Vasc- hemodynamics Flashcards
(41 cards)
when distended the cross-sectional area of the vein is how much larger than the corresponding artery?
3-4 times that of a corresponding artery
veins contain what fraction of the blood in the body?
2/3rds
role of calf muscle pump?
- aids in the return of blood from the legs against the force of gravity
what do the muscles act as?
a power source
contraction of the calf muscles can generate hoe much pressure?
> 200 mmHg
increased hematocrit increases?
viscosity
the venous system is what type of pressure system?
low pressure system
The venous pressure of the lower limbs is comprised of what 3 main components?
- hydrostatic (gravitational) pressure
- residual pressure
- muscular and respiratory pressure
what is hydrostatic pressure?
- due to the height of the venous blood column
- applies to a patient in a standing position
- flow from the furthest points (feet) must return to the right atrium
in the lower limbs- the main resistance to flow is due to?
- microcirculation
define residual pressure
At the venous end of the capillaries, the venous pressure supplied by the arterial pressure is called residual pressure
purpose of augmentation***?
Venous flow can be augmented to observe a large bolus of blood flowing through a vein in an unobstructed vessel
veins are compressible due to?
- a thinner muscular wall
- can rule out clot this way
what affects venous flow? **** (6)
- Respiratory variations
- Cardiac function
- Calf muscle pump
- Competent venous valves
- Venous pressure
- Exercise
hereditary risk factors of DVT? *****
blood disorders:
Antithrombin deficiencies
Elevated clotting factors
Plasminogen deficiency
Prothrombotic disease
acquired risk factors of DVT?
Age,obesity Advanced malignancy Recent surgery Trauma Immobolization Pregnancy O.C. use
what 3 things are included in virchow’s triad?
- Endothelial damage
- Venous stasis (suggests slow blood flow) ex. Long car ride, immobile
- Hypercoagulable state
S/S of DVT **?
- Lower extremity swelling
- Pain
- Positive Homan’s sign-pain on forced dorsiflexion of the foot
What is D-dimer test?
- blood test
- measures fibrin degradation products that accumulate in the blood when thrombus forms
DVT is unlikely if D-dimer is?
negative
what can cause a false positive d-dimer?
- not helpful in patients over 80
- hospitalized
- pregnant
- cancer
what is acute thrombus look like?
- Faintly echogenic, almost invisible
- Detected by limited compression and faint visible edge of clot
- Attached to the vein wall over short-area
- May have a long snakelike clot swaying back and forth in the lumen
- These poorly attached clots are a risk for emboli
characterization of chronic thrombus?
- complete dissolution of slow over time may occur
- may become more solid
- firmer and more echogenic
- becomes better attached
- less threat of embolization
- large collaterals will develop
5 complications of DVT?
- PE
- incompetent valves
- recurrent DVT
- varicose veins
- chronic venous insufficiency
