Arteriovenous fistula
Encyclopedia
An arteriovenous fistula is an abnormal connection or passageway between an artery
and a vein
. It may be congenital, surgically created for hemodialysis
treatments, or acquired due to pathologic
process, such as trauma
or erosion of an arterial aneurysm
.
Patients with end stage renal failure are treated with hemodialysis
. In dialysis, blood is withdrawn from an artery or vein, purified, and returned to a vein. The volume of blood is too great for veins to handle, so a vein must be enlarged. An artery and vein, usually in the arm above or below the elbow, are sewn together, to create a fistula
, and arterial pressure eventually enlarges the vein. The enlarged vein can accommodate a cannula
or large needle.
, it can lead to a large decrease in peripheral resistance. This lowered peripheral resistance causes the heart to increase cardiac output
to maintain proper blood flow to all tissues. The physical manifestations of this would be a relatively normal systolic blood pressure
with a decreased diastolic blood pressure resulting in a wide (large) pulse pressure
.
Normal blood flow in the brachial artery
is 85 to 110 milliliters per minute (mL/min). After the creation of a fistula, the blood flow increases to 400 to 500 mL/min immediately, and 700 to 1,000 mL/min within 1 month. A bracheocephalic fistula above the elbow has a greater flow rate than a radiocephalic fistula at the wrist. Both the artery and the vein dilate and elongate in response to the greater blood flow and shear stress, but the vein dilates more and becomes "arterialized". In one study, the cephalic vein
increased from 2.3 mm to 6.3 mm diameter after 2 months. When the vein is large enough to allow cannulation, the fistula is defined as "mature."
An arteriovenous fistula can increase preload.
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
and a vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
. It may be congenital, surgically created for hemodialysis
Hemodialysis
In medicine, hemodialysis is a method for removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure. Hemodialysis is one of three renal replacement therapies .Hemodialysis can be an outpatient or inpatient therapy...
treatments, or acquired due to pathologic
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
process, such as trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
or erosion of an arterial aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
.
Vascular access for hemodialysis
Hemodialysis
In medicine, hemodialysis is a method for removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure. Hemodialysis is one of three renal replacement therapies .Hemodialysis can be an outpatient or inpatient therapy...
. In dialysis, blood is withdrawn from an artery or vein, purified, and returned to a vein. The volume of blood is too great for veins to handle, so a vein must be enlarged. An artery and vein, usually in the arm above or below the elbow, are sewn together, to create a fistula
Cimino fistula
A Cimino fistula, also Cimino-Brescia fistula, surgically created arteriovenous fistula and arteriovenous fistula , is a type of vascular access for hemodialysis...
, and arterial pressure eventually enlarges the vein. The enlarged vein can accommodate a cannula
Cannula
A cannula or canula is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of data...
or large needle.
Physiology
When an arteriovenous fistula is formed involving a major artery like the abdominal aortaAbdominal aorta
The abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta .-Path:...
, it can lead to a large decrease in peripheral resistance. This lowered peripheral resistance causes the heart to increase cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
to maintain proper blood flow to all tissues. The physical manifestations of this would be a relatively normal systolic blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
with a decreased diastolic blood pressure resulting in a wide (large) pulse pressure
Pulse pressure
Pulse Pressure is most easily defined as being the amount of pressure required to create the feeling of a pulse. Measured in millimeters of mercury , the pressure difference between the systolic and diastolic pressures give you the amount of pressure change to create the pulse, which is the pulse...
.
Normal blood flow in the brachial artery
Brachial artery
The brachial artery is the major blood vessel of the arm.It is the continuation of the axillary artery beyond the lower margin of teres major muscle. It continues down the ventral surface of the arm until it reaches the cubital fossa at the elbow. It then divides into the radial and ulnar arteries...
is 85 to 110 milliliters per minute (mL/min). After the creation of a fistula, the blood flow increases to 400 to 500 mL/min immediately, and 700 to 1,000 mL/min within 1 month. A bracheocephalic fistula above the elbow has a greater flow rate than a radiocephalic fistula at the wrist. Both the artery and the vein dilate and elongate in response to the greater blood flow and shear stress, but the vein dilates more and becomes "arterialized". In one study, the cephalic vein
Cephalic vein
In human anatomy, the cephalic vein is a superficial vein of the upper limb.It communicates with the basilic vein via the median cubital vein at the elbow and is located in the superficial fascia along the anterolateral surface of the biceps brachii muscle.Superiorly the cephalic vein passes...
increased from 2.3 mm to 6.3 mm diameter after 2 months. When the vein is large enough to allow cannulation, the fistula is defined as "mature."
An arteriovenous fistula can increase preload.
See also
- Branham sign
- FistulaFistulaIn medicine, a fistula is an abnormal connection or passageway between two epithelium-lined organs or vessels that normally do not connect. It is generally a disease condition, but a fistula may be surgically created for therapeutic reasons.-Locations:Fistulas can develop in various parts of the...
- Cimino fistulaCimino fistulaA Cimino fistula, also Cimino-Brescia fistula, surgically created arteriovenous fistula and arteriovenous fistula , is a type of vascular access for hemodialysis...
- HUVG
- Carotid-cavernous fistulaCarotid-cavernous fistulaA carotid-cavernous fistula results from an abnormal communication between the arterial and venous systems within the cavernous sinus in the skull. It is a type of arteriovenous fistula...
External links
- Arteriovenous Fistula at Merck Manual
- Overview at Mayo ClinicMayo ClinicMayo Clinic is a not-for-profit medical practice and medical research group specializing in treating difficult patients . Patients are referred to Mayo Clinic from across the U.S. and the world, and it is known for innovative and effective treatments. Mayo Clinic is known for being at the top of...