture, but ultrasound can also be used to choose the most appropriate vein , determine the presence of anatomic variations, rule out any venous thrombosis, check the progression of the guidewire and/or the catheter into the venous system (ie, "tip navigation") [13,14], rule out early puncture-related complications (eg, pneumothorax, local hematoma) [15-17], assess the central location of the tip (ie, "tip location," by echocardiography) [18,19], and rule out late complications (tip migration, catheter-related venous thrombosis, fibroblastic sleeve formation) .
Ultrasound use can reduce complications by reducing the number of unsuccessful access attempts. Multiple needle passes are associated with a higher risk of pneumothorax, arterial puncture, and nerve injury. In addition, multiple needle passes increase the risk of perivascular hematoma or vasospasm, either of which can result in greater technical difficulty cannulating the vessel and may increase the risk of catheter-associated thrombus due to diminished blood flow around the catheter. Improvements in first-attempt success rates will also reduce patient stress and pain and increase patient satisfaction. Ultrasound measurement of the size of the vein to be accessed can help with selection of an appropriate catheter size, which can reduce the risk of thrombotic and infective complications [4,20,21]. (See "Catheter-related upper extremity venous thrombosis in adults", section on 'Catheter-related factors'.)
Recommendations — Based upon randomized trials and multidisciplinary consensus guidelines [4,5,13,16,18-20,22-25], we recommend the following for the placement and management of central venous access (see 'Use of ultrasound and efficacy at specific sites' below):
●Ultrasound equipment and properly trained operators should be available for central venous access.
●The ultrasound-guided venipuncture should be preceded by a determination of the most appropriate vein for access, based upon systematic ultrasound evaluation of possible access sites.
●The venipuncture should be performed using dynamic "real-time" ultrasound guidance, not "static" ultrasound localization of the vein with subsequent "blind" venipuncture . (See 'Dynamic ultrasound techniques' below.)
●After the venous cannulation, ultrasound should be used to assess for possible complications, including arterial injury, pneumothorax, or catheter malposition.
Dynamic real-time ultrasound guidance during needle placement is recommended by numerous safety advocacy organizations and professional societies [1,3,4,7,8,21,22,26-37]. It is the preferred technique for all central venous access procedures . Randomized trials and observational studies in pediatric and adult patient populations have demonstrated that dynamic ultrasound imaging during needle placement reduces time to venous cannulation and reduces the risk of insertion-related complications thereby increasing safety and quality of central venous access [20,22,38-41]. The level of benefit varies depending upon operator skill, anatomic site, quality of the materials used (eg, ultrasound device, needle), and comorbid clinical conditions. Thus, proper equipment should be available whenever a central line is required, and operators should be properly trained in the use of ultrasound equipment.
These recommendations are supported by guidelines issued by safety advocacy organizations including the Agency for Healthcare Quality and Research, the National Institute for Health and Care Excellence (NICE), and multiple professional societies, including the American Institute of Ultrasound in Medicine, European Federation of Societies for Ultrasound in Medicine and Biology, American Society of Anesthesiologists Task Force on Venous Access, American Society of Echocardiography, Society of Cardiovascular Anesthesiologists, WoCoVA Foundation, Society of Hospital Medicine, British Society of Anesthesia, Italian Group of Venous Access Devices (GAVeCeLT), French group of venous access (GIFAV), UK-based group called EPIC, Scandinavian Society of Anesthesiology, and many other national associations from different countries [1,3,7,8,21,27-37,42].
Contraindications and precautions — Other options for rapid vascular access (eg, interosseous access) may be appropriate in life-threatening situations. (See "Intraosseous infusion" and "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies".)
If emergency central venous access is needed and ultrasound guidance is not immediately available, landmark-based placement of a femorally inserted central catheter (FICC) is preferred, but the FICC should be removed and replaced with an ultrasound-guided centrally inserted central catheter (CICC) or peripherally inserted central catheter (PICC) within 48 hours. (See "Central venous access: Device and site selection in adults".)
Limitations and shortcomings related to the use of ultrasound include the following:
●Ultrasound resolution decreases with depth. Vascular structures in morbidly obese patients may be difficult to visualize and access.
●Subcutaneous emphysema (ie, air in the tissues) in the region of the access site may block ultrasound transmission.
●Volume depletion may increase the difficulty of central venous access by reducing the vein caliber. Rapid Central Vein Assessment (RaCeVA) may help to select the best approach for ultrasound-guided cannulation in hypovolemic patients [12,43]. (See 'Preprocedural vein imaging' below.)
Other contraindications or precautions are the same as for other vascular access procedures (table 1). (See "Central venous access: General principles", section on 'Relative contraindications'.)
USE OF ULTRASOUND AND EFFICACY AT SPECIFIC SITES
Supraclavicular venous access
Internal jugular — Most of the experience in the literature regards the use of ultrasound for internal jugular cannulation [44-46]:
●A systematic review evaluated the overall effectiveness of ultrasound-guided jugular venous catheter placement in 35 trials with 5108 participants . Compared with landmark techniques, ultrasound guidance increased the rate of successful catheter placement by 12 percent (pooled outcome, 25 trials) and successful first attempt by 57 percent (pooled outcome, 18 trials) and reduced the time needed for successful cannulation. The overall incidence of complications was reduced by 71 percent (pooled outcome, 14 trials), as was the incidence of inadvertent arterial puncture.
