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Rajesh Geria, M.D., RDMS, Beatrice Hoffmann, M.D., Ph.D., RDMS

Ultrasound guided Vascular Access

I.  Introduction and Indications

Emergency physicians are often called upon to rapidly establish intravenous access for critically ill patients.  Depending on the clinical scenario, cannulation of a peripheral vein is first attempted and if unsuccessful, a more central vein is tried.  Several factors including body habitus, volume depletion and history of intravenous drug abuse can make this a challenging task.  

Bedside ultrasound not only provides us with a window of the patient’s vascular anatomy, but also gives us the ability to visualize the needle as it enters the body.  If used correctly, the needle can be successfully guided into the desired vein.  The use of ultrasound increases accuracy, limits complications and reduces the number of attempts of venous access. (1-5)

Indications:

• Real-time visualization and anatomical guidance of venous cannulation
• Minimize number of attempts
• Decrease complication rates

II.  Anatomy

It is important to appreciate the sonographic difference between veins and arteries.  Veins are thin walled, non-pulsatile, easily compressible, and in a patient with normal hydration status larger than arteries (Figure 1).  This principle applies to both the central and peripheral vasculature.  In this section we will discuss the basic anatomical landmarks required to perform peripheral and central venous cannulation.

Central Veins
When deciding which central vein to cannulate, we usually think of either the subclavian or internal jugular vein. The femoral vein should only be considered if the above veins are not accessible. As already hinted by its name, the subclavian vein runs for a significant distance under the clavicle. Ultrasound visualization in this area is extremely difficult, as the high acoustic impedance of the clavicle bone causes a large acoustic shadow in most areas of the image. Only in a very lateral or supraclavicular approach imaging can be obtained. This makes it a more difficult choice for cannulation under ultrasound guidance. In contrary, the internal jugular vein traverses the neck virtually unopposed by bone making it an ideal vessel to evaluate using ultrasound. The internal jugular vein runs vertically in the neck lying at first lateral to the internal carotid artery, and then lateral to the common carotid as it eventually unites with the subclavian vein. The internal jugular vein lies underneath the bifurcation of the sternal and clavicular heads of the sternocleidomastoid muscle (SCM), which is used as an external landmark when trying to locate the vein.

The common femoral vein is formed by the superficial femoral vein and the deep femoral vein approximately 5-7 cm caudal to the inguinal ligament. It is joined by the greater saphenous vein (a superficial vein) from medial prior to passing under the inguinal ligament to form the external iliac vein.
The common femoral vein lies medial to the artery only in the region immediately inferior to the inguinal ligament. It quickly takes a location posterior to the artery within 2 - 4 cm of the inguinal crease and remains posterior to the arteries into the calf (see also DVT chapter).

 

Figure 1:  Still image of left internal jugular vein in transverse view.

Peripheral Veins
The antecubital veins of the arm are most commonly used in the emergency setting (Figure 2). Superficial veins that traverse the antecubital fossa include the cephalic and basilic veins.  The cephalic vein begins in the radial part of the dorsal venous network and ascends upward within the superficial fascia in front of the elbow in the groove between the brachioradialis and biceps brachii.  The basilic vein begins in the ulnar part of the dorsal venous network.  It runs up the posterior surface of the ulnar side within the superficial fascia of the forearm in the groove between the biceps brachii and pronator teres.  The brachial veins begin at the elbow, by the union of the venae comitantes of the ulnar and radial arteries and lie deep to the superficial veins mentioned above.  The deep brachial vein lies adjacent to the pulsatile non-compressible brachial artery. 

Another common site for peripheral venous access is the external jugular vein (v. jugularis externa).  It receives blood from the exterior of the cranium and the deep parts of the face and is being formed by the posterior facial and auricular vein. The v. jugularis externa runs perpendicularly down the neck, in the direction from the angle of the mandible to the middle of the clavicle at the posterior border of the sternocleidomastoideus muscle. In its course it crosses the sternocleidomastoideus muscle obliquely, perforates the deep fascia in the subclavian triangle and ends in the subclavian vein,. The external jugular vein varies in size and is occasionally duplicated.

Figure 2:  Still image of a peripheral vein.

III.  Scanning Technique, Normal Findings and Common Variants

When attempting to localize these vessels on the ultrasound machine it is important to remember that superficial vessels stand alone while deeper vessels are paired.

Procedure Technique:
A linear array transducer with frequency ranging from 7.5 to 10 MHz is recommended for ultrasound guided vascular access.  Care must be taken to cover the probe with a sterile sheath prior to starting the procedure (Figure 3). The depth, direction and patency of the central or peripheral vein should be examined using ultrasound prior to needle insertion.  A proper “time-out” procedure step should be assured when necessary.

Figure 3:  Linear probe with sterile sheath cover.

Central Venous Access
Internal Jugular Vein (IJV)
The patient is prepped as if you would attempt a traditional line placement.

The patient’s head can be placed in the conventional rotated position or kept in a neutral head position.
A potential benefit of a neutral head position is that the internal jugular vein assumes a more lateral position to the carotid artery (it would rotate anterior and over the artery with head movement to the opposite side). Keeping the two major neck vessels in a parallel rather than perpendicular alignment can minimize the risk of arterial puncture should the needle be advanced too far. This is especially important in patients with low venous filling pressures and vein collapse.
Ultrasound should also be used to locate the sternoclaidomastoid muscle when choosing a puncture site. Needle insertion through the muscle should be avoided whenever possible. It can lead to bleeding and painful hematoma.

