Haemondynamics

Question 1

What is the difference between plasma and serum?

Answer 1

Plasma - liquid part of unclothed whole blood
Serum - (plasma - clotting factors particularly fibrinogen) - clotted whole blood has platelets held with fibrinogen separately

Question 2

What ca cause increase in plasma viscosity?

Answer 2

Marked increase in plasma viscosity can lead to increased whole blood viscoslty and sludging of blood in peripheries. The commonest cause by far is multiple myeloma - too much immunoglobulin produced

Question 3

What can increase while blood viscosity?

Answer 3

Increase in red blood cells (polycythaemia), platelets (thrombocythaemia) or white cells (leukaemia) can can lead to increased whole blood viscoslty and sludging of blood in peripheries

Question 4

What is the difference between plasma viscosity and whole blood viscosity?

Answer 4

,

Question 5

What can be used to “measure inflammation”?

Answer 5

Minor changes in plasma viscosity can result from raised levels of acute phase plasma proteins (e.g. Fibrinogen, Complement factors and C-reactive protein). Acute phase proteins increase in response to inflammation. Therefore, minor changes in plasma viscosity can be used to ‘measure’ the inflammatory response. In recent years, we have been able to measure C-reactive protein (CRP) and this is more commonly used to ‘measure inflammation’

Question 6

What is laminar flow

Answer 6

Blood usually flows in streamlines with each layer of blood remaining the same distance from the wall
The velocity in the centre of the vessel is greater as there is friction at the ends with the wall thus creating a parabolic profile

Question 7

What is turbulent flow?

Answer 7

Blood flowing in all directions in the vessel and continually mixing within the vessel
When the rate of blood flow becomes too great
When it passes by an obstruction in a vessel
When it makes a sharp turn
When it passes over a rough surface
Increases resistance to blood flow

Question 8

What is flow measured in?

Answer 8

Volume per unit time

Question 9

If a vessel is constructed what happens to the flow and energy it carries?

Answer 9

Flow decreases

Energy increases due to velocity increase (ke=1/2mv^2)

Question 10

Describe a descending aorta pressure tracing

Answer 10

See slide

Question 11

What is the anacrotic limb and diacritic limb?

Answer 11

Anacrotic limb - part of graph sloping up = systole

Dicrotic limb - part of graph sloping down = diastole

Question 12

What is pulse pressure?

Answer 12

Pulse pressure = (Peak systolic pressure – end diastolic pressure), which because of the way we measure BP with a sphygomanometer means that:
Pulse pressure = (systolic pressure – diastolic pressure). Therefore most commonly, pulse pressure is (120mm Hg – 80 mm Hg) = 40mm Hg

Question 13

What is mean arterial pressure

Answer 13

Area under curve
Mean arterial pressure can be estimated as (diastolic pressure + 1/3 of the pulse pressure). Therefore most commonly, mean arterial pressure is (80 mmHg + 13 mmHg) = 93 mm Hg. If mean arterial pressure falls below 70 mm Hg then organ perfusion is impaired

Question 14

What is retrograde flow

Answer 14

Opposite direction
Retrograde flow in the arterial system can occur and is greatest when the peripheral resistance is high – the blood ‘bounces back’

Question 15

What is the pulse and what determines the strength of a pulse?

Answer 15

• What we feel is in fact a shock wave that arrives slightly before the blood itself
• The strength or what is also called the volume of the pulse is
determined primarily by two things:
– The force with which the left ventricle is able to eject blood into the arterial system and thus develop a normal shock wave. Reduced pulse volume can result from left ventricular failure, aortic valve stenosis, hypovolaemia (severe dehydration, bleeding). Such a pulse is often described as “thready”
– The pulse pressure. The greater the pulse pressure the stronger the pulse. A strong pulse is often described as ”bounding”

Question 16

What is bradycardia and how does it cause a bounding pulse

Answer 16

Slowing of heart
E.g. heart block
Widens pulse pressure and leads to bounding pulse
Because slowe heart rate -more time before next systolic beat comes in, so there is a longer time for diastolic to go down, which increases the pulse pressure

Question 17

What happens when there is low peripheral resistance/

Answer 17

Lowers diastolic pressure therefore increases pulse pressure 
Bounding 
Eg hot bath, exercise, pregnancy
To remove excess heat 
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