CC 3 - Intro to CV Physiology I (Shock) Flashcards
1
Q
What is shock?
A
Circulatory failure (i.e. hypoperfusion) resulting in inadequate perfusion of vital tissues
2
Q
Are the effects of oxygen deprivation due to shock reversible?
A
Initially, yes BUT they rapidly become irreversible
3
Q
What are 4 steps of oxygen deprivation due to shock?
A
- Sequential cell death
- End-organ damage
- Multi-system organ failure
- Death
4
Q
2 types of circulatory shocks?
A
- Caused by decreased CO
2. Without decreased CO
5
Q
2 mechanisms causing decreased CO?
A
- Decreased ability of heart to pump blood
2. Decreased venous return
6
Q
What are 3 potential causes of the heart’s decreased ability to pump blood?
A
- Myocardial infarction
- Severe valvular heart disease (i.e. stenosis)
- Arrhythmias (i.e. AV block)
7
Q
What are 3 potential causes of the decreased venous return?
A
- Diminished BV
- Decreased vascular tone (increased venous volume)
- Obstruction to blood flow
8
Q
What would hypertrophy of the aortic artery cause?
A
Decreased CO
9
Q
What could cause decreased vascular tone?
A
Anaphylaxis
10
Q
Example of obstruction to blood flow?
A
Cancerous tumors in vessels
11
Q
What is IVC or SVC syndromes?
A
Obstruction of vena cavae
12
Q
What are 2 potential causes of circulatory shock without decreased CO?
A
- Excessive metabolism: normal CO is inadequate
- Abnormal tissue perfusion patterns: most of the CO is passing through vessels other than those that supply local tissues with nutrition
13
Q
What is an example of a patient that has excessive metabolic needs?
A
Thyrotoxicosis
14
Q
What is an example of abnormal tissue perfusion patterns? Explain what this is.
A
AV fistula = arteriovenous (AV) fistula: abnormal connection between an artery and a vein
15
Q
What is thyrotoxicosis?
A
= hyperthyroidism
16
Q
What kind of murmur would an AV fistula cause?
A
Continuous murmur
17
Q
Other name for circulatory shock caused by AV fistula? Why?
A
High output heart failure because the CO is elevated
18
Q
What are the 4 types of shock?
A
- Hypovolumic
- Cardiogenic
- Distributive
- Obstructive
19
Q
Other name for distributive shock?
A
Vasodilatory shock
20
Q
3 types of distributive shock?
A
- Anaphylactic
- Septic
- Neurogenic
21
Q
Usual cause of hemorrhagic shock?
A
Trauma
22
Q
What are the 3 major stages of shock?
A
- Nonprogressive stage
- Progressive stage
- Irreversible stage
23
Q
Describe the nonprogressive stage of shock.
A
Normal circulatory compensatory mechanisms eventually cause full recovery without outside help
24
Q
Describe the progressive stage of shock.
A
W/o therapy, shock becomes worse through a vicious cycle of CV deterioration and positive feedback mechanisms that further decrease CO until death
25
Describe the irreversible stage of shock.
Compensatory mechanisms are overwhelmed and shock has progressed to such an extent that all therapy is futile
26
What does shock begin with?
An inciting event:
- Focus of infection (e.g. abscess)
- Injury (e.g. gunshot wound)
27
2 other names for nonprogressive stage of shock?
1. Warm shock
2. Compensated shock
3. Preshock
28
What is preshock characterized by?
Rapid compensation for diminished tissue perfusion by various homeostatic mechanism
29
What % reduction in total effective blood volume can be compensated for by homeostatic mechanisms? Will the patient show symptoms? What does this explain?
10%
Asymptomatic patient
Explains how we are able to donate blood without going into shock
30
What are the 3 clinical signs of preshock?
1. Tachycardia
2. Peripheral vasoconstriction
3. Modest increase or decrease in systemic BP
31
What are the 7 clinical signs of irreversible shock?
1. Tachycardia
2. Dyspnea
3. Restlessness
4. Diaphoresis
5. Metabolic acidosis
6. Oliguria
7. Cool clammy skin
32
Dyspnea?
Difficult or labored breathing
33
Diaphoresis?
Excessive sweating
34
Oliguria?
Production of abnormally small amounts of urine
35
What is the most common cause of shock in the trauma patient?
Hemorrhage
36
2 types of hypovolumic shock?
1. Hemorrhagic
| 2. Dehydration
37
What often happens when there is a femoral artery bleeding? What is this a complication of? What happens if this is not fixed?
