Local Anatomy and Subclavain Vein
The axillary vein courses medially to become the subclavian vein as it passes anteriorly to the first rib. After crossing the first rib, the vein lies posterior to the medial third of the clavicle at the change in curvature of the clavicle. Deep to the vein is the anterior scalene muscle followed by the subclavian artery.
The dome of the right lung lies lower than the left lung which may extend above the first rib. The thoracic duct (on the left) and the lymphatic duct on the right pass over the anterior scalene muscle and enter the subclavian vein near its junction with the IJ vein.
The patient should be positioned in Tredelenburg with slightly extended shoulders. The most common technique involves the infraclavicular (IC) approach. Venipuncture should occur 1 cm lateral to the curvature of the middle third of the clavicle with the needle pointing horizontally directed at the sternal notch. In order to decrease malposition of the guidewire in the ipsilateral IJ vein, ensure that the bevel of the needle is directed towards the SVC and a sterile finger can be placed in the ipsilateral supraclavicular fossa. The needle can be used to feel the clavicle and should be advanced just under the clavicle directed towards the sternal notch.
Local anatomy and IJ vein
There are numerous described approaches to the IJ. The landmark approach most widely used is between the medial and lateral heads of the sternocleidomastoid muscle and lateral to the carotid artery in most cases.
The IJ vein is a readily compressible vessel. Positioning the patient in Trendelenburg will increase the size of the IJ vein. While mild rotation of the neck away from the side of IJ insertion will aid in venipuncture, over-rotation and overextension can actually cause the SCM to compress the IJ vein (Lieberman JA).
Variant anatomy of the right IJ vein.
The right IJ vein should be attempted at cannulation first given the incidence of fewer complications given that the dome of the left lung is higher than the right, the thoracic duct empties on the left, and there is a straight course to the SVC on the right (Sulek CA).
Some studies have found that the carotid artery may overlap the internal jugular 54% of the time while 5.5% of the time the IJ vein maybe medial to the carotid artery (Gordon AC, Troianos CA, Denys BG). This stresses the importance of ultrasound localization of the internal jugular vein relative to the carotid artery.
Local anatomy and femoral vein
The femoral vein is located medial to the femoral artery and the femoral nerve below the inguinal ligament. It is important the venipuncture occurs at 1-2 cm below the level of the inguinal ligament and that an assistant pushes aside any significant pannus. US guidance is useful when the femoral arterial pulse cannot be located.
Once the vein has been punctured, the modified Seldinger technique is used to insert the catheter.