ATS SEMINARS Intensive Care Ultrasound Series Editor: Gregory A. Schmidt, M.D.

II. Central Vascular Access and Venous Diagnostic Ultrasound Michael J. Silverberg1 and Pierre Kory1 1

Beth Israel Medical Center, Division of Pulmonary, Critical Care, and Sleep Medicine, New York, New York

Background The use of ultrasound imaging to guide the insertion of central venous catheters lies at the forefront of the revolution in point-of-care ultrasonography. Multiple studies have shown that real-time two-dimensional ultrasound guidance for internal jugular catheter insertion leads to significantly lower failure rates, both overall and on the first attempt (1–7). Benefits include faster insertion times and fewer complications such as pneumothorax and arterial cannulations (3, 6). Based on the number and strength of the above studies, the Accreditation Council for Graduate Medical Education has now mandated that training be provided in this skill. Multiple guidelines now recommend that all internal jugular central venous catheters (CVC) be placed with ultrasound guidance (8–11). Similarly, femoral CVC insertion has improved success with ultrasound guidance, and this should be used if time allows (5). Although subclavian vein CVC insertion is more technically difficult with ultrasound, and fewer studies have been performed with this approach, a significantly decreased rate of complications has been observed when performed by expert operators (12).

Internal Jugular Insertion Technique In the following sections, ultrasound-guided CVC insertion techniques are described using the internal jugular vein only, although these approaches can be applied to any

Figure 1. Machine positioning. Ultrasound machine placed directly beyond insertion site with screen facing operator, allowing for minimal head turning.

(Received in original form June 10, 2013; accepted in final form July 29, 2013 ) Correspondence and requests for reprints should be addressed to Pierre Kory, M.D., M.P.A., Beth Israel Medical Center, Division of Pulmonary, Critical Care, and Sleep Medicine, Dazian Building, 7th Floor, 16th Street and First Ave., New York, NY 10003. E-mail: [email protected] This article has an online supplement, which is accessible from this issue’s table of contents at www.atsjournals.org This article has associated videos, which are accessible online at www.atsjournals.org Ann Am Thorac Soc Vol 10, No 5, pp 549–556, Oct 2013 Copyright © 2013 by the American Thoracic Society DOI: 10.1513/AnnalsATS.201306-148OT Internet address: www.atsjournals.org

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ATS SEMINARS insertion site with only slight modifications. The use of Centers for Disease Control and Prevention–recommended full sterile precautions and time-out procedures is assumed and will not be fully detailed (13).

Machine Positioning The ultrasound screen must be positioned directly facing the operator, just beyond the insertion site, creating a direct line of sight (Figure 1). A common error leading to excess difficulty is to allow for a malpositioned machine that requires excessive turning of the operator’s head and torso. Care should be taken to set height of bed to maximize operator comfort. Awkward positioning leads to increased difficulty of needle and transducer (probe) control, potentially leading to complications and lower success rates.

Transducer Selection CVC insertion sites are all within several centimeters of the skin surface, so linear, high-frequency transducers should be used, given the high resolution they afford at shallow depths. Their linear design produces a rectangular screen image display allowing for enhanced visual-spatial feedback of needle movements (Figure 2).

Figure 2. Ultrasound transducers. Typical appearance of a high-frequency, linear transducer on the right with a lower-frequency, phased-array transducer on the left.

machine is positioned as above (i.e., directly facing the operator from just beyond the site of insertion). The screen orientation marker should be positioned in the upper left of the screen. With this orientation of the transducer and screen, hand movements will correspond with those on the screen, allowing for optimal guidance.

Depth and Gain Settings Before insertion, proper gain and depth should be set so that the anechoic (i.e., blood-filled vessels) and echoic (i.e., muscle, fat) structures are maximally resolved with clear identification of all tissue planes. The depth should be set so that the

Transducer Hold The transducer should be held with the thumb and index finger on both edges and the hypothenar eminence resting on the skin surface of the patient (Figures 3A and 3B). This grip will allow the operator to maintain a comfortable and stable position of the probe leading to a stable image of the target vessel during needle guidance. An unsupported transducer hand often leads to slippage during insertion, with loss of needle and target vein visualization.

Transducer and Screen Image Orientation To produce optimal visual-spatial orientation in ultrasound-guided CVC insertions, the probe marker should be oriented to the operator’s left when the 550

Figure 3. Transducer handling. (A) Recommended hand position to produce the most stable target vessel image throughout insertion. (B) Suboptimal hand stabilization leading to risks of target vessel movement during insertion.

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Figure 4. Effect of transducer angulation. (A) Artery lying directly below the vein. (B) Tilting of the transducer medially will result in an image with a safer access path.

vein appears perfectly centered on the screen, where image resolution is optimized.

