In caring for patients who are critically ill, access to the central venous circulation is important. Central venous access allows the placement of various types of intravenous (IV) lines to facilitate the infusion of fluids, blood products, and drugs and to obtain blood for laboratory analysis. It is also an essential procedure in patients in whom placement of a line in a peripheral vein is impossible. A central line may be the only means of venous access in such cases.
Subclavian and internal jugular lines can allow the measurement of central venous pressure (CVP), an important parameter to gauge if a patient has been given an adequate amount of fluids.
Three central veins are typically used for venous access:
Internal jugular vein (IJV)
The capacity to place a line in the IJV is an important skill; this is the preferred vein for placement of a transvenous pacemaker because it is a straight line down the vein to the right side of the heart.  Given that it can be compressed, the IJV can be used for central venous access in patients who have impaired blood clotting. However, in such patients, the femoral vein is most often used.
There are three traditional approaches to the IJV:
The central and posterior approaches are most commonly used and are less likely to result in puncture of the carotid artery. This article describes the posterior approach to cannulation of the IJV.
Indications for the posterior approach to the IJV are the same as for any of the indications for a central line. They include the following:
Fluid resuscitation requiring a large-bore IV line for medical or trauma resuscitation
Need for a multilumen IV line
Lack of peripheral access
Measurement of CVP
Access via the superior vena cava to the right ventricle for passage of a venous pacemaker
Access to the pulmonary artery via the right ventricle for passage of a Swan-Ganz catheter
Access to a large vein for temporary renal dialysis
Access to a large vein for administration of hypertonic solutions (eg, for total parenteral nutrition)
No absolute contraindications exist to placement of a central line in the IJV via the posterior approach.
Relative contraindications revolve around mechanical problems of access to the neck. Skin infection, abscess, trauma, scarring, or mass along the side of the neck would make cannulation of the IJV difficult and hazardous. In addition, obesity may obscure landmarks and increase the risk of complications.
A coagulopathy, regardless of etiology, is a relative contraindication even though the IJV, unlike the subclavian vein, is compressible. The compressibility of the IJV allows it to be used for central line placement in a patient with a clotting disorder.
The ability to turn the head away from the side where the line is being placed, though not essential, is helpful with the posterior approach to the IJV. In patients with limited neck mobility (eg, trauma patients who do not have the cervical spine cleared), the posterior approach can be quite difficult. 
Finally, cooperation of the patient is essential because the lung and carotid artery are nearby and the risk of injury is excessive if the patient moves during the procedure.
A preassembled kit for central line cannulation is used, typically containing the following equipment:
Local anesthetic (eg, lidocaine 1%) with needles and syringes
Thin-walled 14- to 18-gauge introducer needle
J-tip guide wire and semirigid dilator
Central line catheter
Antiseptic solution and applicator (eg, povidone-iodine or chlorhexidine)
Sterile drapes, gloves, and gown
Nonsterile mask and cap
No. 11 blade scalpel
Suture (commonly, 3-0 silk on a straight cutting needle)
Antibiotic ointment for the dressing
Plastic occlusive dressing
The most common means of anesthesia for placement of an IV line in the IJV is use of a local anesthetic (eg, lidocaine). Generous administration of a local anesthetic in the area just posterior to the midportion of the sternocleidomastoid is typically sufficient for the patient's comfort before tunneling of the catheter.
Care must be taken not to inject the anesthetic into either the internal jugular vein or the carotid artery. Additional local anesthetic is used on the skin for the sutures that secure the catheter to the skin. (See Local Anesthetic Agents, Infiltrative Administration.)
In certain patients, the pain of the procedure is such that additional sedation, pain control, or both might be prudent. Titrated doses of midazolam, fentanyl, or both are useful because these are agents with relatively short durations of action and minimal cardiovascular effects. (See Procedural Sedation.)
A key aspect of central line placement in the IJV is proper positioning of the patient. Putting the patient in the Trendelenburg position dilates the vein and makes cannulation easier. In addition, this position makes the external jugular vein (EJV) more prominent. The point at which the vein crosses the sternocleidomastoid is a key landmark in the posterior approach.
Some patients cannot tolerate having their head lower than their feet. In such patients, laying them down as flat as possible is important to the success of the procedure.
The patient’s head should be turned away from the side of the internal jugular vein being accessed to provide access to the side of the neck. Having an assistant hold the patient’s head in that position is often necessary. Turning the patient’s head to the side also makes the sternocleidomastoid more prominent and makes the landmarks easier to identify.
The method most commonly employed to place a cannula in the internal jugular vein (IJV) is the Seldinger wire technique. Various catheters can be placed in the IJV, including single lumen, multiple lumen, large-bore sheaths, and dialysis catheters such as the Quinton catheter.
The posterior approach does not lend itself as easily to ultrasonographic guidance as the anterior approach does. However, the use of ultrasonography can allow visualization of the IJV and carotid artery and is often helpful regardless of the particular approach taken to the IJV. [3, 4, 5, 6]
In placing a central line in the IJV or the subclavian vein, the Trendelenburg position distends the veins in the patient's neck and thereby makes them easier to cannulate. Either side of the neck can be used, but the right IJV is most often used.
Cannulation of internal jugular vein via posterior approach
To begin the procedure, inspect the neck to identify landmarks, including the posterior edge of the sternocleidomastoid (see the image below) and the external jugular vein (EJV), and palpate the carotid artery to ascertain its position. Also, look for any skin infections or neck masses.
Place the patient in the Trendelenburg position, 10-15o, and turn the patient’s face to the contralateral side.
