Ultrasonography-Assisted Central Line Placement (Central Venous Access)

Central venous (CV) access is a commonly performed procedure with multiple indications in routine and emergent situations. Access to the internal jugular vein (IJV), ^[1]  the subclavian vein (SV), ^[2] and the femoral vein (FV) using the traditional landmark-based approach has typically been described in emergency medicine and critical care literature. Central venous access devices are routinely used in clinical practice for administering fluids and medications, for drawing blood samples, and for providing hemodynamic monitoring. The adoption of ultrasound-guided venipuncture has significantly reduced procedure-related complications. Bedside ultrasound has come to be regarded as a promising tool for ensuring an accurate and intraprocedural method of tip navigation and tip location. ^{[3, 4]}

The American Society of Anesthesiologists (ASA) has published guidelines on central venous access, including the following ^[5] :

• Use real-time ultrasound guidance for vessel localization and venipuncture when the internal jugular vein is selected for cannulation. When feasible, real-time ultrasound may be used when the subclavian or femoral vein is selected.
• Use static ultrasound imaging before prepping and draping for prepuncture identification of anatomy to determine vessel localization and patency when the internal jugular vein is selected for cannulation. Static ultrasound may also be used when the subclavian or femoral vein is selected.

Over 5 million central lines are placed in the United States each year. In the past, anatomic landmarks have been used  for placement of central lines, and in some instances this approach is still used. However, this method may make accessing the target vessel difficult in patients with anomalous anatomy or in obese patients, often decreasing the chance for successful placement and increasing the risk of complications. The use of ultrasound during central venous access has been shown to decrease both complication rates and costs. ^[6]

Studies using landmark-based methods have reported failure rates and complication rates as high as 30% ^[7] and 18.8%, respectively. One study looked at femoral venous access during cardiopulmonary resuscitation (CPR) and found that 31% of catheters were not in the femoral vein. ^[8]

Use of ultrasonography for CV access was first described in 1978 ^[9] ; Doppler localization was used to mark the skin overlying the IJV. Not until 1986 was the use of real-time ultrasonographic guidance for IJV cannulation reported. ^[10]  An Agency for Healthcare Research and Quality Evidence Report listed bedside ultrasonography during CV access as one of 11 practices with "strength of evidence for supporting more widespread implementation." ^[11] In the Emergency Ultrasound Guidelines from the American College of Emergency Physicians (ACEP), ultrasonographic guidance for CV access was listed as a "core or primary emergency ultrasound application." ^[12]  Ortega et al described the method of employing ultrasonography for locating the IJV, underlining the safety and reliability of this technique. ^[13] These authors also detailed intraoperative use of sterile ultrasonography.

When inserting a central venous catheter, one should consider appropriate preparation and asepsis, proper positioning of the patient, and optimal use of ultrasound. Compared with the landmark method of localization, ultrasound can account for anatomic variations, while facilitating visualization of venous puncture and safeguarding against inadvertent arterial puncture. ^[14]

Guidelines and practical advice for ultrasound-guided CV access have been published by the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB). They recommend real-time ultrasound (RTUS) for central venous access as a key safety measure, as well as for use in detecting complications of vascular access and treatment of arterial pseudoaneurysms. ^{[15, 16]}

The EFSUMB suggests the following steps for avoiding risks and complications ^{[15, 16]} :

• Check the equipment and its function during preparation.
• Optimize the B-mode picture of the target vessel.
• Optimize positioning of the patient (eg, Trendelenburg position), of the examiner, and of the US device relative to the puncture site (aim for a comfortable working environment for the interventionalist).
• Choose the most appropriate head position to locate the target vein lateral rather than anterior to the artery.
• Complete skills training on appropriate phantoms and on normal patient conditions before participating in emergency situations.
• For hypovolemic patients, provide intravenous fluid before performing the puncture.
• Carefully consider the indication for central lines—sometimes peripheral vascular access will meet the needs of the condition.

