Vascular access describes a process of setting up a method for either removing blood from the body, for example where blood needs to be filtered by a dialysis machine for patients with kidney failure or end-stage renal disease, or for delivering medication into the bloodstream, for example during chemotherapy for patients with cancer.
Vascular access allows blood or chemicals to be removed or introduced much more quickly than would be possible via normal intravenous methods. There are four types of vascular access methods:
- Fistula
- Graft
- Catheter
- Portacath
Fistula
Using a procedure developed in 1966 and named after the inventors, Drs Cimino and Brescia, the 'Cimino-Brescia' fistula, this method involves creating an artificial fistula.
A fistula is a medical term (it is derived from the Latin word for 'tube') that describes an abnormal connection between two parts of the body, often between blood vessels or between sections of the intestines.
Generally, a fistula is a medical condition, but for vascular access the artificially created fistula, created between an artery and a vein (normally in the forearm) allows blood flow to increase so that a dialysis machine can process blood faster.
This method is also referred to as an 'arteriovenous fistula', 'primary AV fistula', 'AV fistula' or simply 'AVF'.
Graft
An arteriovenous graft (or 'synthetic bridge graft') is another way of connecting an artery and a vein as above, although the technique is slightly different, using a graft to connect them together instead of creating a fistula. The graft is a medical grade plastic tube.
Catheter
A 'venous catheter' or 'central venous catheter' is a form of tube placed into a vein, located either in the leg/groin area or the chest or neck. This method is used primarily for urgent short term dialysis where a patient may not have time to develop a fistula or graft.
Catheters are less suitable for long term use as they are more prone to blood clots or infection than either of the other methods, although they are another way of allowing vascular access for patients who are unable to have either an AV fistula or a graft.
An AV fistula is generally preferred to both the graft method and the catheter method as it lasts a lot longer (7+ years, in fact there are some on record in the US lasting for 35 years, compared to 2-3 years for a graft) and is less prone to infection and blood clotting.
Portacath
A portacath (sometimes simply referred to as a 'port') is a small device inserted under the skin on the upper part of the chest. It is implanted for people who need regular infusions of medication over a long period of time, normally as part of immunoglobulin or chemotherapy treatment.
The device itself is made up of a 'port' section, also referred to as the 'reservoir' (made of titanium), which sits just under the skin, and a tube (catheter) that connects the port to the internal jugular vein, a large vein located in the lower part of the neck.
The placement of the catheter ensures that drugs are delivered directly into the vein - this is important particularly for chemotherapy as some chemotherapy drugs are toxic - the portacath ensures these drugs do not have to travel through other blood vessels and are diluted by the blood flow in the major artery and from there carried effectively throughout the body.
Drugs are administered through a self-sealing silicone rubber membrane, which is designed to be punctured up to a thousand times before needing to be replaced. This is generally sufficient for treatments over several years.
Since there is only a small metal component and all other components are internal, showering, taking a bath and swimming are all possible after a portacath insertion. It generally does not set off metal detectors (for example at airports) although some people carry an explanatory card with them for officials and security personnel.
More information on vascular access: