A central venous catheter (CVC), also known as a central line (c-line), central venous line, or central venous access catheter, is a catheter placed into a large vein. It is a form of venous access. Placement of larger catheters in more centrally located veins is often needed in critically ill patients, or in those requiring prolonged intravenous therapies, for more reliable vascular access. These catheters are commonly placed in veins in the neck (internal jugular vein), chest (subclavian vein or axillary vein), groin (femoral vein), or through veins in the arms (also known as a PICC line, or peripherally inserted central catheters).

Central lines are used to administer medication or fluids that are unable to be taken by mouth or would harm a smaller peripheral vein, obtain blood tests (specifically the "central venous oxygen saturation"), administer fluid or blood products for large volume resuscitation, and measure central venous pressure. The catheters used are commonly 15–30 cm in length, made of silicone or polyurethane, and have single or multiple lumens for infusion.

  1. Difficult peripheral venous access – central venous catheters may be placed when it is difficult to gain or maintain venous access peripherally (e.g. obesity, scarred veins from prior cannulations, agitated patient).
  2. Delivery of certain medications or fluids – medications such as vasopressors (e.g., norepinephrine, vasopressin, phenylephrine etc.), chemotherapeutic agents, or hypertonic solutions are damaging to peripheral veins and often require placement of a central line. Additionally, catheters with multiple lumens can facilitate the delivery of several parenteral medications simultaneously.
  3. Prolonged intravenous therapies – parenteral medications that must be delivered for extended periods of time (more than a few days) such as long-term parenteral nutrition, or intravenous antibiotics are administered through a central line.
  4. Specialized treatment – interventions such as hemodialysis, plasmapheresis, transvenous cardiac pacing, and invasive hemodynamic monitoring (e.g. pulmonary artery catheterization) require central venous access.

There are no absolute contraindications to the use of central venous catheters. However, there are risks and complications associated with the placement of central lines, which are addressed below.

Complications

Central line insertion may cause several complications. The benefit expected from their use should outweigh the risk of those complications.

Pneumothorax

The incidence of pneumothorax is highest with subclavian vein catheterization due to its anatomic proximity to the apex of the lung. In the case of catheterization of the internal jugular vein, the risk of pneumothorax is minimized by the use of ultrasound guidance. For experienced clinicians, the incidence of pneumothorax is about 1.5–3.1%. The National Institute for Health and Care Excellence (UK) and other medical organizations recommend the routine use of ultrasonography to minimize complications.

If a pneumothorax is suspected, an upright chest x-ray should be obtained. An upright chest x-ray is preferred because free air will migrate to the apex of the lung, where it is easily visualized. Of course, this is not always possible, particularly in critically ill patients in the intensive care unit. Radiographs obtained in the supine position fail to detect 25–50% of pneumothoraces. Instead, bedside ultrasound is a superior method of detection in those too ill to obtain upright imaging. If the carotid is accidentally cannulated and a catheter is inserted into the artery, the catheter should be left in place and a vascular surgeon should be notified because removing it can be fatal. The problem of central line-associated bloodstream infections (CLABSI) has gained increasing attention in recent years. They cause a great deal of morbidity (harm) and deaths, and increase health care costs. Those who have a CLABSI have a 2.75 times increased risk of dying compared to those who do not.

If a central line infection is suspected in a person, blood cultures are taken from both the catheter and a vein elsewhere in the body. If the culture from the central line grows bacteria much earlier (>2 hours) than the other vein site, the line is likely infected. Quantitative blood culture is even more accurate, but this method is not widely available.