●In an earlier meta-analysis, seven trials including 608 adults and three trials including 167 infants undergoing internal jugular cannulation were included . The rate of successful placement was significantly higher for dynamic ultrasound-guided compared with landmark-based techniques (99 versus 78 percent) in both adults and infants. Failure on the first attempt was significantly reduced from 57 to 33 percent in adults. On average, there were significantly fewer total numbers of attempts in adults and infants (1.5 and 2 mean fewer needle passes, respectively). Complications, predominantly arterial puncture, were significantly reduced from 16 to 5 percent in adults and from 30 to 6 percent in infants.
●Another meta-analysis examined the real-time ultrasound guidance for central venous catheter insertion in pediatric patients <18 years of age . This meta-analysis included eight trials involving 760 patients and reported that ultrasound-guided central venous catheter insertion significantly increased success rates by 31.8 percent along with a decrease in the mean number of attempts required. A trend toward a decrease in the risk of accidental arterial puncture was also observed. The time required to place the catheters was similar for ultrasound-guided and landmark-based techniques.
●A separate systematic review identified five trials in children comparing dynamic ultrasound with the landmark technique for cannulating the internal jugular vein . The best of these (judged to be at low risk of bias) had a significantly higher success at first attempt for ultrasound compared with the landmark technique (65 versus 45 percent) . Success within three attempts was achieved in 95 percent of the ultrasound group compared with 74 percent of the landmark group.
Other advanced supraclavicular vein options — Ultrasound can guide supraclavicular access to other thoracic veins, such as the brachiocephalic vein in children and neonates [4,6]. The external jugular vein can also be accessed by ultrasound where it is deep, running parallel, posterior, and superior to the subclavian vein. A supraclavicular approach to the subclavian vein has also been described, though it is associated with a higher risk of pleural puncture.
Infraclavicular venous access — When central veins are accessed from an infraclavicular approach, clinical studies have been less consistent in defining the benefits of ultrasound guidance [48,49]. Still, evidence suggests that ultrasound guidance improves the success rate, decreases the risk of puncture-related complications, and decreases the length of time for the procedure compared with "blind" landmark techniques [22,38,48,50-56].
In a meta-analysis of three trials, direct (ie, dynamic) ultrasound significantly reduced the risk of inadvertent arterial puncture (relative risk [RR] 0.21, 95% CI 0.06-0.82) and hematoma formation (RR 0.26, 95% CI 0.09-0.76) but not other complications [48,50,52,54]. There were no significant differences in number of attempts until success, first-time success rates, or time taken to insert the catheter. In a separate meta-analysis of five trials, dynamic ultrasound also significantly reduced inadvertent arterial puncture and hematoma formation, but also pneumothorax . Among five trials, the failed catheterization rate was also significantly reduced (RR 0.24, 95% CI 0.06-0.92).
The potential advantages of an ultrasound-guided infraclavicular access to the axillary vein in terms of skin access site make this approach one of the most useful sites in critically ill patients, particularly for patients with a tracheostomy [55,57-60]. An ultrasound-guided infraclavicular approach to the cephalic vein has also been used . The advantages of this approach are avoidance of accidental injury to the axillary artery or to the pleura. Such an approach is possible only when the cephalic vein has a caliber appropriate to the diameter of the catheter to be inserted.
Ultrasound-guided subclavian venipuncture in small children may have peculiarities due to anatomic issues [22,62]. In neonates and infants, the clavicle is not an obstacle for ultrasound, so a combined infraclavicular-supraclavicular approach to the subclavian vein is possible. However, the caliber of the axillary vein is often so small that placement of a catheter, though technically feasible, is not recommended because of the increased risk of venous thrombosis and/or stenosis. In addition, in children, and also in small adults, a catheter inserted by an infraclavicular approach may be more difficult to direct into the brachiocephalic vein compared with a catheter inserted by a supraclavicular approach .
Femoral veins — The common femoral vein (CFV) can be accessed in the groin . Studies of "femoral vein" access typically refer to the CFV, though successful ultrasound cannulation of the femoral vein at mid-thigh has also been described [63,64]. (See 'Ultrasound views' below and 'In-plane versus out-of-plane venipuncture' below.)
●For femoral vein access, the pooled success rate on the first attempt from three trials was significantly higher for ultrasound compared with landmark techniques (RR 1.73, 95% CI 1.34-2.22), and the overall success rate was increased (RR 1.11, 95% CI 1.00-1.23) . There were no significant differences in the rate of inadvertent arterial puncture or other complications
●In children (≤12 years) who were undergoing cardiac surgery, a trial comparing dynamic ultrasound with the landmark technique found that while the success rate for femoral vein cannulation was the same in both groups (96 percent), those in the ultrasound group had a significantly higher rate of successful cannulation on the first pass (75 versus 25 percent) and a significantly shorter time to complete cannulation (median time 155 versus 370 seconds) .
●In a meta-analysis of four trials involving 4065 subjects [66-69], ultrasound-guided femoral vein cannulation for electrophysiologic procedure reduced major vascular bleeding (RR 0.40, 95% CI 0.28-0.91) as well as minor vascular complications (RR 0.34, 95% CI 0.15-0.78) .
Peripherally inserted central catheters — Considering the special features of peripherally inserted central catheters (PICCs), ultrasound is obviously very important for choosing the most appropriate vein (ie, preprocedural scan) and for "tip navigation" (ie, control of the proper direction of the catheter into the brachiocephalic vein using supraclavicular ultrasound).