Assessment of Internal Jugular Veins Before the sterile field is created, both internal jugular veins should be examined in both transverse and longitudinal orientations for course, size, and any evidence of thrombosis, avoiding sites of stenosis or suboptimal orientation to the carotid artery. In general, the right internal jugular vein should be the first choice unless vessel pathology or anatomy is unfavorable. A brief examination of the anterior thorax to confirm lung sliding before insertion is necessary to rule out the presence of a pneumothorax after the procedure.

Defining the Vascular Anatomy Normal veins are easily compressible under minimal pressure, exhibit respiratory variation, have walls of an imperceptible thickness, are larger than arteries, and are oval or teardrop in shape. In contrast, arteries do not compress under light pressure; have thicker, echogenic walls; and are almost perfectly round in shape, while exhibiting pulsations (Video 1). In pathologic states, these characteristics are sometimes lost; for example, veins can be ATS Seminars

pulsatile in elevated pulmonary pressure states, noncompressible when thrombosed, or stenotic (i.e., smaller than arteries). If the nature of a vessel is uncertain, color or spectral Doppler may be useful. The color flow in a vein can be augmented by compressing distal to the vessel, whereas the arterial flow will remain unchanged.

Sterile Preparation of Transducer Once the insertion site and patient have been prepared and draped using sterile technique following both institutional policy and accepted guidelines, a sterile probe sleeve should be opened and dropped onto the sterile field. When placing the transducer sleeve, sterility must be maintained to the outer surface of the sleeve, the field, and the operator’s gloves. Sufficient gel should be inserted into the sleeve to cover the face of the transducer. The sleeve must be tight against probe face so that only gel is interposed. A clip or band should be used to maintain a tight sleeve fit.

Selection of Target Site Imaging should start with the traditional “landmark” site at the apex of the triangle

formed by the two heads of the sternocleidomastoid muscle. A safe site is one where the carotid artery is lateral to the jugular vein. If the artery lies directly beneath the vein on the screen, two maneuvers can be used to correct this: (1) “roll” or angle the transducer laterally or medially to produce an imaging plane and needle insertion angle where artery is not deep to vein, or (2) slide the transducer proximally or distally following the course of the artery and vein to a point where the artery lies lateral (Figures 4A and 4B, Videos 2A and 2B).

Needle Guidance Techniques Real-time guidance of needle insertion is superior to approaches that use ultrasound site marking followed by needle insertion (14). Multiple techniques have been used to perform real-time guidance of needle insertion. No single technique is mandated; however, the optimal approach should rely on the ability to visualize the needle tip throughout insertion as opposed to some undefined point of the needle shaft. Such needle-tip visualization techniques, although technically more challenging, will more definitively avoid erroneous arterial or lung punctures from excessive depth of insertion. A description of the various techniques follows. 551

ATS SEMINARS as revealed on the screen. Advance the transducer and needle tip in tandem, with the needle at a 45-degree angle and keeping the transducer directly over the needle tip throughout insertion (Video 5). The risk of complications is increased if the transducer is not kept aligned over the needle tip. Tilting Transducer Technique

This method is similar to the sliding transducer technique, but the transducer is angled, rather than advanced, to keep the tip within the imaging plane throughout insertion. For internal jugular vein cannulation, often only minor angling is required (Videos 6A and 6B). In-Plane Technique

Orient the transducer along the longitudinal axis of the vein. Insert the needle tip at the center of the end of the transducer and visualize the needle tip. Advance the needle at a 45-degree angle while keeping the needle within the imaging plane of the transducer. Although visualization and safety are optimized with this approach, it can be challenging to hold the transducer directly over the vein without slipping. This technique can also be challenging in patients with a short neck, especially when using wider probes (Videos 7A and 7B). Figure 5. Venous anatomy of the left lower extremity. The numbered points denote the minimum sites of compression for a limited examination. Note the paired common femoral artery, which divides proximal to the division of the common femoral vein (CFV), producing several cross-sectional segments of the CFV showing two adjacent arterial branches, the superficial femoral artery and the deep femoral artery. a = artery; v = vein.

Triangulation Technique

Place the transducer transversely over the vein, keeping the vein well centered and the transducer immobile. Estimate the depth from probe face to front wall of the vein. Insert the needle an equal distance proximal to the transducer, at a 45-degree angle in the center axis of the transducer. The danger of this technique is that the needle tip is not visualized throughout insertion and can puncture lung or artery (Videos 3A and 3B). The use of needle guides to execute this approach may be more successful for novice users (15, 16). Near-Vertical Technique

Using the transverse view, place the needle directly against the center point of the 552

transducer and insert at a near–90-degree angle to the vein in an attempt to bring the needle tip within the imaging plane of the transducer. Risks are similar to the triangulation technique, because the needle tip is still not visualized continuously throughout insertion. After entering the vein, reduce the needle angle to facilitate wire insertion (Videos 4A and 4B).

