Blood Pressure Flashcards

1
Q

Mean blood pressure =

A

(systolic blood pressure +(2x diastolic blood pressure))/3

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2
Q

blood pressure basics

A
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3
Q

What type of flow in the aorta and large arteries?

A

pulsatile

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4
Q

What type of flow in the capillaries and veins?

A

laminar

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5
Q

If systemic arterial blood pressure is too low:

A
  • faint (vaso-vagal attack)
  • shock leading to tissue acidosis (pH<7.35)
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6
Q

If systemic arterial blood pressure is too high, leads to tissue damage

A

too high

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7
Q

Systemic arterial blood pressure is regulated to maintain

A

adequate tissue perfusion

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8
Q

Humans ideal blood pressure

A

120/80 mmHg

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9
Q

State the determinants of blood pressure:

A
  • cardiac output
  • vascular resistance
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10
Q

State the determinants of blood pressure: Cardiac Output:

A
  • amount of blood pumped by the heart: c. 5L/min
  • under hormonal and neurological control
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11
Q

State the determinants of blood pressure: Vascular Resistance:

A
  • predominantly determined by the level of constriction of arterioles
  • under hormonal and neurological control
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12
Q

Blood pressure Equation:

A

cardiac output x stroke volume

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13
Q

Ohm’s Law

A

V=IR

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14
Q

State 3 physical factors that affect blood pressure:

A
  • gravity
  • arterial compliance
  • blood viscosity
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15
Q

Physical factors that affect blood pressure: Gravity:

A
  • blood pressure is higher in feet, lower in head when standing upright….
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16
Q

Physical factors that affect blood pressure: arterial compliance:

A
  • arteries stretch and store elastic potential energy in systole
  • release energy to maintain flow in diastole
  • stiff arteries (eg old age) reduces
    compliance and increases systolic blood
    pressure
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17
Q

Physical factors that affect blood pressure: blood viscosity:

A
  • contributes to resistance to flow
  • high protein/hypercellular blood has high
    viscosity
  • higher pressure to maintain flow
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18
Q

Factors affecting CO and SVR

A
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19
Q

Cardiac output equation

A

CO = HR x SV
heart rate is per min
stroke volume is Liters

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20
Q

Usual cardiac output is

A

c.5L/min

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21
Q

Starling’s Law

A
  • the mechanical energy set free in the
    passage from the resting to the active state
    is a function of the length of the fiber
  • fiber length is determined by end diastolic
    volume (determined by venous return)
  • force contraction is translated into stroke
    volume
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22
Q

Cardiac pressure volume

A
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23
Q

Preload is

A

venous return

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24
Q

preload (venous return)

A
  • circulating blood volume:
    - dehydration, major bleeding
    - kidney failure, over-transfusion
  • Venous tone:
    - autonomic nervous system
    - circulating vasoconstrictors
    - local vasoactive substances
25
Q

Prostacyclin and nitric oxide are

A

vasodilator substances produced by the endothelium that controls local vascular tone

26
Q

Endothelin

A

a vasoconstrictor substance produced by the endothelium that controls local vascular tone

27
Q

Blood =

A

cells + plasma

28
Q

Plasma =

A

water + salt + proteins

29
Q

The kidney can affect blood volume.

A
  • aldosterone (adrenal cortex) - salt
    retention
    - reabsorption in the distal convoluted
    tubule
  • ADH (posterior pituitary) - water retention
    - reabsorption in the distal convoluted
    tubule and collecting ducts
    - released in response to increased
    plasma osmolarity
30
Q

The intrinsic heart rate is

A

set by the sinoatrial node in the right atrium

31
Q

Sympathetic nervous system receptors to increase heart rate

A

Beta-1 adrenogenic

32
Q

What receptor to slow the heart rate

A
  • parasympathetic
  • vagus nerve
  • M2 muscarinic receptors
33
Q

Circulating substances that can affect heart rate?