Ultrasound guidance is also required for the placement of PICCs to avoid puncture-related complications (ie, avoiding the brachial artery and median nerve) [3,35]. Ultrasound guidance has had a dramatic impact on the overall clinical performance of PICCs. When PICCs were first introduced, they were typically inserted by puncture and cannulation of the visible/palpable veins of the antecubital fossa, a practice now abandoned. Simply by moving the access site from the superficial veins of the antecubital area to the deeper veins in the middle third of the upper arm, ultrasound guidance has been associated with a 95 to 99 percent rate of successful cannulation and a substantial decrease in early and late complications.
Peripheral intravenous devices — Ultrasound guidance is also useful for peripheral intravenous (PIV) access when difficulty is expected or when the blind technique has failed [4,71-78]. This can be achieved either by ultrasound-guided placement of a standard midline catheter in a vein of the upper arm or by ultrasound-guided placement of a short or long peripheral cannula in a vein of the forearm or of the antecubital fossa.
Adults with difficult access — When short peripheral cannulas are used, the expected duration of the intravenous line is limited. Thus, if the line is needed for more than 48 hours in adults, most authors recommend inserting either a long peripheral cannula or a midline catheter. The choice depends on the expected duration and the clinical setting (hospital versus home care). (See "Central venous access: Device and site selection in adults".)
Near-infrared (NIR) imaging is useful to guide placement of peripheral intravenous catheters in upper extremity (forearm or upper arm) superficial veins. Ultrasound is preferred for access of veins that are >7 mm deep to the surface . (See "Peripheral venous access in adults", section on 'Tools for locating veins' and "Peripheral venous access in adults", section on 'Ultrasound guided'.)
A systematic review identified seven trials (adults) using ultrasound to assist the placement of peripheral intravenous catheters . Among six trials, successful cannulation was significantly more frequent with ultrasound guidance compared with no ultrasound guidance (79 versus 62 percent). There were no significant differences in time to successful cannulation (five trials) or number of percutaneous skin punctures (four trials). A separate systematic review found a reduced number of attempts in a pooled analysis of four trials in adults .
Children with difficult access — In the pediatric population, visual inspection, palpation, or NIR imaging can localize potential peripheral veins for cannulation [78,81-83]. The use of ultrasound for guidance can be hampered by the small size of the child's extremity and lack of cooperation during the procedure [81,84,85]. Thus, for most children, based on data from randomized trials, the most appropriate initial method for obtaining PIV access remains the standard (landmark) approach, particularly when the operator has reasonable confidence that an accessible vein is visible or palpable. However, for children who are likely to have difficult intravenous access (DIVA; eg, no visible or palpable veins, younger age, increased subcutaneous fat, dehydration) or in whom previous attempts have already failed (no peripheral access after three attempts by an experienced clinician), we suggest ultrasound guidance for central venous access. In neonates, ultrasound has no role in peripheral venous access; NIR imaging may be useful.
Two large randomized trials have addressed the use of ultrasound for PIV line placement in unselected pediatric populations [86,87]. Success rates were similar for ultrasound-guided compared with landmark techniques in each of these trials. In the larger trial, the rate of first-attempt success was also similar for an ultrasound-guided technique compared with NIR imaging . Among children three years and younger, there was also no significant difference in success rates for ultrasound imaging compared with standard approach to PIV placement.
The DIVA score is a validated clinical prediction tool that can help identify children who are likely to have a high first-attempt failure rate using standard techniques . In children with DIVA, ultrasound guidance aids PIV placement. In a meta-analysis (unselected patients [2 trials] [86,87], patients with DIVA [6 trials]), first-attempt success and overall success rates were significantly improved for ultrasound-guided compared with standard techniques . Meta-analysis of data comparing ultrasound guidance with standard techniques in patients with DIVA showed a significantly improved first-attempt success rate (odds ratio [OR] 4.6, 95% CI 2.34-9.07) as well as overall success rate (OR 3.34, 95% CI 1.89-5.87) . In addition to DIVA, improved success of ultrasound guidance was associated with other characteristics including patient age ≤3, physician operator, use of sedation, operating room setting, certain ultrasound techniques (ie, dynamic, single operator, short axis), and access site (ie, lower extremity).
Intraosseous access — Ultrasound has also been used to confirm intraosseous (IO) needle placement in adults. The efficacy of this approach was illustrated in a human cadaver study . Detection of Doppler flow within the marrow cavity when the ultrasound probe was placed cephalad to the IO access site correctly predicted appropriate IO access placement in all instances and was superior to assessing drops from the IV fluid bag into the IV tubing reservoir.
ULTRASOUND EQUIPMENT — The level of sophistication of ultrasound equipment varies widely, but even the most basic models are usually sufficient for the purposes of ultrasound-guided venous access, although higher quality units will likely achieve better results.
Modes — Requirements for vessel identification and localization for cannulation include B-mode and Doppler mode. B-mode (brightness mode) refers to the standard two-dimensional grayscale image of the tissue, while Doppler mode relies on the flow of blood either toward or away from the transducer to provide velocity information.
Duplex ultrasound refers to the simultaneous display of a color Doppler image and the spectral waveform. Flow velocities can be presented graphically on a timeline (spectral or pulsed Doppler). Color Doppler provides velocity information presented as colors superimposed on a grayscale image. The clinician should keep in mind that both color and spectral Doppler are least sensitive when the vessel is oriented 90 degrees to the transducer since the flow toward the transducer and away from the transducer are equal. If the operator encounters difficulty in identifying flow with color or spectral Doppler, tilting the probe so that the vessel is not horizontally oriented in the image may help achieve a better Doppler angle.
