Why a Central Line?
Infusions of chemotherapy drugs, antibiotics, anti-nausea medications, blood products, and fluids are an important part of the stem-cell transplant process. Many of these infusions would irritate the vein, and cause severe pain if administered into a smaller vein on the hand or arm. These infusions should be delivered into a big vein, where the infused drug gets mixed (and diluted) immediately with rapid-flowing blood. In addition, blood tests are drawn at least once a day. To allow these blood draws and infusions, a good access to the blood stream in a big vein is necessary. In order to avoid repeated venous sticks, a more permanent access to the central venous blood stream will be established. This can be done either at the bedside, or in the operating room. All these methods of access to a big "central" vein are called "central lines".
What Type of Central Line?
The simplest form of central line is the "triple lumen catheter", also called "subclavian line", which is inserted at the bedside into the subclavian vein that runs behind the clavicle. This catheter, which is quite thin, but still has three separate tubes (lumens) combined into one catheter (hence the name triple lumen catheter), allows rapid access to the blood stream. The catheter is inserted through the skin straight into the subclavian vein; it is simple to place, but not very well protected from infection. Most physicians believe that these catheters should be replaced every 5-7-days, because otherwise the risk of infection becomes too high. Attempts have been made to prolong the longevity of the catheter by coating the outside with antibiotics.
The HICKMAN® catheter is softer than a simple triple-lumen catheter, and is usually inserted in an operating room. The actual access to the subclavian vein is still by puncture under the clavicle, but the distal end of the catheter is pulled under the skin for 2-4 inches and comes out of the chest close to the nipple. This creates a "tunnel" which decreases the risk of infection. The HICKMAN® catheter, which is made of silastic (a silicone elastomere), comes in double-lumen and triple-lumen varieties. These catheters can stay in place for weeks to months; some patients have had the same HICKMAN® catheter for years!
The GROSHONG® catheter is very similar to the HICKMAN® catheter, but has a valve at the tip of the catheter which makes it unnecessary to leave a high concentration of heparin in the catheter (see below). The BROVIAC® catheter is also similar to the HICKMAN® catheter, but is of smaller size. This catheter is mostly used for pediatric patients.
Pheresis catheters are larger and sturdier than HICKMAN® catheters. Pheresis catheters can also be used for hemodialysis, and are often called "dialysis catheters". The HICKMAN® catheters are not designed to handle high-flow blood withdrawals; they are so soft that the walls of the catheter collapse (pull vacuum) when the dialysis, or pheresis, machine attempts to pull blood into the machine (see also Apheresis). These dialysis/pheresis catheters can either be inserted without a tunnel (e.g., Arrow Catheter®) at the bedside, or with a tunnel (e.g., PermCath®) in the operating room. Such tunneled pheresis catheters can serve both for the collection of stem cells and for support of the patient during the transplant episode.
The line (Peripherally Inserted Central Catheter) is inserted into one of the large veins in your arm near the bend of the elbow. The PICC line can be placed by a specially trained nurse or physician and is often inserted in the Radiology Department, but it can also be inserted at the bedside. A PICC line can stay in place for several weeks, but typically needs replacement earlier than a Hickman catheter or implantable port.
Implantable Ports are catheters which are inserted completely under the skin. The distal end of the catheter is formed by a small metal "drum" or reservoir, which has on one side a membrane for needle access. This drum is surgically placed under the skin, just below the clavicle, with the membrane immediately below the skin. The catheter runs from the drum into the subclavian vein. Access is always with a special needle that is pushed through the skin and the membrane into the reservoir inside the drum. Such ports come in different sizes, and can have either one or two lumens. Since the entire catheter is under the skin, the risk of infection is smaller than with external catheters.
How to Care for the Central Line?
Nearly every center has its own approach to care for their catheters. Often the differences are small, and probably insignificant. For a patient who wants to do everything as precise as possible, however, these differences may be very frustrating. It should be recognized that the lack of consistency between centers indicates that there are probably many good and appropriate ways to care for the catheter. Consistency within a center is more important than consistency between centers. A patient should learn to take care of his/her catheter in a certain way, and then stick with that approach to avoid errors and feelings of uncertainty.
Most centers will cover the exit site of the catheter, at least for the first weeks after placement. That cover (or dressing) may be gauze, a transparent plastic film, or a special pad. Such covers need to be replaced regularly, but how often varies markedly between centers. At IBMT, we do dressing changes three times a week while the patient is neutropenic, and twice a week thereafter. The dressing change includes taking off the old cover, cleaning the area around the exit site, and putting a new cover on. Patients are taught to do this in a way that carries a minimal risk of infection. Implantable ports do not have an exit-site, and therefore do not need to be covered.
Most catheters need to be flushed to reduce the risk of clotting inside the catheter. Ports are typically flushed at least once a month, and HICKMAN® catheters at least once a week. At the end of the flush, heparin is installed into the lumen of the catheter, and remains there until the next blood draw or flush.
What about Complications?
The main risk associated with central lines is infection. Anytime a foreign body dwells inside the blood vessel, an increased risk of infection exists. Catheters that come outside the body have an ever higher chance of becoming infected. Most of these infections are caused by skin bacteria (such as coagulase-negative Staphylococci), but other bacteria, and even yeasts and fungi, may also cause line infections. Attempts will be made to clear the infection with antibiotics, but often the catheter will have to be pulled (or replaced) to completely get rid of the infection.
Clotting inside the catheter, or outside around the catheter tip, may cause blockage of the catheter lumen. This may make it impossible to draw blood from the catheter, or even to flush it or use it for infusion. Heparin and other chemicals may be tried to clear the blockage, but occasionally that does not help and the catheter needs to be replaced.
Just as with any foreign object inside the blood vessel, intravenous catheters cause an increased risk of obstruction of the blood vessel. The formation of clots around the catheter is usually responsible for the obstruction. Typically, when the subclavian vein is obstructed, the arm will swell and be warm and tender. Removal of the catheter often restores the blood flow.
Patients learn to appreciate their catheters, since they will be subjected far less to blood draws by venipuncture. They will also not have an arm immobilized for hours or days, as is the case with intravenous infusions into an arm vein. The catheter should be cared for with a lot of consistency and attention to detail. The catheter truly becomes the "life-line" during the transplant process. If you have any concerns or questions about your central line, do not hesitate to discuss with your physician or nurse.
*BROVIAC, HICKMAN & GROSHONG are registered trademarks of C.R. Bard, Inc, and its related company, BCR, Inc.