A
  • adrenaline 9increases) binds to beta-1 receptors
34
Q

control of systemic vascular resistance

A
35
Q

Renin-Angiotensin-Aldosterone System

A
36
Q

Local controls

A

tissue perfusion is autoregulated in response to local need (provide a minimum BP)
- control occurs at arteriole level
- dilation: low O2, high CO2, acidosis, nitric
oxide, prostacyclin
- constriction: endothelin

37
Q

Circulating Catecholamines

A
  • adrenaline and noradrenaline
  • responsible for generalised and sustained
    responses to acute changes
  • receptors:
    alpha: systemic arterioles = vasoconstriction (a1)
    beta: systemic arterioles - vasodilation
    (muscle b2)
    heart - increases rate and force of
    contraction (b1)
38
Q

Noradrenaline is predominantly an

A

alpha agonist

39
Q

Adrenaline is an

A

agonist of both alpha and beta receptors

40
Q

Circulating catecholamines

A
41
Q

Sensors involved in blood pressure:

A
  • baroreceptors: aortic arch, carotid body at the carotid bifurcation
  • signal the brain via:
    - the vagus nerve
    - glossopharyneal nerve
42
Q

Control Centers for blood pressure

A
  • brainstem:
    - cardio-accelerator centre
    - cardio-inhibitory center
    - vasomotor center
43
Q

Purpose of control centers for blood pressure

A

integrate sympathetic and parasympathetic responses

44
Q

Blood pressure: effectors:

A
  • sympathetic nerves:
    - noradrenaline (adrenergic)
    - vasoconstriction (muscle
    vasodilation)
    - increased heart rate and force
  • parasympathetic nerves:
    - acetylcholine
    - vasodilation
    - vagus nerve: decreases heart rate
45
Q

vasomotor center

A
46
Q

Causes of high blood pressure:

A
  • chronic kidney disease
  • structural causes:
    - renal artery stenosis (narrowing)
    - aortic coarctation (narrowing of the
    aorta above the kidneys)
  • Endocrine causes:
    - high aldosterone lvels (conn’s
    syndrome)
    - high catecholamine levels
    (phaeochromocytoma)
    - high cortisol levels 9cushings)
    - high growth hormone (acromegaly)
  • pregnancy/pre-eclampsia
47
Q

hypertension is multifactorial:

A
  • poly genetic
  • obesity
  • high salt intake
  • high alcohol intake
  • ethnicity
48
Q

Effects of chronic hypertension

A
  • heart muscle damage leading to heart failure
  • large vessel damage
  • microvascular damage
49
Q

Effects of chronic hypertension: Large Vessels Damage:

A

Aortic aneurysm (and rupture)
Cerebrovascular disease (stroke)
Coronary artery disease (angina, myocardial infarction)
Peripheral vascular disease (claudication, amputations)

50
Q

Effects of chronic hypertension: Microvascular damage:

A

Kidney dysfunction (CKD)
Brain dysfunction (multi-infarct dementia)
Exacerbates vascular effects of diabetes (kidneys, eyes and peripheral nerves)

51
Q

acute effects of severe hypertension:

A
  • aortic dissection
  • acute heart failure (high afterload)
  • confusion (encephalopathy)
  • cerebral haemorrhage
  • retinal haemorrhage
52
Q

Vaso-vagal episodes

A
  • faints
  • neurally mediated syncope
  • generally reaction to a stressful episode
  • disproportionate parasympathetic activation:
    - arteriolar dilation
    - slow heart rate
  • above lead to fall in BP
  • reduced cerebral perfusion
  • transient loss of consciousness
53
Q

Shock

A

persistently low blood pressure <90mmHg systolic
state of organ hypoperfusion with resultant cellular dysfunction and death

54
Q

Shock leads to

A

reduced perfusion of vital tissues
one inadequate oygen delivery leads to anaerobic metabolism so cellular function declines and can be irreversible leading to death

55
Q

Symptoms of shock

A
  • altered mental status
  • tachycardia
  • hypotension
  • oliguria
56
Q

Diagnosis of shock

A
  • clinical
  • blood pressure <90mmHg systolic
  • measurements of markers of tissue hypoperfusion (blood lactate, base deficit)
57
Q

treatment of shock

A

fluid resuscitation
blood products
correction of the underlyign disorder
vasopressors

58
Q

shock causes

A
  • cardiogenic (large MI) low CO
  • sepsis due to low SVR
  • anaphylaxis due to low SVR
  • low blood volume
  • sympathetic activation: blood flow redistributed to head/heat/muscle
  • poor tissue perfusion: organ malfunction, acidosis