A prospective cohort study by Ullman regarding the rate and causes of central venous access device (CVAD) failure and complications in 163 pediatric patients found that CVAD failure occurred in 20% of devices (incidence rate [IR], 5.72 per 1000 catheter days). CVAD complications were evident in 43% of all CVADs (IR, 12.29 per 1000 catheter days). Causes of failure and complications included inconsistent use of ultrasound guidance for insertion, suboptimal tip-positioning, and device selection. ^[17]

Central venous access devices are often needed in neonates admitted to the neonatal intensive care unit. The location of the tip of the central catheter is usually assessed by postprocedural x-ray. Guidelines strongly recommend intraprocedural methods of tip location to increase the cost-effectiveness of the maneuver and to shorten the time between device placement and utilization. In this regard, real-time ultrasound represents the most promising tool for tip navigation and location in neonates. ^[18]

Use of ultrasonographic guidance during CV line placement has been shown to significantly decrease the failure rate, the complication rate, and the number of attempts required for successful access. ^{[19, 20, 21, 22]} A randomized, multicenter trial using point-of-care limited ultrasonography assistance in CV cannulation reported that ultrasonographic guidance resulted in an odds improvement 53.5 (6.6-440) times higher than the landmark-based technique for success of cannulation. ^[23] The average number of attempts and the average time to cannula placement were also significantly lower in the ultrasonographically guided group.

Ultrasonographic guidance can facilitate establishment of CV access from multiple sites. ^[24] Ultrasonographic guidance is most useful for cannulation of the IJV and the FV. ^{[25, 26]} Beaudoin et al found anatomic variability of the femoral vasculature where landmark-based FV cannulation is often attempted. They suggested that ultrasound guidance would improve cannulation and reduce complications during the procedure. ^[27] A prospective trial of ultrasound-guided femoral CV access reported a trend toward a decreased rate of complications. ^[28]

Access to the SV is more difficult because of its deeper location and the presence of the overlying clavicle, which can prevent the transmission of ultrasound waves. However, ultrasonographic guidance at the midpoint of the clavicle, using the long-axis approach, has been described, as has the supraclavicular approach. An observational study by Theodoro et al suggested that using ultrasonographic guidance to cannulate the IJV may result in fewer adverse events than occur with a landmark-guided approach to the SV. ^[29]

Additionally, infraclavicular axillary vein cannulation, performed a few centimeters lateral but otherwise in a similar fashion to the infraclavicular approach to the SV, can be performed using either long-axis or short-axis ultrasound. An ultrasound phantom-based study of this approach found that the long-axis approach was associated with greater first attempt success and fewer arterial punctures. ^[30]

Central venous access is indicated in the following cases:

• Other peripheral sites are unavailable or inaccessible.

• A large-bore venous catheter is needed for rapid administration of fluid or blood products in emergent situations.

• A CV catheter is needed for infusion of vasopressors, sclerosing agents, or hyperalimentation fluids with less risk to the vein.

• CV access is needed for placement of a pulmonary artery catheter or a transvenous pacemaker or for performance of hemodialysis or plasmapheresis.

• CV access is needed for continuous CV pressure and CV oxygen saturation monitoring during resuscitation.

Site-dependent contraindications

Site-dependent contraindications include the following:

• IJV or SV access in severely coagulopathic individuals for whom femoral access is preferred (SV and IJV cannulation in severely coagulopathic patients poses risk because of its noncompressible nature and the risk of accidental carotid puncture, respectively. For such patients, the femoral vein approach is preferred)

• Local infection over the intended site

Patient-dependent contraindications

Patient-dependent contraindications include the following:

• Inability of the patient to tolerate supine positioning

• Lack of patient cooperation

• Morbid obesity of the patient

Mechanical contraindications

Mechanical contraindications include the following:

• Contralateral pneumothorax or hemothorax

• Inability of the patient to tolerate ipsilateral pneumothorax

• Venous thrombosis

• Current or prior vessel injury

• High-pressure ventilator settings

• Trauma patient with cervical spine collar in place (IJV access is prohibited by placement of a cervical spine collar)

• Presence of Greenfield or IVC filter in FV cannulation (potential exists to snag the filter with the central line guidewire)

Most of the above-mentioned contraindications are relative, especially in the case of emergent access. Additionally, the use of ultrasonography has been demonstrated in numerous studies to reduce the rate of complications. A meta-analysis revealed that the relative risk of complications decreased by 57% when ultrasonography was used. ^[31]

A high-frequency (6-10 MHz) linear transducer, as shown in the image below, may be used for CV access.

