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46 Cards in this Set

  • Front
  • Back
What is shock?
Insufficient perfusion of organs resulting from a reduction of blood volume and pressure
What are 3 Key changes that occur in response to hemorrhagic shock?
1. High sympathetic output
2. Shunting of blood to vital organs
3. Decreased blood pressure
Where is blood shunted in response to hemorrhagic shock?
From splanchnic and muscular circulations to the vital organs - brain and heart.
4 Main types of shock:
1. Hemorrhagic
2. Cardiogenic
3. Anaphylactic
4. Septic
4 key points about shock:
-Vital organ hypoperfusion
-Assoc w/ reduced MAP
-High sympathetic tone
-Volume/Time dependent
Stages of shock:
1. Nonprogressive (compensated)
2. Progressive
3. Irreversible
Which stages can you recover from?
Nonprogressive and progressive

-Cannot recover from irreversible
What happens during nonprogressive shock?
The body's normal compensatory mechanisms kick in and can cause complete recovery.
What happens during progressive shock?
The shock becomes steadily worse until death
What is the deal with irreversible shock?
No form of therapy will save the patient's life.
What is the window of opportunity for volume replacement?
Within 4/5 hrs of hemorrhage
How much blood volume can the body lose and still be ok?
Up to 50%
What happens if you lose 60% of blood vol?
Sympathetic failure - shock is irreversible regardless of volume replacement.
Hallmarks of Hemorrhagic Shock:
-Volume dependence

-Time dependence
What does it mean to say that hemorrhagic shock is volume dependent?
-Up to 20% of vol can be lost with minimal symptoms
-Beyond that the more blood lost the faster CO / AP fall
What falls faster during shock; CO or MAP? Consequence?
CO -> can be misleading because MAP is what you measure and if it's not low yet, you miss the window for volume replacement.
At what %vol lost does CO begin to fall? MAP?
CO - 10%
MAP - 20%
What is the critical percentage of blood loss at which CO and AP will really begin to fall?
What happens at 45% blood loss?
CO/AP fall to zero
What is the "critical threshold"?
The MAP level at which hemorrhagic shock becomes progressive and shock itself will cause still more shock in a viscious pos feedback cycle.
What is the critical threshold?
45% normal MAP
-if arterial pressure falls below 45% of normal, death will occur with time due to symp tone failure.
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
What happens as MAP/CO decrease to cause the vicious cycle feedforward effect?
Coronary bloodflow decreases so that myocardium is not adequetely nourished; weak muscle = even more decreased CO
What is the window of opportunity for recovery from hemorrhage?
4-5 hrs; if volume is replaced within that time the patient will likely recover.
What happens over time if bloodloss is not replaced?
Sympathetic tone fails and the gut takes back its volume - brain and heart are malnourished.
What happens to capillary permeability during progressive shock?
It increases and blood shifts from the vascular space to interstitial.
Most people will survive up to what %age of bloodloss?
5 Processes that make up the Recovery Mechanism during Compensated Shock:
1. Baroreceptor reflex
2. CNS ischemic response
3. Ang II formation
4. ADH release
5. Volume recovery (renal/blood volume regulatn)
So 2 types of control during compensated shock:
How do the Baroreceptors respond to hemorrhagic shock?
-Within sec-min
-Decrease impulses; releases SNS from PNS depression
-Incr HR/contractility
-Vasoconstriction to incr MAP
What is the CNS ischemic response?
The last ditch effort to elicit more powerful sympathetic discharge; does not occur until MAP goes down to 50 mm Hg.
3 consequences of irreversible shock:
-Sympathetic tone failure
-Excessive tissue damage
-Loss of high energy metabolic intermediates (ATP)
What is the cause of septic shock?
Bacterial toxins
5 Characteristics of Septic shock:
-high fever
-marked vasodilation
-Flow problems in microcircultn
Why is CO high in septic shock?
Because there is VASODILATION in infected tissues and elsewhere and this leads to increased VR
What do you have to watch out for in septic shock?
Normal MAP - because of VR / CO not being decreased.
If VR/CO are better in patients with septicemia, why do they have shock and decreased tissue perfusion?
Because the flow problems in microcirculation cause DIC which in turn LIMITS VR and normal tissue flow.
Dehydration shock is what form of shock:
Causes of dehydration shock:
-Excessive sweating
-Diarrhea and vomiting
-Excess renal fluid loss
-Inadequete fluid/electrolyte intake
-Loss of adrenal cortex function
What causes anaphylactic shock?
Histamine from basophils and mast cells.
What are 3 effects of histamine?
1. Arterial dilation
2. Venodilation
3. Increased cap permeability
What is neurogenic shock?
Loss of vasomotor tone w/ massive vasodilation of veins
3 types of neurogenic shock:
1. Deep general anesthesia
2. Spinal anesthesia
3. Brain damage
What is cardiogenic shock?
Decreased ability of heart to pump blood (hypoeffective)
4 causes of cardiogenic shock:
-Toxic heart
-Valve dysfunction
What is the result of decreased CO in cardiogenic shock?
Decreased VR - vicious cycle