Venous return disorders

Introduction The systemic venous tube delivers blood back to the right atrium. The systemic venous system has a large blood volume, accounting for more than half of the total blood. The vein is easily dilated and can contract, thus acting as a blood storage stock. The contraction and relaxation of the vein can effectively regulate the amount of blood return and cardiac output, so that the circulation function can adapt to the needs of the body in various physiological states. The basic force of venous return is the pressure difference between the venule (also known as the peripheral vein) and the vena cava or right atrium (also known as the central vein). An increase in venule pressure or a decrease in vena cava pressure is beneficial for venous return. Since the venous wall is thin and the venous pressure is low, the venous return is also affected by external force such as muscle contraction, respiratory motion, gravity, and the like. When the above factors hinder venous return, the body will exhibit various manifestations.

Cause

Myocardial contraction is weakened in right heart failure, blood incompleteness is caused, resulting in increased central venous pressure and venous return. Most of the primary mediastinal lymphoma and metastatic tumors are caused by malignant tumors. Superior vena cava thrombosis, etc. can also cause SVCS. When the superior vena cava reflow is not good, it will also lead to local circulation reflow obstacles.

an examination

Related inspection

Abdominal vein examination for jugular vein examination

Myocardial contraction is weakened in right heart failure, blood incompleteness is caused, resulting in elevated central venous pressure, venous return obstruction, most of which are caused by malignant tumors such as primary mediastinal lymphoma of the lung cancer and metastatic tumors, such as chronic mediastinal inflammation. Vascular thrombosis and the like can also cause SVCS. When the superior vena cava reflow is not good, it will also lead to local circulation reflow obstacles. The clinical manifestations depend on the degree of obstruction at the site of acute obstruction and the formation of collateral circulation. Usually, more than half of the insidious onset has a history of 2 to 4 weeks, and special symptoms and signs are common. The most common symptom is dyspnea with facial edema. For the trunk and upper extremity edema, chest pain, cough, difficulty in ingestion, such as secondary intracranial pressure, can occur in the central nervous system symptoms, physical examination, thoracic jugular vein dilatation, facial edema, shortness of breath, and may also have facial redness, upper extremity cyanosis and edema. (or) Horner syndrome. At this time, it is necessary to check the B-ultrasound and physical examination. If necessary, the vena cava cannulation can be performed for a clear diagnosis.

Differential diagnosis

The enhancement of myocardial contractility can make the blood in the heart chamber more complete, thereby increasing the pressure difference between the small vein and the vena cava, and promoting venous return. When the right heart fails, myocardial contraction is weakened, blood is not complete, resulting in increased central venous pressure, venous return blocked, venous system congestion, jugular vein engorgement, hepatomegaly and lower extremity edema. Changes in intrathoracic negative pressure during respiratory exercise have a positive effect on the return of blood in the vena cava. In patients with severe pneumothorax, the reduction or disappearance of the negative pressure in the chest may cause an obstacle to the return of the body.

In the venous system, there are symptoms such as jugular vein engorgement, hepatomegaly and lower extremity edema.

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