 

Some studies have described the use of an endocavitary transducer for a short-axis approach to the IJV. The benefit of using this probe is its small footprint. ^[32]

Alternative use of the curvilinear probe has been described but is limited by its large footprint and the lower-resolution images yielded by lower frequencies.

A sterile barrier is necessary for use during real-time, dynamic visualization. ^[33] Sterile transducer covers are commercially available, although sterile gloves can also be used as a barrier.

The use of mechanical guides has been described, although experienced operators may not need to use them. Mechanical guides are available in 2 forms: guides with a built-in needle slot on the transducer, and guides that may be fitted onto the transducer.

A commercially available central venous guidewire catheter kit or catheter-over-needle device is also required. The kit typically contains a triple-lumen catheter, a vessel dilator, a spring guidewire with insertion device, a thin-walled percutaneous entry needle, various gauge needles, various syringes, sterile drapes, a No. 11 blade scalpel, lidocaine, and silk suture.

For IJV and SV access, patients should be placed in a slight Trendelenburg position. The head should be in a neutral position (maximum head rotation of 30°). A randomized trial comparing neutral head position versus 45° neck rotation did not reveal any difference in the rate of complications. Venous access time for these groups was also similar. ^[34]

For femoral vein access, the patient should be placed in a neutral position.

For operator-assisted IJV ultrasonographic guidance, the operator should stand on the ipsilateral side of the patient. The procedure should be performed from the head of the bed, and the indicator of the probe should be kept pointing to the operator's left (this corresponds to the left side of the patient's body and is opposite our traditional orientation). For cannulation of the right IJV, this probe orientation ensures that vessel positions in the patient's neck (carotid to left, IJV to right) show the same orientation on the ultrasound display. The operator should have a clear view of the ultrasound image.

Begin the procedure with handwashing and universal precautions, including sterile gloves, gown, mask, cap, and protective eyewear.

Cleanse the patient’s skin with an antiseptic such as a povidone-iodine solution, chlorhexidine gluconate, hexachlorophene, or a combination of these.

Vascular cannulation may be accomplished with a catheter-over-needle device or via the catheter-over-guidewire technique, which is more commonly known as the Seldinger technique.

The vessel to be cannulated may be located by ultrasonography via several accepted variations, including the dynamic (real-time) method and the static (indirect) method, both of which are described below.

Dynamic (real-time) method

The dynamic method, shown below, is typically performed by a single operator, although it can be performed with the aid of an assistant.

A sterile sheath that is commercially available or a glove with transmission gel (any sterile gel/lubricant may be used) inside should be unrolled over the ultrasound probe.

Additional sterile transmission gel is then placed on the outside of the probe cover.

The probe is placed on the patient's skin, and the target vessel is identified.

The vein is identified through several techniques, including phasic respiratory pulsations, ease of compressibility, and increased filling via the Valsalva maneuver.

The vein to be cannulated is centered on the ultrasound screen.

Once the anticipated path of the needle is identified, the path can be anesthetized with lidocaine under ultrasonographic guidance. This anesthesia minimizes patient discomfort.

Next, the skin is punctured with a thin-walled percutaneous entry needle. One should not focus on the ultrasound monitor until the needle has entered into the skin. Focusing on the monitor before needle entry can lead to inadvertent needlesticks.

Visual focus is then directed to the ultrasound monitor, where the needle appears sonographically as an echogenic line with reverberation or ring-down artifact. Often, the needle is not directly visualized; however, tenting of each tissue plane can be appreciated.

(See the video below.)

In the short-axis view, one should scan back and forth with the probe over the needle to locate the needle tip. Often, a longitudinal view can help localize the needle tip.

After the needle is seen puncturing the vessel and a flash of blood is noted in the syringe, the ultrasound transducer may be set aside. The remainder of the procedure can be completed without ultrasonographic guidance.

Visualization of the guidewire using the longitudinal view within the target central vein verifies intravenous placement. This view minimizes the risk of puncture of the posterior vessel wall.

