What is a Central Line
A central line is a type of catheter that is placed in a large vein. When compared to a typical IV line, a central line is larger, can stay in place longer, can deliver a greater volume of fluids and allows blood to be drawn easily. A central line can also be used to measure fluid volume status, and to help determine if a patient is dehydrated or has received an adequate amount of fluid to support bodily functions.
Why Is a Central Line Used
A central line may be placed for multiple reasons. A central line may have up to 5 lumens, which are ports in which fluid can be infused, blood can be drawn or measurements may be taken. If a patient needs fluid resuscitation, meaning large amounts of intravenous fluids need to be given, a central line may be placed to allow fluid to flow faster.
Central lines can be used to draw blood as well. In some cases, two of the lumens on the central line can be used to perform dialysis, with one lumen used to take blood out of the vascular system and another lumen used to return the dialyzed blood to the body. For patients who require frequent blood draws to be sent to the laboratory, the central line allows for blood to be drawn without repeatedly "sticking" the patient.
One function that is unique to some central lines is the ability to measure a central venous pressure. This measurement gives the healthcare team insight into how much fluid is in the vascular system, and if the patient has received too much or too little fluid. If the central line is a Swann-Ganz type catheter, a pulmonary wedge pressure can also be obtained, which can indirectly indicate how the left atrium of the heart is functioning.
A central line is also appropriate when long term therapy is expected, such as weeks of IV antibiotic treatment, or if caustic medications are needed that cannot be given through a standard IV, such as chemotherapy.
Insertion of a Central Line
In order to insert a central line, the patient must be lying flat, and the area of the body where the central line will be inserted is exposed. The most common veins used for placement of a central line are the internal jugular in the neck, the subclavian vein near the clavicle, and the femoral vein in the groin.
The patient is covered, typically from head to toe, with a sterile drape. The drape is a sterile paper sheet with a hole in it to allow the individual placing the central line access to the vein. The sterile drape is intended to help reduce the risk of infection, and studies have shown that covering the entire body, rather than just the area where the central line will be placed, is the best practice for the prevention of infection.
Once the patient is draped, the area of skin is cleaned. If the patient is awake, the area of skin may also be numbed with a local anesthetic. Using sterile technique, a hollow catheter is then inserted into the vein, typically using ultrasound to locate the appropriate blood vessel. The catheter is then stitched in place, or an adhesive device is used to hold the catheter still at the insertion site.
The area is then cleaned again with antiseptic and a sterile dressing is placed over the insertion site, with the lumens accessible. Placement of the catheter must be confirmed using an x-ray before the central line can be used, to avoid accidentally infusing medications into tissue or the wrong blood vessel. In some cases, the catheter may be in the correct vessel, but need slight adjustment because the catheter is either too far in the vessel or not quite far enough.
Central Line Associated Bloodstream Infection (CLABSI)
One of the risks of central line placement and usage is a bloodstream infection. To help prevent infections, standardized best practices have been implemented. These practices include scheduled sterile dressing changes, the use of a full body sterile drape during placement of the line, removing the line as soon as it is no longer necessary, and only inserting central lines that are absolutely necessary.
Central lines are typically placed above the waist when possible to minimize the risk of infection. Femoral vein sites are associated with higher rates of infection. The dressing placed over the insertion site is typically clear, which allows the healthcare team to check for signs of infection without exposing the insertion site to air more than absolutely necessary.
Risks of a Central Line
There are risks associated with the insertion of a central line, which must be weighed against the patient's need for the line. Infection is the greatest risk of a central line, with other risks including pneumothorax (collapsed lung), particularly if the central line is placed in the subclavian vein, which is treated with a chest tube when necessary.
During the insertion of some types of central lines, the heart may be irritated by the process, causing an alteration in the heart's rhythm. This typically resolves with appropriate placement of the line.
One final complication of central lines is an air embolism, a condition where air enters the vascular system and begins to travel through the body. This condition, which is very serious, is also very rare and largely preventable.
Central Line Associated Bloodstream Infection. California Department of Health. Accessed March, 2013. http://www.cdph.ca.gov/programs/hai/Pages/CentralLine-associatedBloodStreamInfection(CLABSI).aspx