Drape with sterile sheets or towels as with any sterile procedure. The use of large sterile sheets to cover the patient and the use of a cover over the hair, a mask, and a sterile gown and gloves for the practitioner have been shown to decrease the rate of line infection. [7, 8]
Clean the skin of the patient’s neck down to the clavicle and upper chest with the antiseptic solution, and apply the drape to allow visualization of the middle of the neck.
Identify the point of insertion for the introducer needle along the posterior edge of the sternocleidomastoid at the level just superior to where the EJV crosses the muscle. This is typically one third of the distance between the mastoid and the clavicle.
Anesthetize the skin and subcutaneous tissue at this point, aspirating so that lidocaine is not injected directly into a vessel. Typically, a 25-gauge needle is used to administer the local anesthetic. This same needle can be used to localize the IJV to determine how deep and at what angle to the skin the vein might be. Even a long 25-gauge needle may not have sufficient length to reach the IJV. However, hunting for the vein with a smaller-gauge needle tends to be less traumatic than using the introducer needle would be.
Place the introducer needle at the area of anesthetized skin, aiming down toward the sternal notch. Advance the needle while aspirating; the easy flow of venous blood assures that the needle is in the internal jugular vein. Typically, the vein is entered within 1-3 cm; if the vein is missed, draw the needle all the way back to the skin before redirecting it.
If the bevel of the introducer needle is swung back and forth in the deeper tissues, a vessel or nerve may be inadvertently lacerated. Redirecting the needle more laterally, toward the sternoclavicular joint as opposed to the notch, often allows the vein to be entered. [9, 10]
Once venous blood is free-flowing in the syringe, carefully remove the syringe so that the needle remains in the IJV.
Introduce the guide wire down the needle, with the J-wire bend going in first. The wire should advance with little resistance. If any significant resistance is noted, remove the guide wire and ascertain if the needle is in the vein by checking for free-flowing blood with syringe aspiration.
Once the guide wire is in place, carefully remove the needle, leaving the guide wire in the vein. Hold on to the wire at all times so that it is not lost down the vein.
Make a skin incision is made around the entry point. This incision should be relatively generous because if it is too small, the skin will tent around the catheter and will eventually necrose, which can quickly lead to a catheter site infection.
Carefully advance the semirigid dilator along the guide wire, and create a passage for the catheter in the soft tissue. Rotating the dilator back and forth allows more gentle insertion and lowers the risk of tearing the vein.
Thread the catheter over the guide wire to the level of the skin. Back the wire out so that it just sticks out of the intravenous (IV) hub at the end of the catheter. Then hold the guide wire firmly while advancing the catheter over the wire into the IJV. Once the catheter is advanced to an appropriate depth, remove the guide wire.
Reattach a syringe to the catheter, and verify that blood can be easily aspirated; this confirms that the catheter is indeed in the vein. Flush all lumina of the line with saline.
Place sutures to hold the catheter in place. Most often, a wing device is placed over the catheter to allow it to be secured to the skin. Place antiseptic ointment over the entry point, and cover the site with an occlusive dressing. 
Finally, obtain a chest radiograph to confirm correct placement and to verify that no injury to the lung (ie, pneumothorax) has occurred.  Hold off on infusion of fluids until radiographic confirmation of appropriate placement is completed. The tip of the line should be above the right atrium and below the level of the clavicle. If the tip is in the heart, it can whip back and forth as the heart contracts, and penetration of the heart wall can occur.
Adequate local anesthesia in the area of cannulation is important to the success of this procedure. This is important for the patient's comfort and helps the patient hold still during the procedure.
A long 25-gauge needle can be used for the administration of the local anesthetic and to ascertain the position of the IJV. This can give the practitioner an idea of the depth and direction of the IJV without the trauma associated with searching for the vein with the larger introducer needle.
Take care to avoid injecting the local anesthetic into a vessel when hunting for the vein.
Placing the patient in the Trendelenburg position helps dilate the IJV. The bigger the vein, the easier it is to cannulate. Once the guide wire is in place, the patient can be taken out of the Trendelenburg position, which is often uncomfortable.
Thorough cleansing of skin and complete draping of the patient and practitioner have been shown to decrease infections of a central line. These lines often must remain in place for a long time; therefore, it is important to perform the procedure in as sterile a manner as possible.
As in any procedure performed to gain access to a central vein, the angle of the introducer needle may have be altered if the vein is not cannulated the first time. The large-bore introducer needle must be withdrawn out to the skin before the angle of insertion is adjusted.
Moving a beveled needle back and forth in an area with several large vessels can lacerate those vessels.
The introducer needle should be advanced slowly to make sure that it does not go entirely through the vein. Ultrasonographic guidance can aid in the establishment of central venous access.  (See Ultrasonography Assisted Central Line Placement.) However, a 2009 study reported that 64% of the residents participating penetrated the posterior wall of the IJV, even under ultrasonographic guidance. 
One of the more common, and feared, complications of central line placement in the IJV is injury to the lung resulting in pneumothorax or tension pneumothorax. This is particularly true if the cupula of the lung is above the clavicle, as it can be inadvertently punctured, causing a pneumothorax.
Any shortness of breath following or during the procedure warrants immediate investigation with chest radiography. Air embolism can occur if the catheter is allowed to be open to the air; to prevent air aspiration, the practitioner should keep his or her finger over the hub when the guide wire is removed or a syringe is attached or removed.
A hematoma at the site of insertion can occur, particularly if the carotid artery is punctured.
Loss or breakage of the guide wire has been described, and control of the wire must be maintained at all times. If any resistance is encountered during withdrawal of the wire through the needle, remove the needle and the wire as a single unit to avoid breakage of the wire against the bevel of the needle.
Laceration of a vessel or nerve has been described with IJV central line placement.