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Decreased cardiac output or cardiogenic shock
Cardiac abnormalities that decrease the heart's ability to pump blood
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3 causes of cardiogenic shock
- myocardial infraction
- severe valve dysfunction
- arrhythmias
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What percentage of people who develop cardiogenic shock die?
70%
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3 factors that decrease venous return causing a decrease in cardiac output
- diminished blood volume (hypovolemic shock)
- decreased vascular tone
- obstruction of blood flow
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In the rare case where we have cardiac shock without diminished cardiac out, what two characteristics are to be expected?
- excessive metabolic rate (cardiac output is inadequate to meet demand)
- abnormal tissue perfusion patterns
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Define abnormal tissue perfusion patterns
most of the cardiac output is passing through vessel in which filtration and reabsorption do not occur
**maybe in the case of systemic edema
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What is the result of abnormal tissue perfusion patterns?
A lack of nutrients and oxygen to local tissues
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In most types of shock , ______ blood pressure drops at the same time that _____ output drops.
- Arterial blood pressure
- cardiac output
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Arterial BP and cardiac output dropping at the same time leads to a _____ feedback loop leading to more shock. Explain this feedback loop.
- Positive feedback loop
- Inadequate blood flow to the tissues leads to deterioration. This will include deterioration of the cardiac tissues which decreases cardiac output even more
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Three stages of shock
- Non-progressive stage
- Progressive stage
- Irreversible stage
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Non-progressive stage
normal compensatory mechanisms cause full recovery
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progressive stage
without medical assistance, shock becomes progressively worse leading to death
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irreversible stage
shock has progressed to the point where medical intervention is not effective resulting in death
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Hypovolemic shock
aka hemorrhagic shock: emergency situation in which severe blood loss makes the heart unable to pump blood to the rest of the body
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What percent of blood can be lost before cardiac output declines?
10%
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Compensatory mechanisms can manage to keep _____ pressure normal until about ___% of blood volume loss
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What happens when blood loss reaches 40-45%?
Arterial pressure drops to zero
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The sympathetic reflex to shock?
Increase cardiac output to compensate for more than 10% by increasing contractility
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Sympathetic reflex compensation in shock is the decrease in arterial pressure after bleeding causes a sympathetic ANS response. What is the result (3)
- Vasoconstriction of most arterioles in the systemic circulation increasing total peripheral resistance
- venous constriction to maintain venous return
- increase in heart rate
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In order to compensate from a non progressive hemorrhagic shock, the following factors are implemented by the body. (5)
- baroreceptor reflexes
- CNS ischemic response
- increased secretion of renin and formation of angiotensin II
- increased secretion of ADH
- increased secretion of epinephrine and norepinephrine by the adrenal medulla
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What type of response are your baroreceptor reflexes
sympathetic
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CNS ischemic response is a ____ stimulation that is activated when?
- Sympathetic
- arterial pressure falls below 50mmHg
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Increased secretion of renin and formation of angiotensin II induces what two things?
- vasoconstriction of peripheral arteries
- decreases water loss through the renal system
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Increased secretion of vasopressin stimulates what two things?
- vasoconstriction of peripheral arteries
- water reabsorption by kidneys
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Results of increases secretion of epinephrine and norepinephrine (2)
- vasoconstriction of peripheral arteries
- increase in heart rate
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Two factors that lead to rapid response to hemorrhage in 30 seconds to a few minutes
- sympathetic reflexes
- release of catecholamines
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Which response takes 10 minutes to 1hr?
vasopressin & angiotensin responses
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Exepcted factors of progressive hemorrhagic shock (7)
- cardiac depression
- vasomotor failure
- blockage of very small vessels
- increased capillary permeability
- generalized cellular deterioration
- tissue necrosis in severe shock
- acidosis in shock
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What causes cardiac depression in progressive hemorrhagic shock ?
Blood flow is decreased below what is required to adequately provide nutrients and oxygen to the heart.
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In progressive hemorrhagic failure, how does vasomotor failure occur?
Diminished blood flow to the brain's vasomotor center depresses the center so that it becomes progressively less active and finally shuts down
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The blockage of very small vessels is caused by sluggish blood flow. It leads to ____ of blood and is due to the accumulation of _____ ____ & _____ ____ and other products of ischemic tissues.
- clotting
- carbonic acid & lactic acid
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_____ _____ leads to increased capillary permeability which further reduces _____ _____ as fluid accumulates in tissues.
- Capillary hypoxia
- blood volume
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When does hypoxia induced capillary permeability occur?
In the late stages of prolonged shock
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Which pump is decreased during generalized cellular deterioration? What is the result?
- Na+/K+ pump
- Accumulation of Na+ & Cl- and a loss of K+ in the cell. The tissues then swell due to osmosis
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What are the three other results of generalized cellular deterioration?
- Mitochondrial activity decreases (especially in liver)
- lysosomes begin to break down releasing hydrolases leading to further deterioration
- cellular metabolism decreases
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Two things to expect because some tissues experience greater damage than others during shock due to smaller blood supplies
- Cells nearer to arterial capillaries have better blood flow than venous capillaries
- Lesions may develop in the liver, kidneys, heart and lungs
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Acidosis results from poor oxygen delivery to the tissues. What are 2 expectations?
- cells shift to anaerobic respiration, producing large amounts of lactic acid
- poor perfusion leads to impaired removal of CO2 as well, which also contributes to acidosis
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Irreversible shock
at some point, intervention cannot stop the progression of shock to death
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