Anatomy and Physiology
There are three main access sites for the placement of central venous catheters, namely internal jugular, common femoral, and subclavian veins. These are the preferred sites for temporary prominent venous catheter placement. Additionally, for mid-term and long-term central venous access, the basilic and brachial veins are utilized for peripherally inserted central catheters (PICCs). A discussion of tunneled catheters and other central access obtained via advanced interventional radiology techniques is beyond the scope of this article. We will focus on the three main sites of access routinely used for short-term (days to weeks) central access.
Understanding the relevant anatomy and adjacent structures is crucial when placing a CVC. The decision of where to place a central line is typically based on clinical parameters and individual clinician experience and preference. Each anatomical site has relative advantages and disadvantages, and one spot is unlikely to be the best choice for every patient. While the evidence does not suggest only one place, each location has known risks and benefits.
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The internal jugular vein (IJ) is often chosen for its reliable anatomy, accessibility, low complication rates, and ability to employ ultrasound guidance during the procedure.[9] The individual clinical scenario may dictate laterality in some cases (such as with trauma, head and neck cancer, or the presence of other invasive devices or catheters). Still, all things being equal, many clinicians prefer the right IJ. Compared to the left, the right IJ forms a more direct path to the superior vena cava (SVC) and right atrium. It is also wider and more superficial, thus presumably easier to cannulate.[14]
The IJ is located anterolateral to the common carotid artery, typically in the superior portion of the triangle created by the two heads of the sternocleidomastoid (SCM) muscle and the clavicle. The internal jugular vein joins the subclavian vein to form the brachiocephalic vein. The right and left brachiocephalic veins join to form the SVC. When anatomic landmarks are used, the IJ site can be accessed anteriorly, centrally, or posteriorly about the bifurcation of the SCM. Generally speaking, the central approach is most commonly used. Still, some have argued that the posterior approach is safest (being furthest from the lung apex and the carotid artery) and that the anterior approach is the easiest (as the carotid artery forms a readily palpable reference landmark). While there may still be no consensus about the correct landmark-based approach, most experts agree that ultrasound guidance provides the best chance of locating the vein and avoiding other structures owing to anatomic variability.[15][16]
The subclavian vein site has the advantage of low rates of both infectious and thrombotic complications.[17] Additionally, the SC site is accessible in trauma when a cervical collar negates the choice of the IJ. However, disadvantages include a higher relative risk of pneumothorax, less accessibility to use ultrasound for CVC placement, and the non-compressible location posterior to the clavicle. At the site of puncture for CVC placement, the subclavian vein lies just posterior to the clavicle. Still, the vessel takes a tortuous route as it extends medially from the axillary vein. As the vein courses along the clavicle, from lateral to medial, it progresses from the lateral border of the first rib, slopes cephalad at the middle third of the clavicle, then caudally merges with the internal jugular vein just posterior to the sternoclavicular joint. Of note, the subclavian vein is closely associated with several important structures. The vein is typically anterior and superior to the subclavian artery. The lung is just inferomedially to the subclavian vein, in close approximation to the lateral first rib. The phrenic nerve courses just deep to the brachiocephalic vein at the confluence of the subclavian vein and internal jugular vein. The brachial plexus and right-sided thoracic duct are also nearby and vulnerable to injury.[18] While ultrasound (US) guidance methods have been documented, access at this site is often performed without US guidance in a landmark-guided technique.[19] Data suggests that US guidance may reduce the rates of arterial puncture, pneumothorax, and brachial plexus injury; however, many clinicians are still more comfortable with landmark-guided placement for SC central venous catheters.[16][20][21][22]
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The SC vein can be accessed above or below the clavicle, though the infraclavicular method is far more commonly employed. The supraclavicular approach offers a well-defined landmark for insertion at the clavisternomastoid angle, a shorter distance from a puncture to the vein, and a straighter path to the SVC, with less proximity to the lung.[22] Authors have used these findings and the observation that ultrasound guidance is easier to perform with the supraclavicular approach to suggest that the infraclavicular approach should no longer be the SC CVC insertion method.[23] However, other studies have found that the supraclavicular approach leads to a higher incidence of hematoma formation, with comparable rates of other complications, offering support for maintaining the status quo.[24]
The femoral site is sometimes preferable in critically ill patients because the groin is free of other resuscitation equipment and devices which may be required for monitoring and airway access. Central venous access in the common femoral vein offers the advantage of being an easily compressible site, which may be helpful in trauma and other coagulopathic patients.[25] Additionally, unlike the IJ and SC sites, iatrogenic pneumothorax is not a concern. Patients may be more comfortable with a femoral CVC because it allows relatively free movement of the arms and legs compared to other sites. However, femoral CVCs are typically associated with increased thrombotic complications and likely an increased rate of catheter-associated infections. However, studies have shown conflicting results about the real risk of infection when the proper sterile technique is used.[5][26][27][28]
Unlike IJ or SC lines, femoral central lines do not allow for accurate measurement of central venous pressure (CVP), though this is not important in every clinical scenario. The common femoral vein is located within the femoral triangle. This region is outlined by the adductor longus medially, sartorius muscle laterally, and the inguinal ligament superiorly. There are important anatomical considerations to keep in mind when accessing this particular site. Whereas in the neck, the (carotid) artery is medial to the (internal jugular) vein, the artery is lateral to the vein in the leg. The mnemonic NAVEL is useful for recalling the order of lateral to medial structures: femoral nerve, femoral artery, common femoral vein, “space” (femoral canal), and lymphatics.[29] Knowing this anatomy or landmark-guided central line placement band is important because ultrasonography may appear similar.[11]
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