Antibiotics are nearly always given as soon as a patient is suspected to have a catheter-related bloodstream infection. However, this must occur after blood cultures are drawn, otherwise the culprit organism may not be identified. The most common organisms causing these infections are coagulase negative staphylococci such as staphylococcus epidermidis. Evidence suggests that there may not be any benefit associated with giving antibiotics before a long-term central venous catherter is inserted in cancer patients and this practice may not prevent gram positive catheter-related infections. However, for people who require long-term central venous catheters who are at a higher risk of infection, for example, people with cancer who at are risk of neutropenia due to their chemotherapy treatment or due to the disease, flushing the catheter with a solution containing an antibiotic and heparin may reduce catheter-related infections. The guideline makes several other recommendations to prevent line infections. Routine replacement of lines makes no difference in preventing infection. The CDC makes many recommendations regarding risk reduction for infection of CVCs, including:

  • The preferred site of insertion (including for non-tunneled catheter placement), from an infection prevention point of view, is in the subclavian vein, and to generally avoid the femoral vein if possible.
  • There is no clear recommendation for a tunneled catheter site in the guidelines.
  • Selection of catheters should include those with minimal ports to accomplish the clinical goal.
  • Sterile gloves are required for CVC
  • Full body sterile drapes, cap, mask, gloves are required for placement of CVCs
  • The catheter site should be monitored visually and with palpation (through dressing) on a regular basis to assess for infection.
  • It is, however, acceptable to use clean, non-sterile, gloves for changing the dressing of intravascular catheters.
  • Both chlorhexidine and povidone-iodine are acceptable skin cleansers, though chlorhexidine is preferred.
  • For short-term CVC sites, dressings must be changed at least every 7 days for transparent dressings, and every 2 days for gauze dressings.
  • For long-term implanted or tunneled catheters, dressings are to be changed no more than once weekly unless soiled or loose.
  • Routine removal and replacement of a central venous catheter is not recommended. While central line catheters should be removed as soon as they are no longer necessary, scheduled removal and replacement, whether over a guidewire or with a new puncture site, has not been shown to be beneficial in preventing infections.
  • Medication impregnated dressing products can reduce the risk getting catheter-related blood stream infection.
  • There is inconclusive evidence whether longer interval of changing dressings for central venous access devices is associated with more or less infections.
  • It is unclear whether cleaning the skin with antiseptics or without skin cleansing can reduce the rate of catheter-related bloodstream infections. The lack of clarity is due to the low quality of some of the studies used in the meta-analysis.

Using checklists, which detail the step by step process (including sterile techniques) of catheter placement has been shown to reduce catheter related bloodstream infections. This is often done with an observer reviewing the checklist as the operator places the central catheter. It is indirectly seen in these images before and after radiocontrast infusion, as the radiocontrast collects around the catheter.]]

Venous catheters may occasionally become occluded by kinks in the catheter, backwash of blood into the catheter leading to thrombosis, or infusion of insoluble materials that form precipitates. However, thrombosis is the most common cause of central line occlusion, occurring in up to 25% of catheters. It is thought this risk stems from activation of clotting substances in the blood by trauma to the vein during placement. The risk of blood clots is higher in a person with cancer, as cancer is also a risk factor for blood clots. As many as two thirds of cancer patients with central lines show evidence of catheter-associated thrombosis. Additionally, studies suggest that short term use of CVCs in the subclavian vein is less likely to be associated with blood clots than CVCs placed in the femoral vein in non-cancer patients. The tip of the catheter can also be misdirected into the contralateral (opposite side) subclavian vein in the neck, rather than into the superior vena cava.

Venous air embolism

Entry of air into venous circulation has the potential to cause a venous air embolism. This is a rare complication of CVC placement – however, it can be lethal. The volume and the rate of air entry determine the effect an air embolus will have on a patient. This process can become fatal when at least 200–300 milliliters of air is introduced within a few seconds. The consequences of this include: acute embolic stroke (from air that passes through a patent foramen ovale), pulmonary edema, and acute right heart failure (from trapped air in the right ventricle) which can lead to cardiogenic shock. There is inadequate evidence whether heparin saline flush is better than normal saline flush to maintain central venous catheter patency and prevent occlusion.

Insertion

thumb|Video of an ultrasound-assisted central line insertion through the internal jugular vein

Before insertion, the patient is first assessed by reviewing relevant labs and indication for CVC placement, in order to minimize risks and complications of the procedure. Next, the area of skin over the planned insertion site is cleaned. A local anesthetic is applied if necessary. The location of the vein is identified by landmarks or with the use of a small ultrasound device. A hollow needle is advanced through the skin until blood is aspirated. The color of the blood and the rate of its flow help distinguish it from arterial blood (suggesting that an artery has been accidentally punctured). Within North America and Europe, ultrasound use now represents the gold standard for central venous access and skills, with diminishing use of landmark techniques. Recent evidence shows that ultrasound-guidance for subclavian vein catheterization leads to a reduction in adverse events.

