What is a central venous access?
A central venous access (a.k.a. a central line or a central venous catheter) is a catheter placed into a patient and its tip advanced into a central vein. The right atrium, the superior and inferior vena cava, the subclavian veins, the brachiocephalic veins and the iliac veins are considered central veins.
Because large volumes of blood pass through these chambers or vessels per unit time, medications or nutrients, which are weak acids and bases with variable potential for damaging the venous wall, are quickly diluted and ‘flushed’ on when injected directly into the central veins. When they are used for hemodialysis, the capacity of these vessels is adequate for the high flow rates necessary for efficient dialysis and avoids the venturi effect that sucks venous wall into the catheter side holes and impedes dialysis.
The location of the vein where the catheter enters the body before journeying to the heart modifies its name. Thus, venous access through the jugular, subclavian, or femoral vein or the inferior vena cava is a centrally inserted central venous access (CICVA) or centrally inserted central catheter (CICC); when the insertion site is the cephalic or basilic vein or a deep vein of the arm, the access is called a peripherally inserted central catheter (PICC).
What happens to the trailing end of the catheter is equally important. It may be secured to the skin where it enters the vein and called a non-tunneled venous access, or burrowed beneath the skin for a variable distance before exiting unto the surface as a tunneled venous access.
The trailing end of the tunneled catheter may be attached to a hub and secured to the skin with sutures or other chic fasteners, and is called a tunneled catheter without a subcutaneous port, or connected to a reservoir (port) buried in a pocket fashioned beneath the skin, and is called a tunneled catheter with a subcutaneous port. (A port is a small hollow round container made with metal or plastic material and covered with rubber-like diaphragm. A small spout leads from its bottom and is the attachment for the catheter.) At use the subcutaneous port’s diaphragm is pierced through the skin ( this is called ‘accessing’) with a special non-coring needle called a Huber needle. A non-coring needle is preferred over other forms of needle because it does not destroy the diaphragm of the reservoir over time, whereas other needles chip it away over time allowing injectants to leak through it. The shaft of the tunneled catheter unattached to a port or pump is fitted with a cuff of collagen that reacts with the tissues beneath the skin to form a firm and durable bond that keeps the catheter from falling out.
The advantages of tunneled central venous accesses over non-tunneled accesses include less risk of infection, enhanced durability, and less risk of accidental or spontaneous explantation. Tunneled catheters attached to subcutaneous ports have the additional value of aesthetics: only the patient knows they exist because they are hidden by the skin.
Each of these catheters comes as a single-lumen or a double-lumen catheter and is usually ready for use immediately after its placement.
Who needs a central venous access?
In a general sense, if you need prolonged access into your veins for the administration of medications, fluids, or nutrients or frequent withdrawal of blood from you for various tests, it makes good sense to place a durable venous access in you early in your care, not after many days of needle sticks for the same purposes. Sometimes, however, the right time for such an intervention is unclear upon your admission to the hospital, but the earlier the decision is made the better it is for you. There are situations we know will invariably require long-lasting central venous access and they include hemodialysis for end-stage kidney failure; chemotherapy for various cancers; difficult-to-stick patients like those who have lost their veins through chronic injection of illicit drugs or those whose chronic ill-health has caused them their veins from frequent needle sticks like people with sickle cell disease.
Non-tunneled catheters are usable for up to three (3) months, if cared for well. Tunneled catheters can stay in patients even longer and are usually placed in those with chronic conditions that require prolonged venous access such as those on hemodialysis for kidney failure, or in patients whose treatment for their disease requires many cycles of intravenous injections.
Preparing for the placement of a central venous access
You do not need any special preparation for the placement of these lines or accesses, except perhaps the tunneled accesses. Many operators provide local anesthesia for the placement of a PICC line, whereas the placement of a tunneled access generally requires deep sedation, usually with a combination of an opiate and a benzodiazepine; such placement takes a slightly longer time and is a little more involved. For these reasons, standard of care requires that you avoid eating or drinking at least 8 hours prior to the procedure to prevent aspiration of your gastric contents into your lungs, because you lose your protective airway reflexes in deep sedation. It is important to prepare yourself mentally for the procedure.
