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44 Cards in this Set
- Front
- Back
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How much does intrapleural pressure fluctuate during normal breathing?
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+/- 2
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What happens to CO when you inhale? Why?
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It increases - because you've decreased intrapleural pressure (made it more neg) and made it easier for the heart to pump.
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What happens to CO when you exhale? Why?
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It decreases - because you've increased intrapleural pressure (made it more pos) and now the right atrium needs more pressure to be able to fill.
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What is cardiac tamponade?
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Increased pericardial pressure
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How does cardiac tamponade affect the CO curve?
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It shifts it to the right - CO is decreased
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How is the right shift in CO curve due to cardiac tamponade different from that in exhalation?
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It is more exaggerated at the top - because the external tamponade pressure rises to higher values as the chambers of the heart fill during high CO.
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What does opening the chest cavity do to cardiac output initially? Why?
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Decreases CO from 5 to 2.5 - because of the increase in RAP needed to allow right atrial filling.
But max permissive ability is the same. |
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What happens to CO after opening the chest after time?
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The baroreceptors detect falling MAP, respond by increasing TPR to get CO back up to normal (Psf goes up to about 9).
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What changes are seen in the CO curve as a result of the baroreceptor response? (2)
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1. Psf = 9 via vasoconstriction
2. CO curve is hypereffective (max perm ability ~18) and so CO is now 4 |
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What is the price you pay for the increased CO as a result of compensation for opening the chest cavity?
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Increased right atrial pressure - CO is almost normal (4) but RAP remains about 3.5
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What is the most threatening type of cardiac tamponade?
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Trauma induced hemorrhage
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What effect does Cardiac Tamponade have on transmural pressure?
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It decreases transmural pressure.
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Why does transmural pressure decrease as you increase pressure outside the heart?
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Because normally there is NEGATIVE pressure outside the heart. As that increases (ie pericardial fluid) the gradient decreases.
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What is the initial compensation for cardiac tamponade?
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Sympathetic stimulation
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How does cardiac tamponade effect blood circulation?
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Blood will be shifted to the peripheral circulation because of the loss (hemorrhage) into the pericardial cavity.
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What does the blood shift to periphery do to the CO curve?
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Shifts it to the right b/c of the increased Psf.
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What does the symp stimulation do for the CO curve?
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Not much; CO is not returned all the way to normal and remains depressed.
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What does the cardiac tamponade curve look like in contrast to all the other curves?
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CURVED - not squarish.
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Does increasing sympathetic output to the heart ALONE have much of an effect on cardiac output?
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NO
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why not?
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Because if you don't have an increased venous return the CO curve is limited to the plateau of the VR curve - 6 L/min
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What is the effect on cardiac output when you stimulate only the peripheral circulation with SNS output, not the heart?
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Much more marked than the heart alone; CO goes up to almost 10 L/min as Psf increases.
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So what are the 2 main effects of increasing sympathetic output?
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1. Makes the heart a stronger pump
2. Increases Psf b/c of periphal vessel contraction. |
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How much does maximal sympathetic stimulation increase Psf? CO?
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Psf = up to 17 mm Hg
CO = up to 11 L/min |
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What happens to the venous return curve as max sympathetic outflow increases Psf?
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The curve becomes much more shallow - due to INCREASED RVR
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What happens to the CO curve with maximal sympathetic stim?
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Max permissive pumping ability is increased by 100% to about 25 L/min
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What does total spinal anesthesia do to the CO/VR curve?
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VR: decreased Psf to 4mmHg
CO: decreased max permissive pumping to about 10 (80% of normal) |
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Why does total spinal anesthesia make the heart such a poor pump?
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Because it knocks out sympathetic output so there is no vasotone of the vessels.
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In general what does AV fistula do?
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INCREASES THE HEART'S EFFECTIVITY
-INCREASED CARDIAC OUTPUT -DECREASES TPR/RVR |
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What is the major change that occurs in AV fistula, curve-wise?
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The VR becomes markedly steeper due to decreased RVR
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What is the initial effect on MAP when the AV shut is opened?
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MAP falls - due to decreased TPR
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What happens as the baroreceptors respond and symp outflow restores MAP to normal?
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The heart becomes more and more effective and CO increases.
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Why does the heart pumping continue to increase in effectiveness?
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Because Psf continues to increase and heart contractility continues to increase with SNS outflow.
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What is the longterm effect of AV fistula, after a few weeks?
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Kidneys kick in to increase blood volume in response to the decreased MAP and SNS stimulation. Prolonged workload on the heart hypertrophies.
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What are the final results of the CO/VR curve for av fistula?
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RAP = 6
CO = 20L/min |
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What does myocardial infarct do to the CO curve in general?
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Shifts it to the right.
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What is the initial effect of MI on the curve?
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-Dramatically decreased max permissive ability
-RAP shifted to +4 mm Hg |
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What happens in response to the decreased CO from MI?
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-Low MAP responded to by baroreceptors
-Cardiac function improves a little -VR shows increased Psf |
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What is the most important compensation for MI in the longterm?
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Renal-Blood volume regulation
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What does Renal-blood volume regulation do for the curve?
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Makes it more effective by increasing Psf.
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What is the price you pay for the increased CO in compensated MI?
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Increased RAP
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What physiological changes occur in circulation during very strenuous exercise?
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-Increased SNS outflow
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What are the 2 reasons for increased VR during strenuous exercise?
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1. Global vasoconstriction of splanchnic/renal bloodflow increases Psf
2. Vasodilation in active muscles reduces RVR |
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What are the 2 reasons for the hypereffective CO curve seen in strenuous exercise?
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1. Increased contractility
2. Increased heartrate |
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How does strenuous exercise affect RAP?
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Hardly at all - it often goes down in fact.
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