Central venous catheter

In medicine, a central venous catheter (CVC or "central venous line" or "central venous access catheter") is a catheter placed into a large vein in the neck (internal jugular vein), chest (subclavian vein) or groin (femoral vein). It is used to administer medication or fluids, obtain blood tests (specifically the "mixed venous oxygen saturation"), and directly obtain cardiovascular measurements such as the central venous pressure. Certain medications, such as inotropes and amiodarone, are preferably given through a central line.fact|date=June 2008

Types

Dependent on its use, the catheter is "monoluminal", "biluminal" or "triluminal", dependent on the actual number of tubes or lumens (1, 2 and 3 respectively,). Some catheters have 4 or 5 lumens, depending on the reason for their use.fact|date=June 2008

The catheter is usually held in place by a suture or staple and an occlusive dressing. Regular flushing with saline or a heparin-containing solution keeps the line and prevents thrombosis (formation of a blood clot). Certain lines are impregnated with antibiotics, silver-containing substances (specifically silver sulfadiazine) and/or chlorhexidine to reduce infection risk.fact|date=June 2008

Specific types of long-term central lines are the Hickman catheters, which require clamps to make sure the valve is closed, and Groshong catheters, which have a valve that opens as fluid is withdrawn or infused and remains closed when not in use.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 and Groshong lines need more specific measures to prevent infection. Hence, they are inserted into the jugular vein but then tunneled under the skin to maximize the distance a pathogen would need to travel to enter the bloodsteam. Hickman lines also have a "cuff" under the skin, again to prevent bacterial migration.fact|date=June 2008

Indications and uses

Indications for the use of central lines include:fact|date=June 2008
* Monitoring of the central venous pressure (CVP) in acutely ill patients to quantify fluid balance
* Parenteral nutrition
* Drugs that are prone to cause phlebitis in peripheral veins (caustic), such as:
**Calcium chloride
**Chemotherapy
**Hypertonic saline
**Potassium chloride
**Amiodarone
* Need for intravenous therapy when peripheral venous access is impossible
**Blood
**Medication
**Rehydration

Central venous catheters usually remain in place for a longer period of time, especially when the reason for their use is longstanding (such as total parenteral nutrition in a chronically ill patient). For such indications, a Hickman line, a PICC line or a portacath may be considered because of their smaller infection risk. Sterile technique is highly important here, as a line may serve as a "porte d'entrée" (place of entry) for pathogenic organisms, and the line itself may become infected with organisms such as "Staphylococcus aureus" and coagulase-negative Staphylococci.fact|date=June 2008

Insertion

The skin is cleaned, and local anesthetic applied if required. The location of the vein is then 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).fact|date=June 2008

The Seldinger technique is then employed to insert the line. This means that a blunt guidewire is passed through the needle, and the needle is then removed. A dilating device may be passed over the guidewire to slightly enlarge the tract, and 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.fact|date=June 2008

For jugular and subclavian lines, a chest X-ray is typically performed to ensure the line is positioned inside the superior vena cava.fact|date=June 2008

Complications

Central line insertion may cause a number of complications. The benefit expected from their use therefore needs to outweigh the risk of those complications.fact|date=June 2008

Pneumothorax

Pneumothorax (for central lines placed in the chest); the incidence is thought to be higher with subclavian vein catheterization. In catheterization of the internal jugular vein, the risk of pneumothorax can be minimized by the use of ultrasound guidance. For experienced clinicians, the incidence of pneumothorax is about 1%. Some official bodies, e.g. the National Institute for Health and Clinical Excellence (UK), recommend the routine use of ultrasonography to minimize complications. [cite web | author=National Institute for Health and Clinical Excellence | title= Technology appraisal: the clinical effectiveness and cost effectiveness of ultrasonic locating devices for the placement of central venous lines | url=http://www.nice.nhs.uk/guidance/index.jsp?action=byID&o=11474 | date=Sept 2002 | accessdate=2008-06-01]