How is a central venous access placed?
The method of placing a central venous access varies from operator to operator. In general, however, the technique requires strict attention to detail to reduce the risk of infection. Some institutions place PICCs at patients’ bedside, while others place all central venous accesses in a more controlled environment like an interventional radiology or surgical suite.
After receiving local anesthetic with or without deep sedation, the operator will identify and access a vein in the arm, the root of the neck, or the groin (depending on the patient’s condition, needs, and patency of veins, or the operator’s preference), guided by anatomic landmarks, palpation, or an imaging modality like ultrasound and fluoroscopy; fluoroscopy requires the injection of radiocontrast (dye) into a peripheral vein to opacify the veins in the arm. Then the catheter is introduced into the punctured vein and advanced centrally towards the heart. The hub of the catheter is then secured to the patient’s skin with sutures or, in the case of tunneled catheters, its trailing end is tunneled subcutaneously away from the venous puncture site and attached to a pump or port or is fitted with a hub.
What can go wrong during and after the placement of a central venous access?
The placement of a central venous access is relatively safe, but it is good to be aware of the following things that may go wrong:
1. The skin site may become infected several days, weeks, or months after the catheter placement or a system-wide infection may develop, also after a variable time.
2. The closeness of the tip of the catheter to the lining of heart chambers (the endocardium) may precipitate an infection of the lining (endocarditis) that evolves into a system-wide infection.
3. During the placement of the catheter a near-by artery or nerve may be unintentionally injured.
4. If the venous access is at the root of the neck or close to the chest wall, a patient may sustain a pneumothorax (the accumulation of air within the potential space around the lung) or hemothorax (the accumulation of blood within the potential space around the lung) from injury to the pleura (the covering membrane of the lung) or a nearby blood vessel or both. These two complications may develop rapidly or slowly and may threaten life if not detected and managed early.
5. The vein through which the catheter passes to the heart may thrombose (occlude with clot) and cause arm or neck swelling.
6. Rarely, patients suck air into their blood stream through the instruments used for the procedure. The sucking in of a small amount of air may be tolerated by the patient, but larger amounts may be catastrophic.
What are the contraindications to the placement of a central venous access?
There are not many contraindications to the placement of a central venous access, but the following apply:
1. The presence of systemic infection, which means whole-body infection.
2. The presence of severe coagulopathy (significant ‘thinning’ of the blood) that may cause the patient to bleed excessively during or after the procedure.
3. Lack of suitable veins.
4. If the patient does not want the procedure.
How to care for a central venous access
If the need for your access is immediate, you can use it right after its placement. You will be sore at the site of the procedure for a few days, but will do well with analgesics like acetaminophen (Tylenol). For the first few days keep your wound dry and clean and be in touch with your care giver. In some IR practices an IR nurse will call you within 24 hours of your procedure to check how you are doing. If the operator used non-absorbable sutures (these are made from materials that your body will not absorb over time) to close your wound, be sure he tells you when to return for their removal. Finally, keep a watchful eye on the catheter site and yourself and do not delay reporting to your provider early signs of local or system-wide infection such as new or persistent pain and redness at the wound site, seepage of foul fluid from the skin entry site, fever, chills, or a sense of not feeling well (malaise).
How long can a central venous access be used and how is it removed?
Excluding those catheters that are hurriedly placed in sick patients in the intensive care unit or the emergency department as part of the urgent life-saving measures that swirl around them at the beginning of the ill-health and are usually removed or changed within 7 days, most central venous accesses are durable. Some, like the dialysis catheter, may remain in the patient for years, if their condition demands continuous use of the catheter. Others are kept in for a few months. Most are removed from the patient when the need for them no longer exists because they are foreign bodies and potential nidus for setting up infection. The non-tunneled catheters are easily pulled out and bleeding at the insertion site controlled by a brief application of pressure. Removal of tunneled catheters requires dissecting them out through small skin incisions and generally is done in the interventional radiology suite or the operating room. The procedure is much quicker and a less harrowing emotional experience than the placement of the catheter.