The line is then inserted using the Seldinger technique: a blunt guidewire is passed through the needle, then the needle is removed. A dilating device may be passed over the guidewire to expand the tract. Finally, the central line itself is then passed over the guidewire, which is then removed. All the lumens of the line are aspirated (to ensure that they are all positioned inside the vein) and flushed with either saline or heparin. Electromagnetic tracking can be used to verify tip placement and provide guidance during insertion, obviating the need for the X-ray afterwards.

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File:A technique for the fixation of central venous catheters.png|A central venous catheter secured to the skin with suture

Image:Subclavian central veinous catheter xray.png|Chest x-ray with catheter in the right subclavian vein

File:Mediastinal structures on chest X-ray, annotated.jpg|The outline of superior vena cava on a chest X-ray is labeled at left.

</gallery>

Catheter flow

Hagen–Poiseuille equation

The Hagen–Poiseuille equation describes the properties of flow through a rigid tube. The equation is shown below:

<math>Q = \Delta P * (\pi r^4/8\mu L)</math>

The equation shows that flow rate (Q) through a rigid tube is a function of the inner radius (r), the length of the tube (L), and the viscosity of the fluid (μ). The flow is directly related the fourth power of the inner radius of the tube, and inversely related to the length of the tube and viscosity of the fluid. This equation can be used to understand the following vital observations regarding venous catheters: that the inner radius of a catheter has a much greater impact on flow rate than catheter length or fluid viscosity, and that for rapid infusion, a shorter, large bore catheter is optimal because it will provide the greatest flow rate.

By site

Percutaneous central venous catheter (CVC)

A percutaneous central venous catheter, or CVC, is inserted directly through the skin. The internal or external jugular, subclavian, or femoral vein is used. It is most commonly used in critically ill patients. The CVC can be used for days to weeks, and the patient must remain in the hospital. It is usually held in place with sutures or a manufactured securement device. Commonly used catheters include Quinton catheters.

Peripherally inserted central catheters (PICC)

thumb|PICC line inserted in the upper arm (through the basilic vein)

A peripherally inserted central catheter, or PICC line (pronounced "pick"), is a central venous catheter inserted into a vein in the arm (via the basilic or cephalic veins) rather than a vein in the neck or chest. The basilic vein is usually a better target for cannulation than the cephalic vein because it is larger and runs a straighter course through the arm. The tip of the catheter is positioned in the superior vena cava.

However, PICC lines are desirable for several reasons. They can provide venous access for up to one year. The patient may go home with a PICC. They avoid the complications of central line placement (e.g. pneumothorax, accidental arterial cannulation), and they are relatively easy to place under ultrasound guidance and cause less discomfort than central lines.

Hemodialysis catheter

Hemodialysis catheters are large diameter catheters (up to 16 French or 5.3mm) capable of flow rates of 200–300 ml/min, which is necessary to maintain the high flow rates of hemodialysis. There are two channels: one is used to carry the patient's blood to the dialysis machine, while the other is used to return blood back to the patient. These catheters are typically placed in the internal jugular vein. Certain lines are impregnated with antibiotics, silver-containing substances (specifically silver sulfadiazine) and/or chlorhexidine to reduce infection risk.

Specific types of long-term central lines are the Hickman catheters, which require clamps to make sure that the valve is closed, and Groshong catheters, which have a valve that opens as fluid is withdrawn or infused and remains closed when not in use. Hickman lines also have a "cuff" under the skin, to prevent bacterial migration. The cuff also causes tissue ingrowth into the device for long term securement.

See also

  • Peter Pronovost (Work with CVCs)
  • Quinton catheter

References

  • Central Venous Catheter Placement & Pulmonary Artery Catheter – Vìdeo Dailymotion (without ultrasound guidance)
  • Video tutorial on how to start central venous lines in various locations
  • Central line care, comparison, indications, complications and uses