Blood will pool in the thigh (up to 1 L) until fascia restricts more blood coming in causing pain
=> complication of angiogram
=> compartment syndrome including tissue ischemia and innervation damage
38
In what 4 locations can massive hemorrhage occur?
1. Chest
2. Abdomen
3. Retroperitoneum
4. Major external wounds
39
What kind of lacerations are often overlooked? Explain
Scalp lacerations can bleed profusely and are often overlooked when significant thoracic or abdominal injuries are present
40
What is the effects of hemorrhage on CO and arterial pressure?
Beyond a 10% decrease in total BV CO and arterial pressure fall until they reach 0 at 45% BV loss
41
In what range of arterial pressure are the carotid sinus baroreceptors stimulated?
60 to 180 mmHg
42
When are the carotid sinus baroreceptors maximally stimulated?
At 180 mmHg
43
Describe the sympathetic NS effect on the vasoconstrictor system of the body to maintain arterial pressure.
1. Constricts arterioles to increase TPR
| 2. Constricts veins and venous reservoirs to maintain venous return
44
In the absence of sympathetic NS mechanisms during shock, what % of BV could be removed before death?
Only 15 to 20% of the blood volume could be removed over a period of 30 minutes before the person dies
45
What is a side effect of HT patients taking alpha adrenergic blockers?
Blocked sympathetic NS => orthostatic hypotension
46
What is one of the most powerful activators of the sympathetic vasoconstrictor system?
CNS ischemic response
47
What is cerebral ischemia?
Decreased blood flow to the vasomotor center of the brain in the lower brain stem
48
Describe the CNS ischemic response.
1. Vasoconstrictor and cardioaccelerator neurons become excited
2. Marked elevation in systemic arterial pressure and some of the peripheral vessels (e.g. kidneys) become totally occluded
3. Bradycardia because the baroreceptor reflex is responding to the very high arterial pressure
49
How high and for how long can the CNS ischemic response elevate the MAP?
250 mmHg for 10 min
50
When does the CNS ischemic response become significant?
When the arterial pressure falls below 60 mmHg
51
When is CNS ischemic response maximally stimulated? What is this called?
Between 15 and 20 mmHg: last ditch stand pressure mechanism
52
What is the effect of sympathetic stimulation on the coronary and cerebral blood vessels?
No effect
53
What regulates blood flow in the coronary and cerebral blood vessels?
Autoregulation maintains flow at a normal level as long as arterial pressure does not fall below 70 mmHg
54
How does hemorrhagic shock pass from the nonprogressive to the progressive stage?
When the degree of hemorrhage crosses a critical threshold, which causes shock to cause even more shock (vicious cycle)
55
What are the 6 compensatory mechanisms in hemorrhagic shock?
1. Baroreceptor reflex
2. CNS ischemic response
3. Reverse stress-relaxation
4. Renin/angiotensin system
5. Vasopressin
6. Restoration of BV by reabsorption of all fluids in the body
56
Explain the reverse stress-relaxation mechanism in response to hemorrhagic shock.
As the blood volume decreases, the stress-relaxation response of blood vessels causes the blood vessels to contract and helps sustain blood pressure (without SNS stimulation)
57
What is the time frame of the sympathetic reflex in response to hemorrhagic shock?
Maximally activated 30 s to 1 min after hemorrhage
58
What is the time frame of the angiotensin/vasopressin mechanisms in response to hemorrhagic shock?
10 min to 1 hr
59
What is the time frame of the readjustement of BV by absorption of fluid in response to hemorrhagic shock?
1 to 48 hrs
60
What causes activation of the sympathetic NS?
Reduced baroreceptor stretch
61
What are the 6 decompensatory mechanisms during shock?
1. Myocardial depression
2. CNS vasomotor failure
3. Thrombosis
4. Tissue ischemia
5. Acidosis
6. Increased vascular permeability
62
What is myocardial depression? What is this called? What can it be due to? Treatment?
Function of the heart is depressed and it has a very low ejection fraction = shock heart
1. Septic shock: the bacteria release cytokines, interleukins, tumor necrosis factors, which damage the heart pump - treatment = antibiotics
2. Ischemic tissues release toxins that have the same effect
63
Is myocardial depression reversible?
YUP
64
Why does thrombosis happen during shock?
Terminal small blood vessels have stasis due to very low flow causing platelet aggregation and thrombosis => further obstruction to blood flow
65
What is increased vascular permeability due to during shock? E.g.?
Bacterial or ischemic toxins
Pneumonia causes increased permeability of the lungs causing pulmonary edema and acute respiratory distress syndrome (ARDS)
66
What is another name for ARDS?
Shock lung
67
What does decreased vasomotor activity of the brain cause?