In the event that the location of the wire cannot be verified (eg, in cases in which back-wall puncture of the vessel is suspected), the guidewire can be partially withdrawn and the curvature of the distal "J" portion of the guidewire can be visualized within the target vessel.

After needle puncture of the vessel and guidewire placement, the entry needle is withdrawn, and the puncture site is enlarged with a No. 11 scalpel blade.

A dilator may then be used to facilitate placement of the catheter.

Venous blood return and easy flushing suggest accurate placement. Ultrasonography can also be used to visualize the catheter and its relative location to the vein.

After the catheter is in place, it is secured with simple interrupted sutures or staples.

Postprocedural chest radiography is necessary to confirm placement and to evaluate for complications such as pneumothorax. Bedside ultrasonography can also be used to help assess for possible pneumothorax. The absence of lung sliding is more than 90% reliable for identification of a pneumothorax. ^[35]

If cannulation is unsuccessful, chest radiographs must be obtained before repeated attempts are made on the contralateral side to rule out complications.

Static (indirect) method

The indirect method (see the image below) involves the least amount of ultrasonographic guidance.

The vessel is identified and is centered on the ultrasound screen.

A temporary mark is then placed on the skin to indicate where the needle is to be inserted. This mark can be made by indentation or with use of a sterile marker.

A second mark is then placed distal to this mark along the course of the vessel for use as a guide in directing the path of the needle.

Axis of visualization

Additional considerations in the use of ultrasonography for CV access include the axis of visualization. Reported approaches include short-axis, long-axis, and combined approaches. ^[1]

In the short-axis, or transverse, approach, shown below, the vessel is centered under the transducer. The needle is then inserted at a 45° angle, using the midpoint of the transducer as a reference site.

In the long-axis, or longitudinal, approach, shown below, the greatest anterior-posterior diameter of the target vessel is visualized. The needle is then inserted at a 30° angle along the axis of the transducer.

The "ski lift" approach to ultrasound-guided vascular access has been suggested to improve successful line placement. ^[36] The authors use the long-axis view to visualize the entire needle and vessel concurrently, which is purported to minimize puncture of the posterior wall, while facilitating placement.

Takeshita et al reported on the occurrence of posterior wall puncture in long-axis in-plane (N=49) and short-axis out-of-plane (N-48) approaches for ultrasound-guided central venous catheterization. Posterior wall puncture rates were 8.2% (4/49) and 39.6% (19/48) for the long-axis group and short-axis group, respectively. First-attempt success rates were 67.3% (33/49) in the long-axis group and 64.6% (31/48) in the short-axis group. Overall success rates within 20 minutes were 93.9% (46/49) in the long-axis group and 93.8% (45/48) in the short-axis group. ^[37]

Advantages of each method

The short-axis approach is useful for concomitant visualization, for avoidance of adjacent arteries, for cannulation of smaller peripheral veins, and for situations in which space is limited (eg, when the IJV is cannulated).

The long-axis approach enables better visualization of the advancing needle and threading of the guidewire, as well as avoidance of inadvertent puncture of the posterior vessel wall.

Wire-in-needle (WIN)

Stone et al have described a novel ultrasound-guided vascular access technique involving use of a needle preloaded with the guidewire without use of a syringe. ^[38]

The needle containing the tip of the guidewire is inserted via the long-axis technique under dynamic ultrasound guidance. After the tip of the needle is seen entering the vessel, the wire is advanced into the vessel.

Advantages of this technique include eliminating the risk of dislodging the needle tip when the syringe is removed from the needle, as in the classic Seldinger technique, and increased echogenicity of the needle containing the wire on ultrasound imaging. One potential complication of this technique is misidentification of the target vessel, resulting in inadvertent cannulation of the carotid artery, for example.