Most ultrasound-guided venipunctures will benefit from a standard two-dimensional imaging. Temporal resolution is best in the 2-D mode (without Doppler). Visualization of vein flow with color Doppler or pulsed Doppler has a limited role in ultrasound-guided venipuncture, although it is useful for detecting late complications of central venous access such as venous thrombosis.
Transducers — Proper probe selection is important. For vascular access, a high-frequency (5 to 15 MHz) linear transducer is usually best (picture 1).
●The high-frequency linear transducer (5 to 10 MHz) is most commonly used for ultrasound-guided centrally inserted central catheters (CICCs) and femoral vein inserted central catheters (FICCs) (picture 1). The high frequency permits greater resolution of tissues close to the skin surface. A linear (flat) shape is ideal for imaging veins because it allows the operator to evenly apply compression to distinguish arteries from veins (image 1 and image 2).
●The "hockey-stick" 10 to 15 MHz transducer is a very high-resolution linear transducer, which allows the greatest degree of needle and vein visibility. It is appropriate for ultrasound-guided CICCs and FICCs in neonates, infants, and in children, but also for ultrasound-guided peripherally inserted central catheters (PICCs) at any age (picture 1). In the pediatric population, this is the ideal probe for venous access at any site and will be sufficient for most pediatric venous access needs. It is limited by its shallow penetration, which might make it unsuitable for large or obese adults. It is certainly ideal for placing PICCs, both in children and in adults, since the veins that need to be accessed are generally within 2 cm of the surface of the skin.
ULTRASOUND EVALUATION OF VESSELS — A systematic evaluation of veins in the areas of interest is recommended. (See 'Preprocedural vein imaging' below.)
When seen with ultrasound, the lumen of a normal vessel is anechoic (black), while the surrounding tissues will be some level of gray. Veins are generally easily distinguished from arteries on ultrasound (table 2). Veins are oval shaped with thin walls and are more easily compressed with light pressure, while arteries are generally circular with thicker walls and less easily compressed (image 1). Veins also lack arterial pulsations and may have visible valves (image 1 and image 2). In addition, veins usually distend with maneuvers that impede or augment venous return, such as application of limb tourniquets, the Valsalva maneuver, or putting the patient in the Trendelenburg position.
Arterial diameter will remain the same during the above mentioned maneuvers. If the grayscale appearance of a vessel is not convincingly a vein based upon the above criteria, Doppler ultrasound can be used. Arterial flow is generally distinctly pulsatile with a sharp "whoosh" sound corresponding to systole. Conversely, venous flow produces a steadier "hum" that often becomes more pulsatile the closer the vein is to the heart. With color Doppler, be aware that the red and blue colors are arbitrary, indicating only the direction of flow relative to the transducer location, not the type of vessel. By convention, red is defined as flow toward the transducer and blue represents flow away from the transducer, but this orientation can be switched using the control panel on the ultrasound machine or reversing the orientation of the probe. These issues are associated with a significant incidence of errors of interpretation, such that routine use of color Doppler for this purpose is not recommended.
While spectral Doppler waveform depiction of flow may be useful (coupled with color Doppler) for detecting late complications such as catheter-related venous thrombosis, it has no major role in the performance of ultrasound-guided venipuncture. (See 'Modes' above.)
When in question, though, Doppler can be helpful in distinguishing an artery from a vein (image 1 and image 2). Arteries produce a waveform with a sharp upstroke (waveform 1). Veins produce an undulating waveform that shows variation with the respiratory and cardiac cycles (waveform 2). The degree of variation will depend upon the depth of breathing as well as the proximity of the vein to the right atrium.
Probe orientation — It is important that the operator orient the probe properly. Probes usually have markings to assist with proper probe orientation. By convention, structures beneath the left aspect of the ultrasound probe marker (denoted by a light or a notch on the side of the probe) are always displayed on the left side of the imaging screen. If the probe markings are obscured, movement of the probe left or right while observing the image helps confirm the proper orientation .
If the operator notices that the configuration is opposite of what is expected (that is, structures under the left side of the probe are seen on the right side of the display screen), then rotating the probe 180 degrees will correct the orientation. An exception is when using the "hockey-stick" probe, which is ergonomically designed to be held in the hand a specific way. In this case, the display screen should be flipped ("left/right" adjustment) to create the proper orientation. The key point is for the operator to ensure that the probe or the screen display is oriented such that when the needle tip is directed toward the operator's left, the needle tip moves toward the left on the screen display. This will create the most intuitive arrangement; any other orientation will unnecessarily increase the technical difficulty of the procedure.
The position of the operator at the head of the bed is needed for two special approaches to the internal jugular vein (ie, out-of-plane short axis, in-plane long axis) (see 'In-plane versus out-of-plane venipuncture' below). In these cases, the probe marker should be oriented toward the operator's left (also the patient's left) for both right and left internal jugular vein access. However, because of the high risk of puncture-related complications and less desirable location of the catheter exit site, these two approaches to the internal jugular vein are less appropriate compared with others and are discouraged.
Ultrasound views — Transverse (short axis) and longitudinal views (long axis) are used to localize and visualize the selected vein [91,92]. The view used may depend upon the vein selected for access and the patient's surface anatomy.
The transverse (short-axis) view is useful for identifying vessels near the skin surface, such as the internal jugular vein or the deep veins of the upper extremity. For other vessels, a combination of views can be used; the transverse view may be easier for vein localization while the longitudinal view may provide more information about the actual diameter of the vein, the presence of valves, and vein morphology. Imaging the vein from two directions may give more information about the local anatomy and thus reduce the potential for damage to surrounding structures .