Vascular dilation
68
How does decreased nutrition of the vascular system affect the vessels?
1. Increased capillary permeability
| 2. Vascular dilation
69
Can transfusion prevent death in irreversible shock?
NOPE (but TBD for sure)
70
Describe how irreversible shock affects cellular high energy phosphate reserves.
Reserves are depleted:
- Liver and heart reserves are diminished
- All the creatine phosphate is degraded
- All the ATP => ADP => AMP => adenosine => uric acid (which cannot reenter the cell)
71
At what rate can new adenosine be synthesized from uric acid? What does this mean?
2% of normal cellular amount per hour
Once high energy phosphate stores are depleted they are difficult to replenish
72
What is the Golden Hour?
In emergency medicine, the Golden Hour is the first 60 min after the occurrence of multi-system trauma which are critical for survival
Even if the patient does not die during that hour there is irreparable damage
73
How many units of blood are needed on any given day in the US?
38,000 units
74
How many units of blood do accident victims may need?
4 to 100 units
75
What are 3 potential causes of neurogenic shock?
1. Brain damage
2. Deep general anesthesia
3. Spinal anesthesia
76
What are 3 potential causes of brain damage?
1. Trauma
2. Stroke
3. Intracranial bleed
77
What is neurogenic shock?
Distributive type of shock resulting in low blood pressure, occasionally with a slowed heart rate, that is attributed to the disruption of the autonomic pathways within the spinal cord
78
What does neurogenic shock cause?
Increased vascular capacity due to sudden loss of vasomotor tone resulting in massive dilatation of the veins
79
What is cardiogenic shock? What is it usually caused by?
Condition in which your heart suddenly can't pump enough blood to meet your body's needs
Usually caused by a heart attack
80
In what % of myocardial ischemia does cardiogenic shock happen?
8.6%
81
What is an anaphylactic shock?
Allergic reaction
82
Describe what happens during an anaphylactic shock.
Basophils and mast cells release histamine and histamine-like substance causing:
1. Venous dilatation => decreased venous return
2. Arteriolar dilatation => decreased arterial pressure
3. Increased capillary permeability
83
How fast can a person die during anaphylactic shock?
Within minutes
84
What is sepsis?
Clinical syndrome characterized by systemic inflammation due to infection
85
What is the continuum of sepsis?
Sepsis => severe sepsis => septic shock
86
Where is septic shock important?
In hospital shock-related deaths
87
How many sepsis cases in the US each year? How many result in death?
750,000:200,000
88
What is the mortality rate of severe sepsis or septic shock?
30 to 60% of patients due within 1 month of the onset of septic shock
89
What are the 5 cardinal findings of shock?
1. Hypotension
2. Oliguria
3. Cool and clammy skin
4. Abnormal mental status
5. Metabolic acidosis
90
How does ARDS appear on an X-ray?
Diffuse, bilateral, alveolar infiltrates without cardiomegaly
91
Mortality due to cardiogenic shock?
60 to 90% (50% in hospital)
92
Mortality due to hypovolemic shock?
Variable depending on cause and time until treatment
93
Shock with highest mortality rate?
Cardiogenic shock
94
Procedure treatment for cardiogenic shock?
Catheter in descending aorta from the femoral artery = intra-aortic balloon pump:
- Expansion during diastole to increase pressure and to increase coronary and cerebral perfusion
- Collapse during systole to decrease the afterload because causes a vacuum in the aorta and sucks the blood out of the ventricle
95
What are the 3 types of shock treatment?
1. Replacement therapy
2. Sympathomimetic drugs
3. Other treatments:
- Head down position by raising legs
- Oxygen therapy
- Glucocorticoids
96
In what condition would you not want to use the intra-aortic balloon pump to treat cardiogenic shock?
Aortic valve insufficiency because it will increase pressure during diastole and more blood will leak back into the heart
97
What are the 3 types of replacement therapies to treat shock?
1. Saline
2. Blood and plasma transfusion
3. Colloid transfusion (albumin, Dextran)
98
During what types of shock are sympathomimetic drugs most useful?
Most useful in neurogenic and anaphylactic shock
99
What are 2 examples of sympathomimetic drugs?
NE and EPI
100
What can be done to patients to ensure all of the ATP does not get depleted (aka what can be done to slow down their metabolism)?
Ice bath to make them very cold
101
What is a STEMI? How many people die of this each year in the US?
ST segment elevation MI or transmural MI
300,000/year
102
What types of shock would be helped by a transfusion to increase BV? What shock would not?
Transfusions will improve preload so for hypovolemic, distributive and preventricular obstructive they may help some but they wont help for cardiogenic shock in which here is already to much preload
