Central venous line

From greek.doctor

A central venous line or central venous catheter, often shortened to simply a central line, is a catheter inserted into a central vein (as opposed to a peripheral vein for a regular peripheral venous catheter). The jugular, subclavian, or femoral vein can be used, with the jugular vein being the most common.

A central line is, like an arterial line, often used for critically ill patients. Blood samples can be taken from them and fluids and medications can be delivered through them. A central line is usually stable over a longer period of time than a peripheral venous catheter and is therefore also often used for people who need long-term intravenous administration, like antibiotics for endocarditis. It also allows for the measurement of certain parameters:

  • SvO2 = mixed venous oxygen saturation
    • The oxygen saturation of the blood in the RV/pulmonary artery, where blood from the IVC and SVC have been mixed
    • Normally ~75%
  • ScvO2 = central venous oxygen saturation
    • The oxygen saturation of the blood in the SVC
    • Normally 2 – 3% lower than SvO2
  • CVP = central venous pressure
    • The pressure of venous blood in the vena cava. Corresponds to the right atrial pressure and the preload
    • Normally 5 – 10 cmH2O

A central line is placed with Seldinger technique and ultrasonography guidance.

Indications

  • Measurement of central venous pressure and oxygenation levels in critically ill patients
  • Administration of medications longer term (> approx 5 days)
  • Administration of large amounts of infusions (for example in shock, blood loss)
  • Administration of certain medications which are too toxic for peripheral venous administration (certain chemotherapeutics)
  • Total peripheral nutrition

Midline catheter and PICC line

A midline catheter is sort of middle-line between a peripheral and central venous line. It's a catheter inserted into a vein of the upper arm, usually the proximal basilic or cephalic vein. The catheter is long so that the tip of the catheter (and thus the point at which fluids and medications are delivered) is located in the axillary vein.

A peripherally inserted central catheter (PICC), sometimes called a PICC line, is similar to a midline in that it's inserted into a vein in the upper arm, but the catheter is longer so that the tip lies in the superior vena cava.

The indications for midline and PICC line catheters are similar, but midline catheters are easier to place and have lower risks of infection. However, PICC lines can remain for longer, up to 1 year.

Tunneled central venous catheters

A tunneled central venous catheter (of which Hickman catheter is the most well known type) is a type of catheter which is inserted into the skin 10 - 20 centimetres away from the entry point of the central vein, usually somewhere on the lower thorax. The catheter is placed in a "tunnel" under the skin from the entry point to the right subclavian vein, where it is inserted, and the tip is placed in the superior vena cava.

Due to the longer distance from the entry point through the skin to the perforation of the central vein, the risk of infection is lower. The indications are the same as for regular non-tunneled central venous catheters.

Venous access port

A venous access port (VAP) is a form of central venous catheter where the distal end is placed in a central vein and the proximal end is connected to a small chamber that is placed surgically under the skin on the chest. The VAP can be palpated. To access the central vein, a specialised needle (VAP needle) is used to penetrate the overlying skin and into the small chamber. The chamber can be used 2000 times before it must be exchanged. This device is used in patients who require repeated infusions or blood tests over time.

Complications

During placement of CVCs, pneumothorax can occur. Accidental puncture of an artery is also possible. Other than that, the most common complication is infection, more specifically called central line-associated bloodstream infection (CLABSI). Sterile insertion and maintainance is essential to reduce the risk. CVCs should be removed when no longer needed.