One trial compared the occurrence of posterior wall puncture using a short-axis out-of-plane (40 patients), long-axis in-plane (40 patients), or combined short-axis-and-long-axis (40 patients) approach . Successful guidewire insertion without posterior wall puncture was performed in 100 percent of patients in the combined short-axis-and-long-axis approach group, 70 percent in the short-axis out-of-plane approach group, and 95 percent in the long-axis in-plane approach group.
Short axis (transverse) view — The transverse view is obtained with the probe at a 90-degree angle to the course of the vein. The vessels appear in cross section in this view ("short axis").
Using the transverse view coupled with the out-of-plane technique, the needle position is adjusted to ensure vessel entry at the 12 o'clock position. This technique minimizes the risk of accessing the lateral aspect of the vessel, which may be associated with perivascular hematoma, failure to cannulate, or more difficult hemostasis after catheter removal. Vein cannulation with the "out-of-plane short axis" technique is easier for two reasons.
●Distinguishing the vein from an adjacent artery with compression technique is best performed with transverse orientation of the probe. With a long axis approach, the operator can slide off axis from the vessel during compression, rather than truly compressing the vessel.
●The short axis approach also allows the operator to easily correct the trajectory of the needle during insertion through the tissues prior to venipuncture.
The time to successful cannulation may be less with the short axis view . However, for inexperienced operators, the needle tip is less easily seen compared with the longitudinal approach, so that there is some risk of injury to adjacent structures (eg, nerve or artery) or perforation of the posterior wall of the vein [92,95]. (See 'Long axis (longitudinal) view' below.)
Long axis (longitudinal) view — The longitudinal view, which is always associated with the "in-plane" technique, is ideal for the placement of centrally inserted central catheters (CICCs) in the brachiocephalic, subclavian, external jugular, and axillary veins [4,6,96,97]. This view is also very helpful for placement of femoral venous catheters and peripherally inserted central catheters (PICCs) in the lower extremities of neonates and infants. When accessing a vein with this technique, the clinician should first identify the location of the vein using the transverse view; the probe should then be rotated 90 degrees so that its long axis is parallel to the course of the vein (waveform 2). This view typically permits direct observation of needle penetration into the vein and passage of the guidewire (image 3).
In a simulated model of ultrasound-guided vascular access, the needle tip was seen in 24 of 39 cannulations using the longitudinal view . With proper training and proper choice of the material (good-quality ultrasound device, echogenic needles), it can be seen in 100 percent of cases. (See 'Dynamic ultrasound techniques' below.)
A potentially important limitation is that the longitudinal view may be technically more difficult to perform and to maintain the center of the vessel in view during vascular access procedures [92,93,98].
Oblique axis (oblique) view — An oblique view for ultrasound-guided visualization, puncture, and cannulation has been proposed for the internal jugular vein and for the axillary vein [99,100]. According to some authors, such an approach may have some advantages in terms of safety, though it requires more training. It is always performed as "in-plane" puncture.
In-plane versus out-of-plane venipuncture — The actual technique of puncture will be either "in plane" (needle parallel to the probe) or "out of plane" (needle perpendicular to the probe), which are terms that define the spatial relationship between the needle and the probe. Note that the term "short" or "transverse" axis describes only the spatial relationship between the probe and the vein. (See 'Probe orientation' above.)
●An ultrasound-guided venipuncture with identification of the vein in a transverse (short axis) view can be performed either as an "in-plane short axis" or as an "out-of-plane short axis" maneuver. The former is used exclusively for the internal jugular vein . The latter is commonly used for any PICC or FICC insertion, but it is also a possible approach for a CICC in the infraclavicular area (axillary vein or cephalic vein).
●Ultrasound-guided venipuncture with visualization of the vein in a longitudinal (long axis) view is performed exclusively as "in-plane long axis." It is typically used for the supraclavicular approach to the brachiocephalic, subclavian vein, and external jugular vein. It has also been adopted as one of the possible infraclavicular approaches to the axillary vein. An "out-of-plane long axis" approach, though theoretically feasible, has no role in clinical practice.
Planning the exit site plays a major role in the choice of the internal jugular vein approach . Most of the evidence suggests that some techniques of approach to the internal jugular vein (eg, the "in-plane short axis" approach) may be safer than others. The "out-of-plane short axis" approach is associated with an unfavorable exit site at mid-neck that is discouraged by most guidelines since the catheter may be more prone to infection and to dislodgement [21,28]. The "out-of-plane short axis" approach may also be associated with complications due to the accidental perforation of the posterior wall of the vein, with subsequent injury to the subclavian artery. (See 'Ultrasound views' above.)
The brachiocephalic, subclavian, and external jugular veins are all punctured and cannulated necessarily by an "in-plane long axis" approach.
Needle guidance systems — Needle guidance systems have been proposed to help facilitate both the in-plane and the out-of-plane approach. These systems typically use a sterile plastic guide for the needle that snaps onto the probe . The apparatus snaps apart after the target is reached, freeing the needle. One study of anesthesia residents showed that the use of a needle guidance system significantly increased needle tip visibility compared with the longitudinal free-hand technique or transverse technique . However, the number of needle sticks and needle redirections did not differ. In expert hands, needle guides are more of an obstacle than a benefit, reducing the flexibility of the maneuver. They might be useful exclusively as a teaching tool, specifically while learning out-of-plane short axis maneuvers.
PREPARATION — For ultrasound-guided venous access, preparatory steps (including use of sterile technique) are the same as with any vascular access procedure, with the added step of ultrasound equipment preparation . These are reviewed briefly below and discussed in more detail separately. (See "Central venous access: General principles", section on 'General preparation' and "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies", section on 'General approach'.)
Preparation specific to individual access sites is discussed in detail elsewhere. (See "Placement of subclavian venous catheters", section on 'General preparation' and "Placement of femoral venous catheters", section on 'General preparation' and "Placement of jugular venous catheters", section on 'General preparation'.)
Preprocedural vein imaging — Prior to the placement of any central catheter, ultrasound imaging should be used to evaluate all possible veins potentially useful for cannulation. Rapid Central Vein Assessment (RaCeVA) of all veins in the supraclavicular and infraclavicular area has been described [12,43]. RaCeVa includes insonation at the mid-neck, then base of the neck looking first toward the mediastinum, then laterally in the supraclavicular region, and finally in the infraclavicular region. Ultrasound evaluation of the axillary vein is equally important, since findings of a "difficult" axillary vein, such as small caliber, too deep, or collapsing at each inspiration, will suggest a benefit for using a supraclavicular vein.
The safest approach (which often corresponds to the easiest) is chosen only after the preprocedural scan . Two-dimensional ultrasound is used, with imaging encompassing the entire area of possible venous cannulation and verifying the caliber, patency, and position of the most relevant veins. Preprocedure duplex exam is usually not necessary. (See "Central venous access: General principles", section on 'Use of ultrasound' and "Central venous access: Device and site selection in adults", section on 'Access site' and "Central venous access: General principles", section on 'Device and site selection'.)
To avoid a high risk of causing catheter-associated thrombosis or chronic venous stenosis/occlusion, particular attention must be paid to the caliber of the vein. The inner diameter of the vein should be at least three times the external diameter of the catheter to reduce the risk of thrombosis. Multiple studies have shown that the risk of deep vein thrombosis (DVT) is correlated with increasing catheter diameter. (See "Catheter-related upper extremity venous thrombosis in adults", section on 'Catheter-related factors' and "Peripherally inserted central catheter (PICC)-related venous thrombosis in adults", section on 'Risk factors'.)
●One prospective cohort study of 136 adult patients undergoing peripherally inserted central catheter (PICC) placement found an optimal catheter-to-vein diameter cutoff ratio of 45 percent. Patients in the study with a catheter diameter that exceeded 45 percent of the vein diameter were 13 times more likely to have venous thromboembolism compared with patients with a catheter-to-vein ratio less than or equal to 45 percent .
●In an observational study of 265 PICC placements in children, one of the most significant risk factors for PICC-related superficial and deep venous thrombosis was a catheter-to-vein ratio of greater than 33 percent .
Infection control — Reduction of central line-associated bloodstream infections is one of the National Patient Safety Goals for hospitals currently promoted by the Joint Commission . Recognizing the importance of this patient safety goal, many hospitals have made this issue an organizational priority and have established protocols for patient preparation, dressings, and maintenance of central venous catheters. (See "Routine care and maintenance of intravenous devices".)
All operators must be familiar with their institutional-specific guidelines prior to placing central lines. Refer to the Centers for Disease Control and Prevention (CDC; United States) website for their checklist, which can serve as an example of the key elements that should be included in a central venous catheter placement policy . The cornerstones of infection prevention during central venous access, according to the CDC, Evidence-based Prevention and Infection Control (EPIC; United Kingdom), and Society of Healthcare Epidemiologists of America (SHEA; United States) guidelines, include the following [21,28]:
●Hand hygiene before starting the procedure.
●Maximal barrier precautions, which include nonsterile cap, nonsterile mask, sterile gloves, sterile gowns, wide sterile field over the patient (body drape covering at least 85 percent of the patient), and long sterile cover over the probe.
●Skin antisepsis with 2% chlorhexidine in 70% isopropyl alcohol.
●Strict maintenance of the asepsis while handling needles, guidewires, and catheters.
●Sutureless securement of the catheter to the skin.
Ultrasound machine — Clinicians should gain familiarity with the specific functions of the ultrasound machines in use at their institutions. The following are the typical steps involved:
●Turn on the ultrasound machine.
●Enter patient data.
●Choose the appropriate machine program examination, which is critical. The preset optimizes parameters such as velocity scale, which can impact image quality. The "peripheral vascular, venous" or "superficial vascular, venous" setting is usually the preferred option.
●Apply ultrasound gel to the transducer.
●Localize the vessel to be cannulated in the transverse and/or longitudinal plane and ensure proper orientation of the probe position marker depending upon the view and vascular access site. (See 'Ultrasound views' above and 'Probe orientation' above.)
●Once the selected vein is in view, the operator can fine-tune the image. Modify the position of the patient or route of access depending upon the ultrasound findings. Adjust the image parameters, as needed, including:
•Gain, which refers to the brightness of the grayscale image, analogous to volume on a radio (image 4).
•Depth, which refers to the depth of tissue included in the field of view. An appropriate depth includes the vein to be cannulated and a small amount of deeper tissue (image 5).
•Time gain compensation, which refers to adjustment of brightness (gain) of reflected signals based on the amount of time that has passed since the signal was emitted from the probe. Typically, the ultrasound image gets darker with increasing depth due to gradual attenuation of reflected sound waves. This setting allows for targeted adjustments of the gain in the near-field, middle, and far-field sections of the screen to create a more uniform grayscale image (image 6).
•Focal zone, which refers to the depth level at which the sound waves will be most tightly focused and will produce the best image resolution. Position the focal zone at the level of the vein.