Medial Transverse In-Plane Technique

In this method, the operator stands on the side of the patient opposite from the vessel. Orient the transducer transversely over the vein, place the needle at the center of the medial end of the transducer, and insert the needle in the plane of the transducer, taking care to use an angle that allows the needle to pass superficially to the artery and into vein. Once blood is returned, point the needle tip toward the heart to facilitate advancing the wire (Videos 8A and 8B) (17).

Confirmation of Wire Placement Sliding Transducer Technique

Place the transducer transversely over the vein and estimate depth to the front wall. Insert the needle an equal distance away from the transducer. Then slide the transducer directly over the needle tip,

One of the most important applications of ultrasound in CVC insertion is the ability to confirm placement of the wire within the vein before dilation of the vessel, avoiding the serious risks associated with carotid

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Figure 6. Patient positioning for lower extremity venous examination. Note the machine positioned just beyond the examination site with the screen facing the operator. The patient’s leg is externally rotated to expose the groin region.

artery injury (18). To confirm wire placement, a longitudinal orientation is required to ensure that the wire stays within the vein distally (Video 9). Once the wire location is confirmed, vessel dilation and catheter insertion can safely proceed. After the procedure is completed, the anterior chest should again be assessed for lung sliding (Video 10). If there was lung sliding before the procedure and no lung sliding post procedure, pneumothorax must be ruled out immediately.

Compression Ultrasonography for the Detection of Deep Venous Thrombosis Introduction

An important and related skill to ultrasound-guided CVC insertion is the performance of a compression ultrasound examination to diagnose deep venous thrombosis (DVT). Beyond the need to choose an insertion site free of thrombus, prompt identification of DVT is often desired when clinicians are challenged with

diagnosing the causes of new or worsening shock states or hypoxemia. Fortunately, compression ultrasound examinations have been shown to be of equal accuracy to traditional multimodality examinations performed by radiology or vascular laboratories (i.e., “duplex” and “triplex” examinations that use color and spectral Doppler, respectively) (19–27). Other benefits include avoiding the need for patient transport, radiation exposure, intravenous contrast, and the oftentimes lengthy delays in the receipt of an interpreted examination performed by radiology and vascular laboratories that rarely provide 24-hour availability (27). This emphasizes the value of compression ultrasound examinations in the skill set of the front-line intensivist, supported by studies showing high accuracy of clinicians after focused training (21, 25, 27–30). Proximal Versus Distal Lower Extremity DVT

In the following sections, we focus solely on the performance of compression ultrasound examinations for proximal lower extremity DVT (popliteal and femoral veins), avoiding a discussion of calf DVT for several reasons. First, calf DVTs have only a 10% risk of embolizing if left untreated, typically extending proximally before doing so; and second, ultrasound examinations of the calf veins have far less accuracy even for experienced operators (19, 31–35).

Figure 7. Normal compression. (A) Uncompressed common femoral vein. (B) Disappearance of venous lumen during compression (white arrow).

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ATS SEMINARS thrombus is identified, to then interrogate the entire length of the femoral vein down to the adductor canal. Indications

In the critically ill, a compression ultrasound examination is typically performed in patients with (1) signs or symptoms of pulmonary embolism or DVT, (2) undifferentiated shock or hypoxemia, or (3) newly discovered or unexpected right ventricular dysfunction.

Proximal Lower Extremity Anatomy

Figure 8. Patient positioning for popliteal vein compression. Note the leg elevated off the bed and flexed to 45 degrees allowing for transducer to be placed behind popliteal fossa.

Complete Versus Limited Examination

A related clinical question is whether a “complete” examination of the proximal lower extremity, which includes the entire extent of the femoral vein, or a “limited,” two-site examination is sufficient (one that solely examines the common femoral vein branch points and the popliteal vein). Studies show that in patients with

localizing signs or symptoms to an extremity, a limited examination is highly sensitive and specific (36–38). In the absence of localizing findings where the clinician is searching for the presence of DVT, a complete examination is recommended, because 8 to 22% of DVTs are located outside the limited examination sites (27, 39, 40). A time-saving technique is to first perform a limited scan and, if no

A detailed knowledge of the deep femoral venous and arterial anatomy is required (Figure 5). The novice operator should be able to scan from the inguinal ligament to the popliteal vein and identify all branch points as follows: Just distal to the inguinal ligament, the common femoral vein and common femoral artery are seen. Notice that the artery splits into superficial and deep branches before the vein does, oftentimes showing two arteries adjacent to one large vein. After the common femoral artery splits, the greater saphenous vein enters the common femoral vein superomedially followed by the appearance of lateral perforator veins over the next 1 to 2 cm, ending with the split of the common femoral vein into the deep femoral vein posteriorly, after which the visualized vein is called the femoral vein (formerly the superficial femoral vein (Video 11). The deep femoral vein can usually be tracked for a short distance before it dives deeper and away from the acoustic window. The femoral vein runs anteromedially to the adductor canal, where it courses posteriorly into the popliteal fossa, becoming the popliteal vein (Video 11).

