Central venous catheters

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, chest or groin, this is inserted by a physician when the patient needs frequent or intensive cardiovascular monitoring, for assessment of fluid status, and for increased viability of intravenous drugs/fluids. The most commonly used veins are the internal jugular vein, the subclavian vein and the femoral vein. This is in contrast to a peripheral line which is usually placed in the arms or hands. The Seldinger technique is generally employed to gain central venous access. Examples of these devices include 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require clamps to make sure the valve is closed, and Groshong catheters, which have a valve that opens as fluid is withdrawn or infused and remains closed when not in use.

This device avoids the need for separate needle insertions into a vein for each infusion or blood test, although each infusion or test generally will require a separate needle insertion through the skin.



Description
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.

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 patent and prevents infection.

Indications and uses
Indications for the use of central lines include:
 * 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
 * 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.

Complications
Potential complications include:

Pneumothorax
Pneumothorax (for central lines placed in the chest) - this is why doctors routinely order a chest X-ray (CXR) after insertion of a subclavian or internal jugular line. 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%.

Infection
All catheters can introduce bacteria into the bloodstream, but CVCs are known for occasionally causing Staphylococcus aureus and Staphylococcus epidermidis sepsis.

Diagnosis
A patient with a central line, fever, and no obvious cause of the fever may have catheter-related sepsis. A meta-analysis found "Paired quantitative blood culture is the most accurate test for diagnosis of IVD-related bloodstream infection. The cultures are compared for number of colonies with line infection indicated by 5:1 ratio (CVC versus peripheral). However, most other methods studied showed acceptable sensitivity and specificity (both >0.75) and negative predictive value (>99%)".

Quantitative cultures are not commonly available. Alternatively, paired qualitative cultures in which time to positivity is assessed with line infection indicated by cultures that are positive 2 hours before peripheral cultures.

This analysis did not include gram stain and acridine-orange leucocyte cytospin test (AOLC) of 100 microliters of catheter blood (treated with edetic acid) which one group of investigators proposes.

The American Centers for Disease Control and Prevention recommends against routine culturing of central venous lines upon their removal, despite the additional information that may be acquired. However, the three cited studies do not directly address the validity of this practice.

Treatment
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.

Prevention
In order to reduce the risk of infection, stringent cleaning of the catheter insertion site is advised. Povidone-iodine solution is often used for such cleaning, but one study has found that chlorhexidine is better for this purpose, as it can prevent as much as 50% of all catheter colonisations.

To prevent infection, some central lines are now coated or impregnated with antibiotics, silver (specifically silver sulfadiazine) and/or chlorhexidine.

A randomized control trial found that routine replacement of a new central line catheter does not help.

Clinical practice guidelines from the American Centers for Disease Control and Prevention make a number of recommendations.

Arrhythmia
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.
 * Arterial injury

Confirmation
Except in emergent conditions, confirmation will be performed to ensure proper placement. Sonography and radiography are used most often to confirm placement.