arteriovenous shunt


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Related to arteriovenous shunt: Arteriovenous malformation

shunt

 [shunt]
1. to turn to one side; to divert; to bypass.
2. a passage or anastomosis between two natural channels, especially between blood vessels. Such structures may be formed physiologically (e.g., to bypass a thrombosis), or they may be structural anomalies.
3. a surgical anastomosis.
arteriovenous shunt a U-shaped plastic tube inserted between an artery and a vein (usually between the radial artery and cephalic vein), bypassing the capillary network, a formerly common means of arteriovenous access.
cardiovascular shunt an abnormality of the blood flow between the sides of the heart or between the systemic and pulmonary circulation; see left-to-right shunt and right-to-left shunt.
jejunoileal shunt an intestinal bypass performed to control obesity.
left-to-right shunt diversion of blood from the left side of the heart to the right side, or from the systemic to the pulmonary circulation through an anomalous opening such as a septal defect or patent ductus arteriosus.
LeVeen shunt peritoneovenous shunt.
mesocaval shunt a portosystemic shunt between the superior mesenteric vein and the inferior vena cava to reduce portal hypertension.
peritoneovenous shunt a device whose purpose is to remove excess ascitic fluid from the peritoneal cavity and return it to the venous system; called also LeVeen shunt.



The shunt consists of a peritoneal tube, a one-way valve, and a tube leading to a large vein, usually the superior vena cava or the jugular vein. The perforated peritoneal tube is placed in the peritoneal cavity and attached to the one-way valve which opens at a pressure of 3 cm H2O. The valve controls the direction of the flow of ascitic fluid and prevents a backflow of blood from the vein. A tube leading from the valve empties into the venous system.

The shunt is triggered into action by the patient's breathing. Upon inspiration, the diaphragm descends toward the abdominal cavity and causes a rise in fluid pressure in the thoracic superior vena cava. The difference in pressure, usually about 5 cm H2O, opens the shunt valve, allowing the flow of ascitic fluid into the large vein. The action of the shunt can be enhanced by the patient's inspiring against pressure, as when using a blow bottle.

A disadvantage of the shunt is dilution of the blood and a resultant drop in hematocrit, which necessitates transfusion of packed cells and perhaps a slowing of the rate of flow of ascitic fluid into the venous system. Other inherent risks are infection, leakage of ascitic fluid from the operative site, elevated bilirubin, gastrointestinal bleeding, and disseminated intravascular coagulation.
Peritoneovenous (LeVeen) shunt for chronic ascites moves fluid from the peritoneal (abdominal) cavity into the superior vena cava. From Ignatavicius and Workman, 2000.
portacaval shunt a portosystemic shunt between the portal vein and the vena cava.
portosystemic shunt a surgically created shunt that connects the portal and systemic circulations, such as a mesocaval, portacaval, or splenorenal shunt.
postcaval shunt portacaval shunt.
pulmonary shunt an anomaly in which blood moves from the venous circulation to the arterial circulation without participating in gas exchange, resulting in hypoxemia.
reversed shunt right-to-left shunt.
right-to-left shunt diversion of blood from the right side of the heart to the left side or from the pulmonary to the systemic circulation through an anomalous opening such as septal defect or patent ductus arteriosus.
splenorenal shunt an anastomosis of the splenic vein and the left renal vein, created to lower portal hypertension following splenectomy.
ventriculoatrial shunt the surgical creation of a communication between a cerebral ventricle and a cardiac atrium by means of a plastic tube; done for relief of hydrocephalus.
ventriculoperitoneal shunt a communication between a cerebral ventricle and the peritoneum by means of plastic tubing; done for the relief of hydrocephalus.
ventriculovenous shunt a communication between a lateral ventricle and the venous system by means of a plastic tube; done for relief of hydrocephalus.

ar·te·ri·o·ve·nous shunt (A-V shunt),

the passage of blood directly from arteries to veins, without going through the capillary network.

arteriovenous shunt (AV shunt)

a passageway, artificial or natural, that allows blood to flow from an artery to a vein without going through a capillary network.

arteriovenous shunt

Arteriovenous fistula Therapeutics The surgical joining of an artery and a vein under the skin to create a hemodialysis access port Complications Large AVSs cause cardiac overload as arterial blood passes to the venous circulation without delivering nutrients and O2 to tissues

ar·te·ri·o·ve·nous shunt

(ahr-tēr'ē-ō-vē'nŭs shŭnt)
The passage of blood directly from arteries to veins, without going through the capillary network.

arteriovenous shunt

; AVS sphincteric mechanism controlling capillary bed blood flow: when the AVS is closed (i.e. the controlling sphincter is constricted) blood flows through the capillary bed; when the AVS is open (i.e. the controlling sphincter is relaxed) blood is diverted away from and largely bypasses the capillary bed; sphincter sympathetic control is lost as part of diabetic neuropathy, and AVSs remain open inappropriately, with resultant reduced skin capillary perfusion and superficial ischaemia, and increased flow through deeper tissues, especially bone, exacerbating the tendency to Charcot neuroarthropathy; see sign, Ward's

ar·te·ri·o·ve·nous shunt

(ahr-tēr'ē-ō-vē'nŭs shŭnt)
The passage of blood directly from arteries to veins, without going through the capillary network.
References in periodicals archive ?
Stewart-Bluefarb syndrome is characterized by congenital arteriovenous malformation of the lower extremity accompanied by multiple arteriovenous shunts and an early onset age.
2) Angiography shows a highly vascular lesion with enlarged feeding arteries, arteriovenous shunts, and delayed washout.
These include arteriovenous shunts, giving rise to congestive heart failure, bleeding diathesis due to platelet consumption, and massive hemoperitoneum resulting in rupture.
TEVGs could also potentially serve as arteriovenous shunts for patients undergoing dialysis.
Acroangiodermatitis (pseudo-Kaposi sarcoma) is a dermatological condition characterized by purple-colored nodules, plaques or patches, mostly on the extensor surfaces of lower extremities, usually in patients with chronic venous insufficiency and arteriovenous malformations of the legs, but also in hemodialysis patients with iatrogenic arteriovenous shunts, paralyzed limbs and amputation stumps.
In the early days all patients had arteriovenous shunts.
Treatments were 6 hours each using large dialysis machines and coils; reuse was a common practice to contain costs; there was no water treatment; dialysate fluid contained acetate as a buffer and no dextrose; and arteriovenous shunts were the only kind of access available.
Francis described erythromelalgia as a "mysterious condition" in which an increase in blood flow and temperature in the extremities strangely corresponds to a decrease in tissue oxygenation due to dysfunctions of the precapillary sphincters and arteriovenous shunts, said Dr.
This problem commonly occurs after angioplasty, bypass surgery and within arteriovenous shunts.
2) suggested that local venous hypertension opens up the normally closed arteriovenous shunts and arterial blood reaches the venous channels bypassing the capillary circulation.
Access was primarily provided via arteriovenous fistulae with a fair number of arteriovenous shunts thrown in for good measure.