Infection

All catheters can introduce bacteria into the bloodstream, but CVCs are known for occasionally causing "Staphylococcus aureus" and "Staphylococcus epidermidis" sepsis. Infection risks were initially thought to be less in jugular lines, but this only seems to be the case if the patient is obese.cite journal |author=Parienti JJ, Thirion M, Mégarbane B, "et al" |title=Femoral vs jugular venous catheterization and risk of nosocomial events in adults requiring acute renal replacement therapy: a randomized controlled trial |journal=JAMA |volume=299 |issue=20 |pages=2413–22 |year=2008 |month=May |pmid=18505951 |doi=10.1001/jama.299.20.2413]

If a patient with a central line develops signs of infection, blood cultures are taken from both the catheter and from a vein elsewhere in the body. If the culture from the central line grows bacteria much earlier (>2 hours) than the other site, the line is the likely source of the infection. Quantitative blood culture is even more accurate, but this is not widely available.cite journal |author=Safdar N, Fine JP, Maki DG |title=Meta-analysis: methods for diagnosing intravascular device-related bloodstream infection |journal=Ann. Intern. Med. |volume=142 |issue=6 |pages=451–66 |year=2005 |pmid=15767623 |doi=|url=http://www.annals.org/cgi/content/full/142/6/451]

Generally, antibiotics are used, and occasionally the catheter will have to be removed. In the case of bacteremia from "Staphylococcus aureus", removing the catheter without administering antibiotics is not adequate as 38% of such patients may still develop endocarditis.cite journal |author=Watanakunakorn C, Baird IM |title=Staphylococcus aureus bacteremia and endocarditis associated with a removable infected intravenous device |journal=Am. J. Med. |volume=63 |issue=2 |pages=253–6 |year=1977 |month=August |pmid=888847 |doi=10.1016/0002-9343(77)90239-X]

In a clinical practice guideline, the American Centers for Disease Control and Prevention recommends against routine culturing of central venous lines upon their removal.cite journal |author=O'Grady NP, Alexander M, Dellinger EP, "et al" |title=Guidelines for the prevention of intravascular catheter-related infections. Centers for Disease Control and Prevention |journal=MMWR. Recommendations and reports : Morbidity and mortality weekly report. Recommendations and reports / Centers for Disease Control |volume=51 |issue=RR-10 |pages=1–29 |year=2002 |pmid=12233868 |doi=|url=http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5110a1.htm] The guideline makes a number of further recommendations to prevent line infections.

To prevent infection, stringent cleaning of the catheter insertion site is advised. Povidone-iodine solution is often used for such cleaning, but chlorhexidine appears to be twice at good as iodine.cite journal |author=Mimoz O, Villeminey S, Ragot S, "et al" |title=Chlorhexidine-based antiseptic solution vs alcohol-based povidone-iodine for central venous catheter care |journal=Arch. Intern. Med. |volume=167 |issue=19 |pages=2066–72 |year=2007 |month=October |pmid=17954800 |doi=10.1001/archinte.167.19.2066] Routine replacement of lines makes no difference in preventing infection.cite journal |author=Cobb DK, High KP, Sawyer RG, "et al" |title=A controlled trial of scheduled replacement of central venous and pulmonary-artery catheters |journal=N. Engl. J. Med. |volume=327 |issue=15 |pages=1062–8 |year=1992 |pmid=1522842 |doi=]

Other complications

Rarely, small amounts of air are sucked into the vein as a result as the negative intrathoracic pressure. If these air bubbles obstruct blood vessels, this is a known as an air embolism.fact|date=June 2008

Hemorrhage (bleeding) and formation of a hematoma (bruise) is slightly more common in jugular venous lines than in others.

Arrhythmia may occur during the insertion process when the wire comes in contact with the endocardium. It typically resolved when the wire is pulled back.fact|date=June 2008

References

External links

* [http://www.cancer.gov/Templates/db_alpha.aspx?CdrID=45962 National Cancer Institute: central venous access catheter]