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46 Cards in this Set
- Front
- Back
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What is shock?
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Insufficient perfusion of organs resulting from a reduction of blood volume and pressure
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What are 3 Key changes that occur in response to hemorrhagic shock?
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1. High sympathetic output
2. Shunting of blood to vital organs 3. Decreased blood pressure |
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Where is blood shunted in response to hemorrhagic shock?
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From splanchnic and muscular circulations to the vital organs - brain and heart.
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4 Main types of shock:
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1. Hemorrhagic
2. Cardiogenic 3. Anaphylactic 4. Septic |
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4 key points about shock:
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-Vital organ hypoperfusion
-Assoc w/ reduced MAP -High sympathetic tone -Volume/Time dependent |
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Stages of shock:
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1. Nonprogressive (compensated)
2. Progressive 3. Irreversible |
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Which stages can you recover from?
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Nonprogressive and progressive
-Cannot recover from irreversible |
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What happens during nonprogressive shock?
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The body's normal compensatory mechanisms kick in and can cause complete recovery.
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What happens during progressive shock?
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The shock becomes steadily worse until death
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What is the deal with irreversible shock?
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No form of therapy will save the patient's life.
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What is the window of opportunity for volume replacement?
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Within 4/5 hrs of hemorrhage
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How much blood volume can the body lose and still be ok?
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Up to 50%
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What happens if you lose 60% of blood vol?
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Sympathetic failure - shock is irreversible regardless of volume replacement.
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Hallmarks of Hemorrhagic Shock:
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-Volume dependence
-Time dependence |
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What does it mean to say that hemorrhagic shock is volume dependent?
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-Up to 20% of vol can be lost with minimal symptoms
-Beyond that the more blood lost the faster CO / AP fall |
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What falls faster during shock; CO or MAP? Consequence?
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CO -> can be misleading because MAP is what you measure and if it's not low yet, you miss the window for volume replacement.
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At what %vol lost does CO begin to fall? MAP?
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CO - 10%
MAP - 20% |
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What is the critical percentage of blood loss at which CO and AP will really begin to fall?
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35-45%
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What happens at 45% blood loss?
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CO/AP fall to zero
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What is the "critical threshold"?
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The MAP level at which hemorrhagic shock becomes progressive and shock itself will cause still more shock in a viscious pos feedback cycle.
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What is the critical threshold?
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45% normal MAP
-if arterial pressure falls below 45% of normal, death will occur with time due to symp tone failure. |
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How is the cardiac function curve affected by hemorrhage at:
-2 hrs -4 hrs -5 hrs |
-At 2 hrs there is little deterioration; bit hypoeffective
-At 4 hrs the heart has decrsd to 40% max permissive pumping -At 5 hrs complete and irreversible deterioration |
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What happens as MAP/CO decrease to cause the vicious cycle feedforward effect?
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Coronary bloodflow decreases so that myocardium is not adequetely nourished; weak muscle = even more decreased CO
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What is the window of opportunity for recovery from hemorrhage?
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4-5 hrs; if volume is replaced within that time the patient will likely recover.
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What happens over time if bloodloss is not replaced?
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Sympathetic tone fails and the gut takes back its volume - brain and heart are malnourished.
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What happens to capillary permeability during progressive shock?
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It increases and blood shifts from the vascular space to interstitial.
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Most people will survive up to what %age of bloodloss?
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20
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5 Processes that make up the Recovery Mechanism during Compensated Shock:
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1. Baroreceptor reflex
2. CNS ischemic response 3. Ang II formation 4. ADH release 5. Volume recovery (renal/blood volume regulatn) |
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So 2 types of control during compensated shock:
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-neurogenic
-hormonal |
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How do the Baroreceptors respond to hemorrhagic shock?
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-Within sec-min
-Decrease impulses; releases SNS from PNS depression -Incr HR/contractility -Vasoconstriction to incr MAP |
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What is the CNS ischemic response?
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The last ditch effort to elicit more powerful sympathetic discharge; does not occur until MAP goes down to 50 mm Hg.
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3 consequences of irreversible shock:
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-Sympathetic tone failure
-Excessive tissue damage -Loss of high energy metabolic intermediates (ATP) |
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What is the cause of septic shock?
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Bacterial toxins
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5 Characteristics of Septic shock:
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-high fever
-marked vasodilation -HIGH CARDIAC OUTPUT -Flow problems in microcircultn -DIC |
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Why is CO high in septic shock?
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Because there is VASODILATION in infected tissues and elsewhere and this leads to increased VR
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What do you have to watch out for in septic shock?
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Normal MAP - because of VR / CO not being decreased.
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If VR/CO are better in patients with septicemia, why do they have shock and decreased tissue perfusion?
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Because the flow problems in microcirculation cause DIC which in turn LIMITS VR and normal tissue flow.
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Dehydration shock is what form of shock:
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Hypovolemic
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Causes of dehydration shock:
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-Excessive sweating
-Diarrhea and vomiting -Excess renal fluid loss -Inadequete fluid/electrolyte intake -Loss of adrenal cortex function |
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What causes anaphylactic shock?
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Histamine from basophils and mast cells.
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What are 3 effects of histamine?
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1. Arterial dilation
2. Venodilation 3. Increased cap permeability |
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What is neurogenic shock?
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Loss of vasomotor tone w/ massive vasodilation of veins
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3 types of neurogenic shock:
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1. Deep general anesthesia
2. Spinal anesthesia 3. Brain damage |
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What is cardiogenic shock?
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Decreased ability of heart to pump blood (hypoeffective)
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4 causes of cardiogenic shock:
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-MI
-Toxic heart -Valve dysfunction -Arrythmia |
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What is the result of decreased CO in cardiogenic shock?
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Decreased VR - vicious cycle
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