The AJV usually begins in the suprahyoid region through the confluence of several superficial veins. It has variable communications with the retromandibular or the facial vein and the IJV and descends between the median line and the anterior border of the sternocleidomastoid muscle. Near the thoracic level of the neck, the AJV passes beneath that muscle to open into the subclavian vein (in 54% of patients) or into the termination of the EJV (in 46%) (9,10). The AJV varies considerably in size, usually in an inverse proportion to the EJV (10). Most frequently, there are two AJV (right and left), but sometimes there is a single, often median localized AJV. Just above the sternum the two AJV communicate by a transverse trunk, the jugular venous arch (JVA), which traverses the midline of the neck between the superficial and the pretracheal layer of the cervical fascia. The JVA is sometimes also referred to as the anterior jugular arch (11). It is one of the vessels encountered in a low tracheostomy (12).
The IJV have rich anastomotic channels over the thyroid gland through the superior and middle thyroid veins (13). The inferior thyroid veins often confluence and terminate unpaired in the left innominate vein (LIV) providing an anastomotic channel between the thyroid venous plexus between both innominate veins. Small branches of the inferior thyroid veins sometimes drain into the JVA (10).
In unilateral occlusion of an innominate vein, one of these anastomotic channels over the anterior neck area is used as a collateral pathway to the opposite side (13). Enlargement and tortuosity of collateral vessels (e.g., JVA) are signs of associated venous obstruction (14).
CVC malpositioning into the AJVS usually occurs when the catheter enters the horizontal component of the AJVS, the JVA, by the EJV, which is the most common origin of the horizontal aspect of the AJVS (Fig. 6) (11).
The great variability of the AJVS and its clinical implications are illustrated by our three cases. In Case 1 (PAC via LIV and CVC via left IJV in JVA), it is striking that both catheters were placed in the JVA, and no unusual resistance was met during insertion. As described above, the JVA is a connecting vein between the AJV that frequently drains into the subclavian or EJV. Under typical anatomical conditions, it is impossible to correctly place a CVC by the pathway of the JVA. Therefore, we assume that in this patient, the anatomical variation is a JVA terminating in the RIV, allowing proper positioning of CVC and PAC. The most likely explanation is an obstruction of the LIV combined with a caudal course of the JVA, which probably arises from the confluence of the left sub-clavian and left IJV. Unfortunately, we do not have the radiological evidence to verify this. Ultrasound-guided cannulation procedures will allow the clinician to distinguish the AJV from the IJV. The addition of Doppler wave form analysis to the ultrasound examination virtually excludes the possibility of a more central venous occlusion or stenosis more than 80% if the wave pattern is normal (15). But even the combination of these two techniques does not identify the confluence of the vessels or predict the termination of the AJV. As a consequence, CVC tip positioning will be unpredictable.
In Case 2, the LIV was obstructed after 3 wk of CVC placement via the left IJV. Apparently, the AJVS had developed as a major collateral pathway (Fig. 3). In Case 3, the PAC had been placed correctly via the pathway of the LIV. However, the CVC was malpositioned in the AJV (see the horizontal and vertical aspects of the AJVS in Fig. 4). Placement of a catheter tip in vessels of small diameter increases the risk of catheter wedging, endothelial injury, thrombus formation, and vascular stenosis or perforation with extravasation of the infusate. Such positioning should be avoided, particularly when the catheter is used for infusion of hypertonic or hyperosmolar solutions that require vessels with larger blood flow for rapid dilution (16,17).
There are two take-home messages from these case reports on CVC placed in the AJVS. The AJVS, with its interconnections to the subclavian and deep jugular veins, provides an important collateral venous network across the neck, especially in unilateral occlusion of an innominate vein. Thus, correct placement of CVC via the AJVS may be possible. Conversely, CVC malpositioned in the AJV increase the risk for complications and should be removed.
The authors thank Jens Geiling for providing the illustration of the AJVS.
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