Threading the catheter into the inferior vena cava

In some clinical conditions, central venous access is preferably or necessarily achieved by threading the catheter into the inferior vena cava. This can be done not only by puncture of the common femoral vein at the groin, but also by puncture of the superficial femoral vein at the midthigh. Annnetta and associates confirmed that the ultrasound approach to the superficial femoral vein is a safe technique of central venous access and was not associated with risk of severe insertion-related complications, even in patients with low platelet count or a coagulation disorder. They noted that an exit site of the catheter at midthigh may offer advantages over an exit site in the inguinal area. ^[39]

Supraclavicular vs infraclavicular approach

Supraclavicular (SC) and infraclavicular (IC) approaches are used for central venous catheterization; both have benefits and limitations. Nazir and colleagues reported that the SC approach can be used as an alternative to the IC technique because of its low access time and high success rate. ^[40]

Ultrasonographic guidance of FV cannulation during CPR has revealed that chest compressions are associated with changes in venous diameter. This finding suggests that the pulsations appreciated during CPR are actually venous. ^[41]

When the landmark-based approach is used for FV cannulation during CPR, needle insertion medial to arterial pulsation may be misleading.

Ultrasonographic guidance may also be used for peripheral venous cannulation in patients who need intravenous access but have no visible or palpable veins.

Echogenic polymer–coated needles, as used during ultrasonographically guided biopsy and during ultrasonographically guided egg retrieval for in vitro fertilization, may be useful during central line placement because they allow enhanced visibility of the needle tip on ultrasound. ^[42]

CV access, in general, carries multiple potential complications, including the following:

• The most serious and most common complications include pneumothorax, arterial puncture and cannulation, and local infection.

• Less common complications include air embolism, subcutaneous and mediastinal hematoma, thrombosis, hydrothorax and hydromediastinum secondary to superior vena cava puncture or perforation, chylothorax, dysrhythmia, nerve injury, and catheter or guidewire embolism. ^[43]

• Potential complications during anesthesia administration include inadvertent venous or arterial infusion of lidocaine with or without epinephrine or subcutaneous air instillation that obstructs view during ultrasonographic guidance.

Studies have shown that ultrasonographically guided CV access decreases the associated complication rate by as much as 75%. Also, simulation-based ultrasound training helps inexperienced operators achieve greater successful central line placement rates with an improved safety profile. ^[44]

Patient Education and Consent

Consent should be obtained from the patient or from a family member, unless emergent circumstances dictate otherwise. ^[45] The patient should be told the reason the procedure is being performed (suspected diagnosis); risks, benefits, and alternatives of the procedure; risks and benefits of the alternative procedure; and risks and benefits of not undergoing the procedure. The patient should be given the opportunity to ask questions and to raise any concerns. The patient must have an understanding about the procedure that will enable an informed decision.

The patient should be counseled about risks of an allergic reaction to local anesthesia, vascular injury (air embolus, damage to adjacent vessels, pericardial tamponade, catheter embolus, arteriovenous fistula, mural thrombus formation, hematoma), infection (localized cellulitis, generalized sepsis, osteomyelitis), dysrhythmia, and catheter malposition. For subclavian and internal jugular approaches, the patient should be advised about risks of pneumothorax, hemothorax, chylothorax, hemomediastium, neck hematoma and tracheal obstruction, tracheal perforation, phrenic nerve injury, brachial plexus injury, and cerebral infarct. For the femoral approach, the patient should have risks of psoas abscess, bladder perforation, and femoral artery injury explained.

The patient should be reassured that use of ultrasound will help reduce many of these risks and will help guide the physician in locating the correct vessel.

The patient should also be counseled that even if there are no complications, the procedure may not be successful and a diagnosis still may not be obtained. One should discuss with the patient the possibility that the catheter may be placed in the wrong position and may need to be repositioned. Also the patient should be instructed that the procedure may need to be repeated.

Ways these risks can be avoided or prevented should be explained (eg, use of ultrasound, proper positioning, ensuring that the patient remains as still as possible during the procedure, adequate analgesia).

Anesthesia

Lidocaine with or without epinephrine may be infiltrated locally under ultrasonographic guidance. For more information, see Local Anesthetic Agents, Infiltrative Administration.

Instillation of anesthetic with ultrasonographic guidance allows more precise placement and improved analgesia.

Inadvertent air instillation in the overlying tissues is important to avoid, as this may cause reverberation or a free air artifact that obscures the ultrasound image.