•Color and/or spectral Doppler, if needed. Color Doppler ultrasound can be turned on with a single button, and its parameters can be adjusted. If an appropriate preset is chosen, probably only the color gain will need to be adjusted. Spectral Doppler is also activated with a single button. The operator needs to steer the gate (the small cross-hatched area used to obtain the waveform) over the vessel by moving the trackball slowly back and forth, analogous to moving the cursor on a computer screen.
Probe — When using ultrasound for real-time monitoring during catheter placement (in contrast to localization and measurement prior to catheter placement), take steps to ensure the sterility of the ultrasound probe. Commercially available sterile long plastic sleeves are available for this purpose. Never use a sterile glove or a sterile plastic drape around the probe since these do not ensure asepsis . Operators should also be aware of the need to properly disinfect the ultrasound probe between patients and to always use sterile gel. For further details, see guidelines from the American Institute of Ultrasound in Medicine .
To prepare the probe for sterile use:
●Apply ultrasound gel to the head of the probe.
●Place the probe into the sterile sleeve.
●Force any air out. Air bubbles trapped in the probe cover leads to poor image quality.
●Secure the sterile cover with a sterile rubber band. A snug fit of the cover over the transducer is needed.
●Squeeze excess gel up the sleeve, above the rubber band.
●Apply additional sterile conductive medium (eg, sterile lubricant gel, saline) between the wrapped probe and the surface of the skin.
DYNAMIC ULTRASOUND TECHNIQUES — Dynamic ultrasound is always preferred to guide placement of central venous catheters or peripheral intravenous catheters. Static ultrasound as the only ultrasound technique should be discouraged. Identifying an appropriate vein, marking its position, and then attempting a "blind" landmark approach is inaccurate, unsafe, and not cost effective.
Dynamic ultrasound guidance allows for real-time needle visualization during puncture of the vessel, as well as guidewire passage and catheter advancement, which ultimately increases successful placement and minimizes complications. The operator must learn the bimanual technique of holding the probe in one hand (typically nondominant) to identify the target vein, advancing the needle with the other hand, and simultaneously keeping eyes on the ultrasound (US) monitor at all times. Bimanual technique can be quite challenging to learn and is often frustrating for beginners. Mastery requires adequate training and plenty of supervised practice. Use of phantoms or simulators is helpful for increasing operator skill and confidence prior to transitioning to actual patients.
An assistant is extremely helpful for adjusting US parameters, holding the patient's arm steady (such as with children), or passing supplies to the operator. However, a two-person technique with one person holding the probe and the other person holding the needle leads to confusion and should be discouraged.
Maintaining continuous visualization of the needle tip is difficult, but critical for success. Techniques that are helpful for needle tip visualization include optimizing ultrasound settings (see 'Ultrasound machine' above) and using an echogenic needle [4,109,110]. "Sweeping" or "rocking" the US probe over the needle tip so that the needle tip "flashes" in and out on the screen is helpful for distinguishing the needle tip from the shaft. As the needle is advanced toward the target vein, the probe will also need to be advanced in sync with the needle to maintain continuous visualization of the tip. Temporarily angling or tilting the needle so that it has a more horizontal orientation increases sound wave reflection (echoes) and improves visualization of the needle (image 7).
Vein cannulation — Once the vein site has been prepared and draped, the following steps should be performed in sequence for dynamic ultrasound-guided venous access.
●Center the target vein on the ultrasound screen (transverse view) (picture 2), or obtain a longitudinal view using care to distinguish veins from arteries (image 1 and image 2). (See 'Ultrasound evaluation of vessels' above and 'Probe orientation' above.)
●Anesthetize the puncture site (eg, 1% lidocaine, 0.75% ropivacaine) using ultrasound, which is always recommended. Ultrasound-guided local anesthesia administration helps prevent inadvertent puncture of the artery or vein, or excessive administration that might distort the anatomy.
●For central line placement (centrally inserted or peripherally inserted), use of a 21-gauge needle (rather than an 18-gauge needle) with an 0.018 inch guidewire is always recommended. The smaller needle allows for easier and safer puncture of the target vessel, especially small or low-pressure veins. This may require the use of a micropuncture set to upsize to a larger guidewire (0.025 or 0.035 in).
●After the puncture site is anesthetized, insert the needle and advance slowly either in plane or out of plane. If identification of the needle tip is difficult, do not move the needle; rather, move the probe to find the needle and redirect it properly.
It is important to focus on the tip of the needle rather than the needle shaft, which can be facilitated by "rocking" the probe back and forth so the tip "flashes" in and out on the screen. When using the out-of-plane technique, failure to adequately identify the tip of the needle may allow it to advance to a deeper level than is desired, which can lead to inadvertent injury. The needle should not be advanced deeper into tissue unless the needle tip is definitively visualized.
●The needle must be slowly advanced toward the vein, under ultrasound control. This might be easier with the in-plane technique rather than out-of-plane. The needle should be aimed for the "12 o'clock" position of the vein (as seen in the short-axis). Whether using the "in-plane" or "out-of-plane" technique, look for indentation or flattening of the top wall of the vein as confirmation for an optimal puncture site (image 8).
Blood return may be noted at the hub when the needle punctures the venous endothelium, especially if there is a tourniquet applied or elevated central venous pressure. However, blood return may not always be seen in low pressure veins, in which case gentle aspiration with a syringe can be performed for confirmation. Alternatively, ultrasound can be relied upon to confirm that the needle tip is intravascular. If using the "in-plane" technique, slow passage of the guidewire into the vein without resistance can be visualized and confirms satisfactory intravascular position. If the guidewire does not easily pass, needle repositioning or advancement will be needed. Extreme care should be taken if the guidewire is retracted back into a needle as the tip of the guidewire can be easily sheared off and retained in the patient. If the slightest resistance to retraction of the guidewire is detected, the wire and needle should be removed together.
