Week 5 Flashcards
What is hemodynamics
blood flow, motion and the equilibrium under the action of external forces
study of blood flow or the circulation
The cross sectional area of a vein is about _____x that of a corresponding artery.
3-4
How much of the body’s blood does the veins contain
2/3rds
Veins have lower resistances to flow as compared to arteries. True or false
False– veins and arteries have about the same resistance to flow
As the rate of flow increases, the vein becomes _____(more/less) circular , ________ (increasing/decreasing) the resistance.
more, decreasing
What’s the power source that pumps blood back up to the heart?
calf muscles
sinusoids of gastro and soleus muscles and deep/superficial veins play a part
Closure of the valves in the deep veins decreases the length of the column of blood. What does this do to the venous pressure?
reduces it
At rest, blood pools in the legs and is only propelled passively by what? What creates this?
by the dynamic pressure gradient which is caused by the contraction of the LV
Contraction on the calf muscles can generate pressures of
> 200mmHg
Are there valves in the perforating veins?
Yes
What do you call a magic dog
a labracadabrador
Do sinusoids empty or fill with blood with relaxation?
fill
Do sinusoids empty or fill with blood when contracted?
empty
What is it called when red cells stick together which increases the blood viscosity? (slow flow sonographically)
rouleaux flow
Viscosity
thickness of fluid. friction of adjacent fluid layers sliding past one another as seen in blood cells travelling through a vessel
People who are dehydrated, smokers, in high altitudes, have pulmonary fibrosis are all lower availability of oxygen states. This increases what?
blood viscosity
The venous pressure of the lower limbs is comprised of 3 main components:
hydrostatic (gravitational) pressure
residual pressure
muscular and respiratory pressure
Hydrostatic pressure
due to height in the venous column
applies when patient is in standing position
Residual pressure
main resistance of flow is due to microcirculation
at the venous end of capillaries, the venous pressure supplied by the arterial pressure
What acts as an alternate pump to the heart?
calf muscles
When we fill our lungs with air, what happens?
pressure in thorax decreases
abdo pressure increases
flow from lower limbs is impeded
Arterial hemodynamics:
waveform reflects cardiac cycle not affected by respirations high pressure pulsatility: according to vascular bed it supplies has a pulse
Venous hemodynamics:
waveform reflects the respiratory movements
phasicity
low pressure
pulsatility: according to proximity to heart
no pulse
Where do we start seeing not much spontaneous flow?
distal to femV
What affects venous flow?
exercise cardiac function calf muscle pump respiratory variations competent venous valves venous pressure
Risk factors for hereditary blood disorders?
antithrombin deficiencies
elevated clotting factors
plasminogen deficiency
prothrombotic disease
What’s the main component of a clot?
plasma breaking down fibrin
Risk factors for acquired blood disorders?
age, obesity advanced malignancy recent surgery trauma pregnancy OC use immobilization
What’s Virchow’s triad?
this is the three broad categories thought to contribute to thrombosis
endothelial damage
venous stasis
hypercoagulable state
What’s the signs and symptoms of a DVT?
lower extremity swelling
pain
positive Homan’s sign
What is a + Homan’s sign?
pain on forced dorsiflexion of foot
D-dimer assay-
measures fibrin degradation products that accumulate in the blood when thrombus forms
If the d-dimer is negative
DVT is unlikely
What are some d-dimer false positives?
patients over 80, hospitalized, pregnant, and with cancer
Prothrombin time
time it takes for plasma to clot
affected by disseminated intravascular coagulation (DIC), PTT, unexplained bleeding or clotting
used to evaluate hemostasis (process the body uses to form clots and stop bleeding)