 

The indicator on the transducer should be oriented in the same direction as the indicator on the screen and located in the upper left hand side of the display. It can be used as a reference point when directing the needle towards the vessel of interest.

The transducer is placed in transverse orientation over the triangle formed by the two heads of the SCM.  Slowly slide the probe distally, until you find the area of interest, two dark and oval or round appearing vessels.  Use the transducer to compress the vein to confirm that it is indeed the vein and not the artery (Video clip 1).  Position the vein in the center of your image and place the needle to the midline of the transducer. Estimate or measure the depth of the IJ vein from the skin surface.  You can use the same distance when determining how far from the transducer the needle should enter the skin when the angle of insertion is close to 45 degrees (Figure 4 and 5).  In this scenario it is also important to remember that the length of the needle should be at least 1.4 times as long as the measured depth of the vein (Illustration 1).  Align the needle with the longitudinal axis of the vein while advancing it.

Video clip 1:  Shows compression of left internal jugular vessel.

	Figure 4		Figure 5

Figure 4:  Patient preparation and position for right IJ central line placement.
Figure 5:  Needle insertion technique right IJ.

Illustration 1: When the needle is inserted in a 45 degree angle, the path of the needle is approximately 1.4 times as long as the measured depth of the vessel. This can be estimated using the Phythagorean theorem, whereby the needle path equals the hypotenuse (c) and depth of the vessel and distance from transducer are the legs a and b of the triangle.

Advance the needle under direct ultrasound vision (‘dynamic technique’).
The sonographic appearance of the needle tip on the screen is a hyperechoic structure that casts a narrow shadow called “ring-down” artifact (Figure 6).  Following cannulation of the vein using ultrasound guidance, standard Seldinger technique should be used to place the catheter during which ultrasound is usually not needed.
The technique for central venous access of the Femoral Vein (FV) is similar to the above descibed IJ approach. Especially in patients were the femoral vein runs inferior to the artery, ultrasound can guide in a more oblique approach, minimizing the risk of accidential arterial puncture.

 

Figure 6:  Ring-down artifact over left IJ vein.

	Video clip 2a		Video clip 2b

Video clip 2a: Central line insertion left IJ. Video clip 2b: Central line insertion right IJ.

Peripheral Venous Access
Patient is placed in supine position with tourniquet applied to assist in vein engorgement.  Transducer is placed on the antecubital fossa in transverse axis and the same technique described above is used to identify and cannulate the peripheral vein of interest. An alternative approach is positioning the transducer in a long or sagittal axis to the vessel of interest.  This is very helpful to confirm that an approporiate angle was used to cannulate the vessel.

	Video clip 3		Video clip 4

Video clip 3:  Compression test of peripheral vein. Video clip 4: Catheter insertion peripheral vein.

 

Video clip 5: Color Doppler showing good position and patency of IV catheter. The IV flush is seen as a rainbow-colored "twinkle" on color Doppler. Note that the diameter of the vein is now significantly smaller without the tourniquet applied.

IV.  Pathology
Remember that central or peripheral veins can be thrombosed or contain a permanent catheter which makes them unsuitable for cannulation.

 

V.  Pearls and Pitfalls Failure to identify the needle in the tissue.  Remember to look for the ring-down artifact to avoid this. Failure to distinguish between vein and artery.  Remember to look for the compressible vessel.  Doppler flow can be used if necessary. Angling the transducer towards the entry site of the needle on the skin may help visualize the needle earlier. Avoid advancing the catheter if the needle tip is not visualized. Placing the patient in a supine and Trendelenburg position will help facilitate central venous access. Having the  patient perform a Valsalva maneuver will help engorge the internal jugular vein. Ideal positioning of neck should be midline or slightly lateral.  Excessive head rotation may cause dangerous overlay of the internal jugular vein over the carotid artery. Use caution when utilizing a long axis approach to central venous cannulation due to the inability to maintain visualization of the carotid artery at all times. Estimate the length of the needle path and choose a catheter with the appropriate length. Failure to use sterile ultrasound gel for line placement.  If not available you can substitute with a package of surgical lubricant.

 

VI.  Reference

1 Hudson PA, Rose JS.
Real-time ultrasound guided internal jugular vein catheterization in the emergency department. Am J Emerg Med.1997;15:79-82.

2 Slama M, Novara A, Safavian A, Ossart M, Safar M, Fagon JY.
Improvement of internal jugular vein cannulation using an ultrasound-guided technique. Intensive Care Med.1997;23:916-919.

3 Teichgräber UK, Benter T, Gebel M, Manns MP.
A sonographically guided technique for central venous access. AJR.1997;169:731-733.

4 Denys BG, Uretsky BF, Reddy PS.
Ultrasound-assisted cannulation of the internal jugular vein. A prospective comparison to the external landmark-guided technique. Circulation.1993;87:1557-1562.

5 Keyes LE, Frazee BW, Snoey ER, Simon BC, Christy D.
Ultrasound-guided brachial and basilic vein cannulation in emergency department patients with difficult intravenous access. Ann Emerg Med.1993;34:711-714.