Peripheral Vasculature in Health and Disease 2, Venous Aspects Flashcards
Describe veins
- Three layers
- Thin walled
- Large expandable lumen
- Not so circular
- Low pressure
- Valves
Describe small vein tributaries
Veins in the hand and foot, kidneys, brain, eye
Describe medium veins
Mesenteric, renal, femoral, popliteal, tibial, subclavian, brachial
Describe large veins
Vena cava, great veins in chest, iliac
How can blood drain by many routes?
- Many anastomoses
- Collateral circulation can compensate for occlusion of the main system in almost all circumstances
Describe how venous return works
- Muscle pumps
- Thoracic pump action during respiration
- Gravity- lying down
- Right heart function
- Requires functioning competent valves
Describe the venous reservoir
-High capacitance system
-64% of the total systemic circulation is within the veins
=18% in large veins
=21% in large venous networks such as liver, bone marrow
=25% in venules and medium sized veins
What is venous insufficiency?
- Failure of the muscle pump (typically calf muscle)- immobility, dependency, fixed ankle, loss of muscle mass
- Failure of valves
- Both
How are the normal Starling forces disrupted in venous hypertension?
Affects blood pressure- 35 mmHg in arterial end vs 25 mmHg in venule end (should be 16) due to high venous pressure
Describe venous hypertension
- Hemosiderin straining
- Swollen legs
- Itchy, fragile skin
- “Gaiter” distribution (shin pad)
- Risk of ulceration
What is the treatment for venous hypertension?
- Emollient to stop skin cracks
- Compression (bandages, wraps, stockings)
- Elevate and mobilise
What does valve failure lead to?
- Superficial veins= Varicose veins
- Deep veins= venous hypertension
What is the treatment for valve failure?
- Superficial veins= endothermal ablation, surgical removal, foam sclerotherapy, adhesive occlusion, compression
- Deep veins= compression
How does Virchow’s Triad link to venous thrombosis?
- Coagulopathy (blood)
- Stasis/ turbulence (flow)
- Endothelial abnormality (wall)
Where does Deep Venous Thrombosis occur?
Typically pelvic/ leg veins but can be axillary/ subclavian upper limb DVT
What are the risk factors for DVT?
Over 60 Overweight Smoker Previous DVT Contraceptive pill Cancer Heart failure
What is Phlegmasia and Venous Gangrene?
Rare, often with underlying cancer, thrombolysis
results from extensive thrombotic occlusion (blockage by a thrombus) of the major and the collateral veins of an extremity
How is DVT managed?
Anticoagulation Standard management Recannalisation can occur Valve damage allows reflux Not a major issue if calf vein DVT Problem if iliac vein Post thrombolytic limb syndrome
Describe superficial thrombophlebitis
Minor trauma Usually underlying varicose veins Symptomatic treatment Heparin to stop propagation Consider treating varicose vein
Describe the porto-systemic venous system
- Mesenteric or portal venous drainage is via the liver before the heart
- Systemic circulation is returned to the heart directly
- The two circulation systems combine a number of points
What is Porto-systemic venous anastomosis?
In liver disease the portal system fails to drain and porta; hypertension develops
Blood is therefore diverted into systemic venous system
collateral communication between the portal and the systemic venous system
What dilated systemic veins are caused by portal hypertension?
Oesophageal varices
Caput Medusa
How can veins be summarised?
- Veins are low pressure and rely on valves to ensure drainage
- Venous insufficiency can be failure of muscle pump or valves or both
- Venous thrombosis is determined by Virchow’s triad
- The portal venous system has anastomoses with the systemic venous system
Describe the lymphatic system
- Three layers- adventia, media, intima
- Capillary structure
- Valves like veins
- Many anastomoses
- Drain to lymph nodes
- Ultimately drain to thoracic duct
- Thoracic duct empties to left subclavian vein
What is lymphoedema?
Blocked lymphatic channels= interstitial fluid accumulates
What is the worldwide most common cause of lymphoedema?
Filariasis- parasitic disease caused by roundworms and their larvae
What is the treatment for lymphoedema?
- Compression
- Skin care
- Exercise
- Manual lymphatic drainage- specialised massage technique
- Rarely surgery to debulk, liposuction or connecting lymph channel to veins
How can lymphatics be summarised?
- Low pressure, mesh-like system
- Valves like veins
- Drain into lymph nodes, then thoracic duct, the left subclavian vein
- Lymphoedema occurs when drainage obstructed
How does simple oedema occur?
- Oncotic pressure is the colloid osmotic pressure induced by protein in the blood plasma
- Low protein (albumin) states lead to limb swelling and oedema
What are the causes of reduced oncotic pressure?
- Liver failure
- Renal disease= low protein, too much water
- Malnutrition- kwashiorkor (severe protein deficiency)
Describe inflammation
- Vasodilation a arteriole level
- Opening pre-capillary sphincter
- More permeable capillaries
- Swollen, hot tissue
Describe lower limb cellulitis
Hot swollen leg
Tissue oedema
Chronic cellulitis= lymphatic obstruction
Describe right ventricular failure
- Central venous pressure rises
- Peripheral venous pressure rises
- Increased interstitial fluid
- Oedema
