Vasc- hemodynamics Flashcards
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? (4)
- 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
PE symptoms?
- difficulty breathing
- chest pain on inspiration
- palpitations
PE clinically?
- low blood oxygen saturation and cyanosis
- rapid breathing and heart rate
PE- severe cases?
- collapse
- abnormally low blood pressure
- sudden death
diagnosis of PE?
- D-dimer
- CT pulmonary angiography
- pulse oximetry
treatment of PE?
- antigoagulent: heparin and warfarin
PE- surgical intervention?
- pulmonary thrombectomy
what is often the first test performed when PE is suspected?
blood oxygen level
The simplest way to measure blood oxygen levels is with a?
pulse oximeter
what is a pulse oximeter?
It is a noninvasive way to monitor the percentage of hemoglobin that is saturated with oxygen
what is concidered an abnormal saturation level?
- <95%
Post-thrombotic syndrome (PTS)- Vein walls and valves are permanently damaged in what % of cases?
60%
Chronic venous obstruction & reflux manifests as (3)?
- chronic leg swelling
- ankle pigmentation
- ultimately ulcers form
Primary varicose veins?
- abnormally dilated and tortuous superficial veins in the absence of deep venous disease
- History of DVT is rare
- Result of valvular incompetence at SFJ
secondary varicose veins?
associated with obstruction (DVT) or incompetence of the deep venous system valves
what % of DVT’s occur in upper extremity?
10%
what is the most common cause of DVT in upper extremity?
Placement of a VAD
Most common site for central venous access device insertion
subclavian veins and IJV
