Chorionic Villous Sampling
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In radiology, venous access generally refers to central venous access, which is the insertion of a specially made thin, flexible tube, known as a catheter, into a central vein. The central veins are the large veins within the chest and abdomen.
With a catheter in place, treatments such as chemotherapy or antibiotics can be given through the catheter over a period of time without the need for repeated injections. A catheter can also be used when regular blood samples need to be taken for blood transfusions and other medical conditions that need access to a vein over days, weeks or months.
For venous access, the tip of the catheter is usually placed within the superior vena cava, which is a large vein positioned just above the heart, or within the right atrium, which is a chamber within the heart receiving all blood from the body through the veins.
There are many different types of catheters available for venous access.
Peripherally-inserted central catheters (PICC) are inserted through a vein in the arm, with the tip placed within a central vein.
Non-tunnelled central catheters are inserted through a large vein, usually at the base of the neck (jugular or subclavian vein) or groin (femoral vein).
Tunnelled central catheters are inserted through a large vein, usually at the base of the neck (jugular vein). They travel for several centimetres under the skin surface (‘the tunnel’) before entering the vein. These catheters have a cuff, located in the tunnelled portion, that helps stimulate tissue growth and hold the catheter in place for several centimetres before exiting the skin. [See Fig 1]
Implantable ports are inserted in a manner similar to tunnelled central catheters, but instead of exiting the skin after several centimetres, they are connected to a reservoir or port, which is also placed under the skin. Both the port and the catheter are placed completely under the skin. The port has a silicon window and a needle can be inserted through the skin and into the silicon window to provide access to the port and catheter. [See Fig. 2]
Venous access is a medical procedure carried out in a hospital or private radiology practice, and your preparation will vary between different practitioners and hospitals or facilities.
You will usually be asked to fast (go without food or liquid) for 6 hours before the procedure. If you have diabetes and require insulin, you will need to adjust your insulin regimen accordingly. You will need to discuss this with your referring doctor.
You will need to inform your doctor or booking staff at the facility where you are having the procedure when you make your appointment whether you are taking any blood thinning medications, such as warfarin or aspirin, or have a blood clotting disorder. It may not be necessary to stop taking these medications, but this will vary between different facilities.
If you are having implantable ports, it is usually necessary to stop taking these medications a number of days before your procedure. If you have any blood clotting abnormalities or disorders, these may need to be corrected by injection of medications or agents that allow your blood to clot in a normal way. Your referring doctor or the radiology facility will advise you about this.
On the day of your procedure, ensure that you wear a loose-fitting top, because you will most likely be asked to change into a hospital gown. If you are having a tunnelled catheter or implantable port, you will need to remove necklaces, as these will be in the way of the venous access entry site at the base of the neck and increase the risk of infection.
Venous access is carried out in the angiography or fluoroscopy suite of a hospital or private radiology practice. This is a room specifically set up for this type of procedure with ultrasound and X-ray equipment.
You are placed on a special bed, usually positioned in or near the centre of the room. You may be given oxygen and medications to ease any pain and to make you a little drowsy, particularly if you will be having an implantable port or tunnelled catheter.
A large area of skin around the site of the venous access will be thoroughly cleaned with an antiseptic solution to minimise the risk of infection. Sterile drapes are used to cover other areas of your body, again to keep risk of infection to a minimum, leaving the site for venous access exposed.
Local anaesthetic is injected into your skin through a small needle to numb the skin at the site of venous access, but you will still be awake. If you are having a tunnelled catheter or implantable port, local anaesthetic is also injected into the proposed site of where the catheter or port will be inserted. The initial injection of local anaesthetic will sting, but the sensation will quickly pass as the local anaesthetic starts to work.
A small incision is made in your skin, usually in your mid upper arm for PICC lines or at the base of your neck for other catheters with the guidance of images or pictures on an ultrasound machine. A needle is then inserted through the small incision and into the underlying vein. After gaining access into the vein with the needle, X-ray images are used to guide (through this needle puncture) various specialised flexible wires and small plastic sheaths, followed by the venous access catheter itself, through the site of the needle puncture. The tip of the catheter is placed deep into the central vein and accurately positioned using X-ray images.
Very rarely, a contrast medium, which is a liquid ‘dye’ visible on X-ray, may be injected into the veins to outline them clearly. The contrast medium is used only if there is difficulty in accessing the veins. Any abnormalities or blockages in the veins will become visible with contrast medium.
If you are receiving a tunnelled catheter, a second small incision is made at the proposed skin exit site of the catheter, usually a few centimetres below the first incision site at the base of your neck.
A special plastic or metal device is used to create a very small tract or tunnel beneath your skin, extending between the two incision sites. The catheter is passed through this tunnel. Sutures (stitches) or firm adhesive tape may be used to secure the external portion of the catheter, which is outside your skin.
If you are receiving an implantable port, then in addition to the tunnel, a small pouch, just large enough to hold the port, is created beneath your skin. This pouch is positioned at the lower end of the tunnel and created using various specialised surgical instruments. The port is placed within the pouch, secured using sutures, and connected to the catheter.
Your newly inserted venous access catheter or port is tested to ensure it is working correctly. The catheter or port is then flushed with normal saline (salt water) and a special medication called heparin to prevent any blood within the catheter from clotting. All incisions are then sutured and firm adhesive dressings applied.
In most cases, there are no major after effects.
If you received medications to make you drowsy for the procedure, it may take a few hours before you become fully alert. You may be consciously aware of the presence of the catheter for a few days, but this sensation should quickly pass.
Occasionally, you may have some bleeding at the skin site where the procedure was carried out. If this occurs, it is usually within the first hour after the procedure. The bleeding can be easily treated by medical staff, either a doctor or nurse, by pressing on the site of bleeding for a few minutes.
The procedure usually takes approximately 30 minutes.
Venous access carried out in the angiography suite using ultrasound and X-ray guidance is a relatively safe procedure. Complications are rare and can be divided into those occurring during the procedure and those occurring afterwards.
Complications during the venous access procedure:
Venous access plays a major role in current medical practice where access to a vein is needed over a long period of time. Central venous catheters serve many purposes, including the delivery of medications (such as antibiotics, chemotherapy drugs and narcotics), administration of blood products, repeated taking of blood for testing, bone marrow transplant protocols, high-volume blood transfusions, giving intravenous fluids and any administering of medications normally given by injection.
Once the catheter has been inserted, medications can be administered painlessly over a long period of time and prevent scarring that can occur with repeated puncturing of the vein. Catheters can remain in place for a year or more and can be easily removed once the need to access the vein has passed.
This is usually carried out by a radiologist, who is a specialist doctor trained to do these procedures, and known as an interventional radiologist. At some hospitals, specialised clinical nurses may also be trained to insert PICC lines. Trained medical technologists (sonographer or radiographer) will also be present to operate the ultrasound and X-ray equipment, and depending on where you are having the procedure done, there may also be nursing staff present.
The procedure is carried out in an angiography suite in a hospital or private radiology practice. This is a room specifically set up for this type of procedure, with X-ray and ultrasound machines to provide real-time images or pictures to ensure the needles, wires and catheter are accurately placed. There is also monitoring equipment, trained medical staff and medications to ensure your procedure is carried out comfortably and safely.
After your venous access catheter is inserted, it is ready for immediate use. Dressings should be changed the next day. If there are sutures, they can be removed in 1 week. The maintenance and care of each catheter is specific to the type and brand of catheter. You will be provided with an information sheet or booklet with this information, specific to your catheter.
Page last modified on 30/8/2018.
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