Anatomy:The Important Internal Anatomy and Surface Landmarks in Catheterization of the Internal Jugular Vein |
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When placing a central venous catheter in the internal jugular vein , it becomes vital to know the internal anatomy and the surface landmarks which will guide you to help ensure a safe and successful cannulation. The internal jugular vein begins just medial to the mastoid process at the base of the skull. (Remember from anatomy that the carotid artery, internal jugular vein, and the vagus nerve are all contained in the same “carotid sheath†in the neck ) The internal jugular vein runs directly inferior from the mastoid process, passing under the sternal end of the clavicle. Here it joins the subclavian vein, and then runs into the superior vena cava and then into the right atrium. As you know, the right atrium pumps blood through the tricuspid valve into the right ventricle, which sends the blood through the pulmonary valve into the pulmonary artery . The pulmonary artery then divides into left and right branches heading towards the capillary beds of the lungs.
Looking at the surface anatomy, the internal jugular vein courses like a straight line down from the mastoid process to the medial side of the insertion point of the clavicular head of the sternocleidomastiod muscle (SCM.) Recall that the SCM has two heads, the clavicular (lateral) head which inserts laterally on the clavicle, and the sternal (medial) head , which inserts medially on the sternum – giving the whole muscle the shape of an upside-down “V.†For purposes of internal jugular vein access, an important anatomic triangle is formed by the two heads of the SCM and the medial 1/3 of the clavicle. It is within this triangle that the right IJ is most safely and readily cannulated. Within this triangle, the carotid artery lies medial and slightly posterior to the internal jugular vein; therefore here there is less chance of accidentally puncturing the carotid artery during catheter insertion (which is a bad thing to do!)
Above is a dissection photo of the left anterior triangle the neck, clearly showing the internal jugular vein (InJ) with the carotid artery (CC) lying more medial. The clavicular head of the sternocleidomastiod muscle (SCM) is also visible, with the sternal head of the SCM (not shown) having been pulled back. Also visible: Sh=sternohyoid; SOm=superior belly of omohyoid; IOm=inferior belly of omohyoid; Sth=stylohyoid; AnD=anterior belly of digastric; PD=posterior belly of digastric; AC=ansa cervicalis; Hn=hypoglossal nerve; SG=submandibular gland.
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