●Once the vein has been accessed, set the transducer down on the sterile field in case it will be needed again, and place the catheter using standard techniques. (See "Placement of jugular venous catheters" and "Placement of subclavian venous catheters" and "Placement of femoral venous catheters" and "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies".)
Post-cannulation ultrasound — Depending on the type of device and on the venous approach, ultrasound may be useful after the procedure for different maneuvers to:
●Assess the presence of tissue hematomas and/or intramural hematomas, particularly after a difficult puncture with repeat needle passes.
●Control the direction and progression of the catheter or of the guidewire using supraclavicular ultrasound (particularly during peripherally inserted central catheter [PICC] insertion) or after an infraclavicular approach .
●Verify the presence of the pleural "sliding sign" in the intercostal space to rule out pneumothorax (particularly after axillary or subclavian venipuncture). Ultrasound can be more sensitive than a chest radiograph for detection of pleural injury and pneumothorax [16,17]. (See "Central venous access: General principles", section on 'Confirming catheter tip position'.)
●Locate the tip by echocardiography, which is particularly easy and accurate in neonates and in infants but feasible also in adult patients [5,100]. (See "Central venous access: General principles", section on 'Confirming catheter tip position'.)
PITFALLS AND COMPLICATIONS — No complications unique to ultrasound-guided vascular access have been reported. The risk of complications inherent in vascular access such as hematoma, inadvertent puncture of nearby vessels or nerves, or unsuccessful cannulation is significantly reduced with the use of ultrasound guidance . In addition, ultrasound guidance shortens the time to successful cannulation and reduces the costs of the procedure. (See "Overview of complications of central venous catheters and their prevention in adults" and 'Supraclavicular venous access' above.)
Incorrect use of the ultrasound machine can make it difficult to identify vascular structures. A common pitfall is applying too much pressure with the transducer, thus collapsing the vein and rendering it invisible. Another problem is using incorrect settings on the ultrasound machine.
The main cause of adverse events during ultrasound-guided venipuncture is poor training of the operator. The pivotal role of training cannot be overemphasized [4,111-114]. Self-training and inappropriate/insufficient training are both associated with gross errors in the puncture technique and puncture-related complications. It is highly recommended that the clinicians who insert central venous access device be properly trained according to the recommendations of the World Conference on Vascular Access (WoCoVA) consensus, an evidence-based document that has analyzed the most appropriate training strategy for teaching ultrasound-guided venous access .
ADDITIONAL RESOURCES — High-quality instructional videos of ultrasound-guided internal jugular and peripheral vein access are available elsewhere [115,116].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Venous access".)
SUMMARY AND RECOMMENDATIONS
●Global use of ultrasound – The global use of ultrasound, which includes access planning, guiding insertion, and identifying complications, can be applied to placement of central venous catheters and peripheral intravenous lines. In adult and pediatric populations, ultrasound equipment and expertise using it should be available whenever venous access is needed. (See 'Introduction' above and 'Access sites' above.)
●Ultrasound techniques – Dynamic ultrasound guidance is the technique of choice during venipuncture. Using "static" ultrasound localization of the vein with a subsequent "blind" venipuncture technique is discouraged. The key anatomic aspects, preparation, and necessary steps to successfully perform ultrasound-guided venous access are described above. (See 'Ultrasound evaluation of vessels' above and 'Preparation' above and 'Dynamic ultrasound techniques' above.)
●Ultrasound for central venous access – The use of ultrasound reduces the risk of complications inherent in central vascular access. In addition, ultrasound guidance shortens the time to successful cannulation and reduces overall costs. (See 'Recommendations' above and 'Use of ultrasound and efficacy at specific sites' above.)
•Jugular venous access – For children and adults undergoing internal jugular access, we recommend that the procedure is guided by ultrasonography rather than using a landmark technique (Grade 1A). Studies support a similar benefit for ultrasound when accessing other supraclavicular veins. (See 'Internal jugular' above.)
•Infraclavicular access – For children and adults undergoing infraclavicular (subclavian, axillary) access, we recommend that the procedure is guided by ultrasonography rather than using a landmark technique (Grade 1B). (See 'Infraclavicular venous access' above.)
•Femoral access – For children and adults undergoing femoral access, we recommend that the procedure is guided by ultrasonography rather than using a landmark technique (Grade 1B). (See 'Femoral veins' above.)
•Emergency access – Ultrasound-guided access should not supplant emergency access including central venous or intraosseous access in a life-threatening situation when peripheral intravenous access is not rapidly successful. If an emergency landmark-based femoral venous catheter has been placed, it should be removed within 24 to 48 hours and replaced by an ultrasound-guided central venous catheter. (See 'Contraindications and precautions' above.)
●Peripheral intravenous access – Ultrasound guidance is also helpful for establishing peripheral intravenous access in children and adults when difficult intravenous access (DIVA) is expected or when prior attempts using standard (landmark) techniques have failed (no peripheral access after three attempts by an experienced clinician). For children with DIVA, we suggest ultrasound guidance as the initial approach, rather than using standard techniques (Grade 2C). Ultrasound has no role in peripheral venous access in neonates; near-infrared imaging may be useful. (See 'Peripheral intravenous devices' above.)
ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Lauren Averill, MD, Erica Mitchell, MD, FACS, and Mauro Pittiruti, MD, who contributed to earlier versions of this topic review.