Patient and Equipment Set-Up

Figure 9. Popliteal vein, transverse view. Sonographic appearance of the popliteal vein superficial to the popliteal artery. Care must be taken to use light pressure when scanning to avoid disappearance of vein.

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The supine patient should have the lower extremity fully exposed and externally rotated. Similar to CVC insertion, a linear, high-frequency transducer with a frequency between 5.0 and 10.0 MHz is used. The machine should be distal (“downstream”) to the examination site, with the screen and control panel directly

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Pitfalls of Lower Extremity Venous Sonography d

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Figure 10. Lymph node. Normal sonographic appearance of a lymph node. Although not compressible, it should not be mistaken for a thrombosed vessel, given that it cannot be followed proximally or distally (disappears) and there is no paired vessel adjacent.

facing the operator (Figure 6). The transducer marker should be pointed to the patient’s right (operator’s left). Once the vessel is identified, depth is decreased so that the vessel is at the center of the screen, with the gain set so as to maximally resolve all soft tissue and vascular structures.

Compression Ultrasound Examination Patent veins are fully compressible under light pressure applied with the transducer, with the visible lumen completely disappearing as the opposing venous walls come into full contact (Figures 7A and 7B, Video 12). The inability to completely compress the venous lumen is thus the main criterion for the diagnosis of DVT (24). The amount of pressure required has to be lower than the pressure required to collapse the artery. If the vein is not collapsible at this pressure, this signifies that a thrombus is present. Common Femoral Vein

Compressions should begin above the inguinal ligament at the most proximal

visualizable portion of the external iliac vein. The operator should then compress every 1 to 2 cm, crossing the inguinal ligament to the proximal common femoral vein, the superomedial entrance of the greater saphenous vein, then over the lateral perforator-common femoral vein junctions, ending at the branch of the common femoral–deep femoral vein in a limited, “two-site” examination (Figure 1, numbered sites). For a complete lower extremity examination, the femoral vein is then compressed to its distal visualizable extent. Popliteal Vein

The knee is flexed approximately 45 degrees and externally rotated, with the transducer placed transversely over the mid-fossa (Figure 8). The paired popliteal artery and vein are located in a central position, with vein typically overlying the artery (Figure 9, Video 13). This orientation can make it difficult to identify the vein, given that even light transducer pressure can obliterate the venous lumen. Compressions are performed sequentially to a point just

References 1 Abboud PA, Kendall JL. Ultrasound guidance for vascular access. Emerg Med Clin North Am 2004;22:749–773. 2 Cajozzo M, Quintini G, Cocchiera G, Greco G, Vaglica R, Pezzano G, Barbera V, Modica G. Comparison of central venous catheterization

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Internal echoes (“smoke”) are frequently encountered in patent veins in the presence of low-flow states. These should not be confused with true thrombi. The novice sonographer will sometimes mistake other structures, such as a lymph node (hyperechoic center, hypoechoic rim) or muscle band (rounded, well circumscribed, linear internal echoes), for a thrombosed vein (Figure 10). The ultrasound appearance of a DVT changes over time: thrombi become progressively more echogenic as they organize, and the underlying venous wall in the area of thrombosis gets thicker, more echogenic, and resistant to compression. In cases of uncertainly, the novice sonographer should consider consultation with an experienced sonographer. Although risks of dislodging thrombus are considered minimal, we perform longitudinal scanning before compressing the vein to further minimize risk. Sonography is undoubtedly operator dependent. Fortunately, this skill has a steep learning curve and is relatively easy to perform.

Conclusions Bedside ultrasound in the intensive care unit is increasingly being used. Vascular access and DVT ultrasound are skills that can be acquired by critical care practitioners. Such skills are increasingly being taught as part of fellowship curriculum, with proficiency demonstrated after focused training. n Author disclosures are available with the text of this article at www.atsjournals.org.

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AnnalsATS Volume 10 Number 5 | October 2013

Intensive care ultrasound: II. Central vascular access and venous diagnostic ultrasound.

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