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 ?
Those conditions included connective tissue disease, congenital heart disease, chronic thromboembolic disease, portopulmonary disease, severe lung disease, high-output arteriovenous shunts, and left-sided valve disease.
54) Coil embolotherapy was successful in a patient with large pulmonary arteriovenous shunts who underwent orthotopic liver transplantation for autoimmune hepatitis, but her symptoms failed to improve postoperatively.
These include arteriovenous shunts, giving rise to congestive heart failure, bleeding diathesis due to platelet consumption, and massive hemoperitoneum resulting in rupture.
There is some evidence for the existence of arterial structures among venules, which may suggest the presence of arteriovenous shunts (3).